EOS

Throughout Earth’s history, so-called volcanic winters have radically altered Earth’s climate. In these events, gases expelled by powerful eruptions form aerosols that reflect the Sun’s radiation and prevent it from warming the planet.

But eruptions’ effects on Earth systems don’t stop with temperature. Large eruptions can have diverse, down-the-line impacts such as altered rainfall, damaged crops, and, according to a new study, disrupted seasonal flood patterns.

The work “builds a bridge between climate modeling work on volcanic eruptions and the potential impacts on people and societies.”

“Usually, when we think about volcanoes, we think of them through the lens of changes in temperature,” said Gabriele Villarini, a hydroclimatologist at Princeton University and a coauthor of the new study. “The question I had was, ‘How about volcanoes and their impact on flooding at the global scale?’”

Villarini and his colleagues simulated the effects of three major volcanic eruptions in Earth’s past. Their results, published in Nature Geoscience, showed an asymmetric pattern: Major eruptions in the tropics of one hemisphere appeared to coincide with substantial increases in seasonal flooding in the opposite hemisphere. The findings could guide disaster response efforts and offer insight into the possible effects of geoengineering as well.

The work “builds a bridge between climate modeling work on volcanic eruptions and the potential impacts on people and societies,” said Matthew Toohey, a climate scientist at the University of Saskatchewan who was not involved in the new study. 

Opposing Hemispheres

The research team used previous simulations of Earth’s climate system to obtain precipitation and temperature data for 5 years after three highly explosive eruptions: Guatemala’s Santa María in 1902, Indonesia’s Mount Agung in 1963, and the Philippines’ Mount Pinatubo in 1991. The scientists also simulated hypothetical control worlds where those eruptions never happened.

Then, the researchers used those data in a statistical model to see how flooding patterns might respond. The model reproduced streamflow conditions after the three eruptions and in the hypothetical cases where the eruptions did not occur.

When volcanic plumes were confined to one hemisphere, the scientists found, peak stream gauge readings increased in the opposite one. (Such readings have long been an indicator of seasonal flooding.)

Mount Agung’s 1963 plume stayed in the Southern Hemisphere. In the year after the eruption, about 50% of stream gauges in tropical Southern Hemisphere basins showed a decrease in peak readings when compared to the noneruption scenario, according to the model. In the Northern Hemisphere, however, about 40% of stream gauges showed an increase in peak flow in the year after the eruption. 

The effects of the eruption of the Santa María volcano in 1902 showed a similar pattern: In the 2 years after the eruption, simulated stream gauges in the Northern Hemisphere (where the aerosols were concentrated) had decreased flows, while those in the Southern Hemisphere experienced an abrupt increase.

The eruption plume from Mount Pinatubo, however, was more evenly distributed across the Northern and Southern Hemispheres, and its effects were distinct. The team’s simulations showed that in the 3 years after the eruption, Pinatubo’s plume decreased flooding in tropical regions but increased stream gauge readings in arid areas of each hemisphere. 

Eruptions on the Equator

The research team didn’t directly identify the underlying reasons for their results, but Villarini said it’s likely the volcanic emissions and flood patterns are linked via the Intertropical Convergence Zone (ITCZ), a band of strengthened precipitation where Earth’s trade winds meet. 

The band of thunderstorms seen here in the area around northern South America marks part of the Intertropical Convergence Zone (ITCZ). The ITCZ is an area of enhanced moisture circling the globe north of the equator. Credit: NASA/GSFC, Public Domain

Gases from volcanic eruptions, especially sulfur dioxide, oxidize to form tiny particles that scatter sunlight, cooling Earth’s surface and creating a temperature differential that pushes the ITCZ away from the hemisphere containing the plume. This shift in the ITCZ likely pushes moisture-laden air into the opposite hemisphere, contributing to increased flooding, Villarini said. 

“If we can make useful predictions about changes in rainfall and changes in streamflow, that can have a real-world impact.”

Toohey said the results are a step toward being able to predict the potential for unusual flooding or drought across broad areas after a volcanic eruption. “It’s important that we keep working in order to understand these processes better, to be able to make better predictions on a finer scale,” he said. 

“If we can make useful predictions about changes in rainfall and changes in streamflow, that can have a real-world impact,” Toohey said.

Villarini said understanding the long-term, secondary impacts of volcanic eruptions also has implications for potential geoengineering efforts. Volcanic eruptions scatter aerosols in much the same way as efforts to cool Earth’s atmosphere via aerosols would. Possible changes to flood patterns would need to be considered by any aerosol engineering efforts, he said. 

—Grace van Deelen (@gvd.bsky.social), Staff Writer

Citation: van Deelen, G. (2025), Volcanic eruptions in one hemisphere linked to floods in the opposite one, Eos, 106, https://doi.org/10.1029/2025EO250349. Published on 22 September 2025. Text © 2025. AGU. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

On Greenland’s coast, glaciers meet the sea in narrow fjords that have been carved over hundreds of thousands of years. Ice cliffs tower hundreds of meters high.

At a glacier’s terminus, where those cliffs crash into the waters of the Atlantic, small (bus-sized) chunks of ice slough off all the time. Occasionally, a stadium-sized iceberg plunks into the water.

All this glacial calving impacts sea level rise and global climate, but there’s a lot that researchers don’t yet know about how calving happens. Now, scientists have gotten a detailed look at the whole process using a fiber-optic cable on the seafloor 500 meters from a glacier’s calving front. The findings were published last month in Nature.

Maneuvering Through the Mélange

Physical processes at the calving front control a glacier’s stability, said Dominik Gräff, a glaciologist at the University of Washington in Seattle who led the new work.

“We don’t have much idea what’s actually going on below the water.”

But gaining access to a glacier’s front can be difficult, and remote sensing methods are able to visualize only the tiny fraction of the ice mass that isn’t submerged. “We don’t have much idea what’s actually going on below the water,” Gräff said.

“It’s always impressive for people to get any observations near the glacier front,” agreed David Sutherland, a physical oceanographer at the University of Oregon in Eugene who did not contribute to the new paper. Researchers working at the front, he explained, risk losing expensive equipment and have to navigate the mélange, a closely packed mix of sea ice and icebergs.

This was the first time fiber-optic sensing was deployed at a calving front. Unlike other methods, such as remote sensing and the use of submerged seismometers, fiber-optic sensing can capture myriad events across a range of times. “It can just sense everything,” Sutherland said.

Gräff and his team dropped a 10-kilometer (6.2-mile) cable on the ocean bottom across the fjord of the Eqalorutsit Kangilliit Sermiat (EKaS) glacier in South Greenland. The maneuver was somewhat tricky. “If you go too slow, the ice mélange that you push open with your vessel [will close] quickly,” Gräff said. “And that prevents your cable from sinking down.”

Julia Schmale, an assistant professor at École Polytechnique Fédérale de Lausanne (left), and Manuela Köpfli, a University of Washington graduate student in Earth and space science, unspool fiber-optic cable from a large drum on the R/V Adolf Jensen, deploying it to the fjord bottom to record data. Credit: Dominik Gräff/University of Washington

Once the cable was in place, researchers were able to collect a wealth of data.

Waves, Wakes, and Cracking

Laser light pulsing through the fiber-optic cable allowed it to function like an entire network of sensors snaking across the fjord.

Acoustic vibrations associated with calving, for instance, stretched and compressed the cable and changed backscattered light signals. Measuring these changes is the basis for distributed acoustic sensing, or DAS.

In addition to measuring acoustics, fiber optics also allowed researchers to measure how light signals change because of temperature, a technique called distributed temperature sensing, or DTS. DAS and DTS allowed researchers to capture calving events that lasted mere milliseconds.

During the 3-week experiment at EKaS, the glass fiber captured 56,000 iceberg detachments.

(1) Initial cracking at EKaS was detected through an acoustic signature traveling through fjord waters. (2) Fractures eventually led to iceberg detachments that emitted seafloor-water interface waves. (3) Detachments caused calving-induced tsunamis at the water surface that caused changes in pressure along the fiber-optic cable. (4) Calving-induced internal gravity waves traveled between layers of fjord water with different temperatures and salinities. (5) Calved-off icebergs drifted away from the glacier terminus, dragging internal wave wakes behind them, agitating the stratified fjord waters and cooling the seafloor. (6) The internal wave wakes caused seafloor currents that generated vibrations in the cable through vortex shedding. (7) Finally, icebergs disintegrated by fracturing, again detected by fiber-optic sensing of acoustic signals. Credit: Gräff et al., 2025, https://doi.org/10.1038/s41586-025-09347-7, CC BY 4.0

That volume of observations meant researchers could trace the calving process from start to finish. It began as cracks formed in glacial ice. Sounds associated with the cracking traveled through the fjord and were picked up by the cable. Then icebergs detached from the glacier, creating underwater waves that traveled between the ice and the sediment below. Iceberg detachments also caused small, local tsunamis that could be identified by pressure changes on the cable at the bottom of the fjord.

In addition to tsunamis and surface waves, the fiber-optic cable was also able to detect internal gravity waves, which travel at the interface between an iceberg’s upper, cold layer of fresh water and the warmer layer of salty seawater below. The EKaS icebergs created wakes as they drifted from the glacier, dragging internal gravity waves behind them and causing circulation in the water. Researchers measured the resulting temperature changes using DTS.

Finally, the fiber-optic cable captured the sounds of icebergs disintegrating. These signals were similar to the initial sound of cracking in the glacier but instead came from the fjord.

Wealth of Data

“There are very few seismological datasets where, within such a short amount of time, you record so many different phenomena.”

“There are very few seismological datasets where, within such a short amount of time, you record so many different phenomena,” said Andreas Fichtner, a seismologist at ETH Zürich in Switzerland who was not part of the work but collaborates with one of the study’s authors. It takes detective work to decode all those signals and assign them to physical processes, he said. “It’s pretty remarkable.”

Gräff and the other researchers hope their rich datasets can improve glacial calving models, which often underestimate the melt that occurs below the surface. Sutherland said it’s not yet clear how to incorporate details from the study into such models, however. Researchers will need to connect the observed processes and the amount of ice lost to factors they can easily measure or estimate, such as ocean temperature and ice thickness, he explained. And they’ll need to study the calving process of different glaciers. EKaS sits on bedrock where it meets the sea, for instance, while other glaciers have a floating terminus.

Still, having a huge set of observations along with information about ocean conditions, which the researchers collected using a suite of other tools, “is pretty powerful,” Sutherland said. “Maybe we can start using this dataset to try to make predictions of when icebergs are going to calve.”

—Carolyn Wilke, Science Writer

Citation: Wilke, C. (2025), A fiber-optic cable eavesdrops on a calving glacier, Eos, 106, https://doi.org/10.1029/2025EO250351. Published on 22 September 2025. Text © 2025. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

Extremely heavy rainfall associated with super typhoon Ragasa could cause the Matai-an landslide dam to overtop in the next two days.

In East Asia, super typhoon Ragasa is moving westwards between Taiwan and the Philippines. At the time of writing, Earth Cut TV has a live feed from the Batanes Islands, almost in the path of the eye (although there is a good chance that data connectivity will be lost in the storm):-

This is an exceptional storm, bringing heavy rainfall and strong winds to a wide area.

The storm has the potential to bring extremely heavy rainfall to southern and eastern Taiwan. There is huge uncertainty as to the magnitude, but reports indicate that the Central Meteorological Administration has estimated that precipitation totals as high as 800 mm could be seen in the mountain areas of Hualien County.

As I have highlighted previously, there is a large valley-blocking landslide at Matai’an in Hualien County, with a large volume of water steadily accumulating. The image below, released by the Hualien Branch of the Forestry and Conservation Department, shows the level of the lake relative to the landslide dam:-

A recent photograph of the Matai’an landslide dam in Taiwan. Image from the Hualien Branch of the Forestry and Conservation Department.

As the image above shows, the freeboard is now quite low.

In consequence, the Forestry and Conservation Administration of the Ministry of Agriculture issued a red alert at 7 a.m. this morning (22 September), mandating the evacuation of vulnerable households downstream. It is estimated that this affects around 1,800 homes.

Should overtopping occur, it is anticipated that 24 September would be the most likely date, so we will need to watch with interest. The Central Weather Administration maintains an exceptional set of web resources recording accumulated precipitation in Taiwan.

Overtopping is not inevitable in the next few days, but that will almost certainly occur in the next few weeks. It is going to be fascinating to see what happens.

Return to The Landslide Blog homepage Text © 2023. The authors. CC BY-NC-ND 3.0
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Craters formed by asteroid impacts are ubiquitous on rocky bodies, and our planet is no exception. Researchers believe they’ve pinpointed yet another impact crater on Earth, this one submerged beneath the North Sea. The structure, known as Silverpit Crater, was discovered roughly 2 decades ago, but its provenance has long been debated. With new subsurface imaging and rock samples, the team concluded that an impact produced Silverpit Crater roughly 45 million years ago. These results were published in Nature Communications.

“People simply didn’t believe it was an impact crater.”

Uisdean Nicholson, a geologist now at Heriot-Watt University in Edinburgh, Scotland, remembered the controversy that swirled around Silverpit Crater back in the late aughts. Was the circular feature lurking beneath the waters of the North Sea under roughly 700 meters of sediments caused by an asteroid impact, or something more plebeian like volcanism or subsidence?

Nicholson, a graduate student at the time, remembered the spirited discussion that ensued among scholars attending a Geological Society of London meeting in 2009. “It was a classic, old-school debate,” he said. The vote came out strongly in favor of a nonimpact origin.

“People simply didn’t believe it was an impact crater,” Nicholson said. It looked as though Silverpit Crater wasn’t destined to join the rarefied group of 200 or so confirmed impact structures on Earth.

Begging for Data

As Nicholson focused his research on other impact structures such as Nadir Crater, he kept thinking about Silverpit. One dataset in particular piqued his interest: a survey of the North Sea seafloor sediments collected in 2022. Those data, amassed on behalf of the Northern Endurance Partnership, a venture to explore carbon capture storage under the North Sea, afforded a close-up look at the 3-kilometer crater and its environs. Previous datasets had also imaged a similar area, but they were of lower resolution and did not cover the entire structure.

A colleague alerted Nicholson about the Northern Endurance Partnership data, and the researchers worked for several months to negotiate access to some of the proprietary observations. “I begged,” Nicholson said.

The researchers were ultimately successful in their quest, and the team pored over high-resolution seismic reflection data revealing faults and buried layers of sediments around Silverpit Crater. “The new data gives a far sharper set of images,” Nicholson said.

The fact that Silverpit Crater is so inaccessible is actually important scientifically, said Matthew S. Huber, a planetary scientist at the Planetary Science Institute in Tucson, Ariz., who was not involved in the research. “Because this crater formed in water and it was buried by sediments in the water immediately after it formed, the whole thing is preserved.”

Faults and Holes

The Northern Endurance Partnership data revealed faults consistent with rock being compacted to varying degrees, as would be expected in an impact. The observations also spotlighted several roughly 10-meter-deep and 250-meter-wide troughs near the rim of the crater. Such scarps could be features eroded by water rushing back into the crater after the impact, the team surmised.

In addition, Nicholson and his colleagues noticed a few pits located beyond the crater rim that were tens of meters deep and wide. “We see all these holes, essentially, around the crater for at least a crater diameter,” Nicholson said. The team thinks that such features are secondary craters, that is, structures formed by material lofted outward from the initial impact.

Secondary craters tend to be rare on Earth because they’re often rapidly erased by erosion after an impact. “We think this is the first really robust terrestrial evidence for secondary cratering,” Nicholson said.

Atomic Wrenching

In 1985, the company British Gas drilled an oil and gas well just a few kilometers northwest of Silverpit Crater. As part of the drilling process, debris excavated from the borehole was pumped to the surface, and some of it was retained for analysis. Nicholson and his colleagues obtained some of those sediments. On the basis of the appearance of tiny marine fossils in rocks from the same depth as Silverpit Crater, the team deduced that the feature formed roughly 43–46 million years ago.

Two mineral grains the team analyzed—one quartz and one feldspar, each roughly the diameter of a human hair—exhibited curious microscopic features. Both grains contained so-called planar deformation features, which are atomic rearrangements of the crystalline structure, Nicholson said. Such wrenching on an atomic scale is indicative of the extreme pressures associated with shock waves.

“This could wind up being a controversial paper within the impact community.”

A celestial object such as an asteroid or comet slamming into a rocky body can readily generate such pressures, but not much else can, Nicholson said. “It’s very difficult to form that any other way.”

The discovery of those shocked grains was a dead giveaway that Silverpit Crater formed from an impact, Nicholson and his colleagues proposed.

These results are convincing, Huber said, but a skeptic might rightfully have some questions. For instance, couldn’t the shocked grains have simply washed into the North Sea from another impact event? “They’ve only found one grain of quartz and one grain of feldspar,” Huber said. “This could wind up being a controversial paper within the impact community.”

—Katherine Kornei (@KatherineKornei), Science Writer

Citation: Kornei, K. (2025), Submerged crater near Europe tied to an impact, Eos, 106, https://doi.org/10.1029/2025EO250275. Published on 20 September 2025. Text © 2025. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

Every year, soils across Thailand are baked hard and bone-dry for months under the unrelenting tropical Sun. But once the long, hot buildup to the monsoon season comes to a head and the rains arrive—typically in May or June—the landscape transforms in a matter of weeks into a patchwork of verdant wetlands.

With this transformation comes a flurry of activity, because many of these wetlands are, in fact, rice paddies ready to be planted. Workers wade through the fields, scattering seed or planting seedlings one by one in the butter soft soil. Months later, as long as these plants have had adequate water and nutrients, they’ll be harvested for their all-important grains.

Rice paddies in Thailand and elsewhere are vital economically and for food security, with rice being the third-most-grown cereal commodity globally. They are also part of the worldwide system of wetlands. From rivers and lakes to marshlands and intertidal flats, wetlands are important ecological and geochemical systems because of the ecosystem services they provide: biodiversity, natural pollution remediation, carbon sequestration, and protection against storm surges, to name a few.

Worachart Wisawapipat of Kasetsart University checks the condition of the soil at a rice paddy experiment site in northeastern Thailand. Credit: Kurt Barmettler

Rice paddies are also of special interest to geochemists, because the regular seasonal pattern of flooding and drainage in many paddy fields makes them ideal natural laboratories in which to study soil biogeochemical processes. Indeed, in several locations in Thailand in 2021, scientists from the Swiss Federal Institute of Technology (ETH Zurich) and Kasetsart University in Bangkok joined the workers in the fields as the growing season began. The scientists were there to plant not rice, though, but iron minerals, with the purpose of testing a new method for investigating how cycles of wetting and drying contribute to these minerals’ reactivity in soil.

A Linchpin of Soil Functioning

Iron is a linchpin of chemical cycling in the environment.

Iron is usually among the most abundant elements in soils, and it is a linchpin of chemical cycling in the environment. It’s thus of critical interest to farmers concerned with the availability of nutrients to their plants, engineers determining risks posed by toxic elements in soil, and land managers wanting to understand soil carbon storage. For several reasons, iron more often than not significantly controls how soil nutrients and toxic elements behave, how carbon is stored, and how other chemical processes play out in soils.

One reason is that iron is reactive in a variety of environmental conditions. In contact with air, oxidized forms of iron—including the yellow-brown to orange oxyhydroxide minerals commonly recognized as rust—are most stable and abundant. When a soil is flooded and the flow of oxygen through it is restricted, some of these minerals may dissolve. This dissolution occurs because some microorganisms can use iron minerals as an alternative to oxygen in the reduction and oxidation (redox) reactions they rely on for energy. In other words, some microorganisms essentially breathe redox-active iron (see video below), reducing oxidized iron and converting it to other forms.

Iron is also very versatile and combines with many other chemical elements to form a wide variety of minerals such as oxyhydroxides, carbonates, phosphates, sulfides, hydroxysulfates, and others that can host trace elements in their structures. What’s more, iron mineral particles tend to be very small and have large surface areas that allow them to bind other compounds. This property also makes iron mineral particles susceptible to rapid change under evolving environmental conditions.

Following Mineral Transformations in Field Soils

Studying the behavior of iron in soils using measurement techniques that are not specific to iron is challenging. The relatively small signatures of iron minerals are often overshadowed by those of the much more abundant silicate minerals that make up the bulk of soil mass.

With techniques that do selectively detect iron in soil, such as synchrotron X-ray absorption spectroscopy, researchers can follow changes in the composition of a whole soil sample, but not changes in a single target mineral. And if the complexity of the surrounding soil is stripped away to perform simplified laboratory experiments focusing on iron minerals, the mineral transformations observed do not always reflect what happens in natural soils.

Katrin Schiedung of ETH Zurich takes soil samples in a flooded rice paddy in northeastern Thailand. Credit: Ruben Kretzschmar

Iron minerals enriched in iron-57 and having precisely controlled properties can be synthesized in the laboratory, then mixed into soils to undergo reactions similar to those of natural iron minerals.

To overcome the challenge of tracing iron mineral transformations in soil, we developed a new approach using a stable isotope of iron to label synthetic minerals. Iron-57 occurs naturally, making up about 2.1% of the iron in soils and exhibiting the same chemical behavior as other naturally occurring iron isotopes (iron-54, 5.8%; iron-56, 91.8%; iron-58, 0.3%). Iron minerals enriched in iron-57 and having precisely controlled properties can be synthesized in the laboratory, then mixed into soils to undergo reactions similar to those of natural iron minerals. Even if the experimental enrichment of iron in the soil is small, the iron-57 is predominantly present in the synthetic minerals, allowing us to focus specifically on what happens to those minerals.

We chose iron-57 as a tracer in our experiments because of the ability to analyze it using Mössbauer spectroscopy. This technique, based on Rudolf Mössbauer’s fortuitous (and 1961 Nobel Prize–winning) discovery of recoilless nuclear resonance fluorescence, is sensitive to the redox state and chemical environment around iron-57 atoms in a sample. Crucially, all other isotopes of iron are invisible using this technique.

Mössbauer spectroscopy has been widely used in the Earth sciences, including for mineralogical analyses of soil samples and Martian rocks. In our application, adding iron-57 minerals into soils and tracing them with Mössbauer spectroscopy allows us to follow otherwise hidden mineral transformations (Figure 1).

Fig. 1. In the newly developed method, iron-57-labeled (57Fe-labeled) synthetic minerals are used to enrich a natural soil sample, which is placed in a porous mesh bag so it can still interact chemically with the surrounding soil. Following the experiment, Mössbauer spectroscopy, which irradiates the sample with gamma rays of a frequency that interacts only with iron-57, is used to measure the transformation products of the labeled minerals.

After adding portions of synthetic jarosite (a potassium-iron hydroxysulfate) or ferrihydrite or lepidocrocite (both iron oxyhydroxides) to small plots in the Thai rice paddies early in the growing season, we went back several times until the end of the season 4 months later to collect soil samples for analysis.

The mineral transformations we observed with Mössbauer spectroscopy were dominated by the dissolution of the added minerals and the release of reduced iron into soil pore water. Proximity to bacteria in the soil promoted mineral dissolution, and some of the released iron either remained dissolved or was trapped on soil particles. New minerals that formed—including green rust, a highly reactive hydroxide mineral that is usually difficult to detect in the environment—tended to be nanocrystalline in size and often contained both reduced and oxidized forms of iron.

Joëlle Kubeneck of ETH Zurich removes a sediment core from the intertidal wetlands of Germany’s Wadden Sea. Credit: Ruben Kretzschmar

Such results can shed light on biogeochemical cycling that affects ecosystem processes. Dissolution of iron minerals might lead to releases of associated pollutants, nutrients, or carbon compounds, for example. On the other hand, we observed that many of the reaction products in soil are nanocrystalline minerals, which have large reactive surface areas that might adsorb dissolved compounds such as metals.

We have also applied this new approach to understand a range of iron mineral transformation processes in soil and sediment environments other than rice paddies. In sediments along Germany’s north coast, for example, we observed the in situ formation of vivianite, a reduced iron phosphate mineral, in a matter of weeks. Phosphorus in vivianite has limited bioavailability, so formation of the mineral can control the availability of phosphorus in the environment and potentially reduce the risk of eutrophication. In addition, we have used the method to study oxidation reactions of reduced iron minerals, sulfidization of vivianite and lepidocrocite leading to the formation of iron sulfide minerals like greigite, and interactions between iron and organic matter during redox cycles.

An Array of Applications

Iron minerals are ubiquitous in natural environments and are used in many engineering applications. We anticipate that iron-57 labeling of minerals coupled with Mössbauer spectroscopy, although applied only to soils so far, could help to answer questions about transformations of these minerals in other domains of the Earth sciences and beyond.

Using iron-57 tracers could contribute to studies on the origins of iron mineral assemblages in sedimentary deposits on Earth or other astronomical bodies such as Mars.

Using iron-57 tracers could, for example, contribute to studies on geological processes, including weathering or metamorphism, or on the origins of iron mineral assemblages in paleosols and other sedimentary deposits on Earth or other astronomical bodies such as Mars.

Experiments with iron-57-labeled minerals could also help to understand redox-driven iron mineral transformation processes at work in applied geoscience technologies. In pollution management, for example, permeable reactive barriers containing iron are a tool for mitigating the spread of contaminants in groundwater. Another example involves geological deposits of redox-active iron minerals that may be used to store or produce hydrogen as a clean energy source.

Outside the Earth sciences, potential applications of iron-57-labeled synthetic minerals exist in fields as diverse as corrosion science, construction engineering, and experimental archaeology. The formation of rust on iron-bearing objects is the outcome of many interrelated chemical processes. Iron-57 tracers may help to follow and unravel those corrosion processes. They could also probe effects of different metal alloy compositions and exposure environments in tests of the longevity of steel infrastructure or of conservation methods for historical artifacts.

For now, our findings from the synthetic iron minerals we’ve “planted” in rice paddy soils are shaping understanding of the chemistry of periodically flooded soils, revealing that just like plants, the life cycles of iron minerals depend on the composition of and conditions in the soil. With continuing research in soils and with new applications focused on other natural and engineered environments, scientists can gain needed insights into how iron in its many forms affects vital issues from soil health and pollution transport to carbon storage and energy production.

Acknowledgments

This research was carried out as part of the European Research Council–funded IRMIDYN (Iron Mineral Dynamics in Soils and Sediments) project at ETH Zurich. The research was led by Ruben Kretzschmar with team members Laurel ThomasArrigo, Katherine Rothwell, Luiza Notini, Katrin Schiedung (published as Katrin Schulz), Joëlle Kubeneck, Andrew Grigg, Pierre Lefebvre, Sara Martinengo, and Giulia Fantappiè, while each was affiliated with the Institute of Biogeochemistry and Pollutant Dynamics at ETH Zurich, in Switzerland. We acknowledge important contributions to the research made by Kurt Barmettler (ETH Zurich) and Worachart Wisawapipat (Kasetsart University).

Author Information

Andrew R. C. Grigg (andrew.grigg@usys.ethz.ch), Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, Zurich, Switzerland; Katrin Schiedung, Thünen Institute, Braunschweig, Germany; Joëlle Kubeneck, TNO–Geological Survey of the Netherlands, Utrecht; also at Radboud University, Nijmegen, Netherlands; and Ruben Kretzschmar, Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, Zurich, Switzerland

Citation: Grigg, A. R. C., K. Schiedung, J. Kubeneck, and R. Kretzschmar (2025), Tracing iron’s invisible transformations just beneath our feet, Eos, 106, https://doi.org/10.1029/2025EO250347. Published on 19 September 2025. Text © 2025. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

Two billion years ago, a massive star exploded. When its light reached Earth in 2021, it joined more than 20,000 recorded supernova candidates observed that year.

This one was unique, however. It exhibited features not shared by any other known stellar explosion: The star had shed almost all of its outer layers before it died, exposing a core rich in silicon and sulfur.

SN 2021yfj, as this supernova is labeled, revealed never before seen details about stellar interiors. Precisely how a star could die this way is a marvelous puzzle that may help researchers learn about the deaths of the most massive stars and how they spread new elements through the cosmos.

“By studying supernovae, we can develop ideas of how stars form, evolve, and die,” said Steve Schulze of Northwestern University in Illinois, who led the observations and analysis of SN 2021yfj, published in Nature.

Onions Have Layers, Stars Have Layers

All stars, including the Sun, spend the majority of their life cycles fusing hydrogen into helium in their cores, which are surrounded by a hydrogen plasma envelope. When this fuel is exhausted, the core contracts and begins fusing helium into carbon and oxygen. For the most massive stars (those at least 8 times the mass of the Sun) this process continues to fuse heavier and heavier elements in the core.

The result is an onion-like (or ogre-like) character of aging high-mass stars: a hydrogen envelope surrounding a shell of helium, around a shell of carbon and oxygen. Layers of neon, magnesium, silicon, sulfur, and higher-mass nuclei form deeper toward the core. Eventually the energy produced by fusion is no longer able to maintain the core’s integrity, at which point the star explodes as a supernova.

This is the story theory tells, at least; these shells aren’t visible to telescopes. Astronomers must deduce the makeup of interiors from the spectrum of light stars emit when they explode.

“The spectra of supernovae are their fingerprints.”

“The spectra of supernovae are their fingerprints,” said Maryam Modjaz, an astronomer at the University of Virginia who was not involved in the study. She called this type of research stellar forensics. “We see the explosion of the star and we work backwards.”

However, very massive stars shed a great deal of their outer envelopes long before they explode, as astronomers observed during the dramatic dimming of Betelgeuse in 2019. Some extremely massive specimens known as Wolf-Rayet (pronounced “rah-YAY”) stars expel their envelopes much earlier in their lifetimes. The most commonly observed type of Wolf-Rayet stars consist of a hydrogen nebula swathing the extremely hot layers surrounding the core, which is dominated by emissions from helium and carbon.

I Like That Spectrum—That Is a Nice Spectrum

SN 2021yfj took this early-shedding process further than any other star yet observed: It had shed not only its hydrogen envelope, but also its helium, carbon, and oxygen shells. The spectrum Schulze and his colleagues measured exhibited emissions from ionized silicon and sulfur, indicating the progenitor had ejected that layer before exploding.

“The progenitor star [of supernova 2021yfj] had essentially lost almost all of its shells,” Schulze said. Astronomers have observed other stars that have been stripped of their outer layers, but never to this extreme.

“We have spectra from hundreds of thousands of supernovae, [and] this is the first time we’ve seen deep into the guts of a dying star.”

Though that provided strong evidence supporting the onion model for high-mass stars, it also was surprising: Nobody expected a star to shed that much material before going supernova.

“We have spectra from hundreds of thousands of supernovae, [and] this is the first time we’ve seen deep into the guts of a dying star,” Modjaz said. “This must be a very unique, very uncommon explosion and therefore [uncommon] progenitor.”

“The properties of supernova 2021yfj are so extreme that it’s challenging to find a model that can describe all of the observations,” Schulze said.

“Our leading hypothesis or leading idea,” he continued, “is that it was a very massive star, around 60 times more mass than the Sun.” Because it had already shed its hydrogen and helium by the time it was observed, though, the star was probably even more massive when it was born. He cautioned against trying to make too many guesses based on the data so far. “Exactly how massive it was will require very detailed simulations [and] the development of models that don’t exist yet.”

Schulze noted that even with hundreds of thousands of identified supernovae, astronomers have yet to see all the possible types. To make things more challenging, supernovae—bright as they are—are single points of light that fade over a matter of days, so spotting them often involves a degree of luck. Extreme stripped-core supernovae are so rare, just by probability astronomers will find tens of thousands more typical explosions before the next example turns up in their data.

However, that task is less daunting than it sounds.

In addition to the Zwicky Transient Facility where astronomers detected SN 2021yfj, Schulze and Modjaz both hailed the Vera C. Rubin Observatory, which is expected to detect a thousand supernovae each night of operation when it comes online in 2026. Though that telescope isn’t being built for spectroscopy, its ability to scan huge swaths of the sky at once will let astronomers identify explosions to analyze in more detail quickly, bringing us closer to an understanding of how massive stars live and die.

—Matthew R. Francis (@BowlerHatScience.org), Science Writer

Citation: Francis, M. R. (2025), This star stripped off its layers long before exploding, Eos, 106, https://doi.org/10.1029/2025EO250340. Published on 19 September 2025. Text © 2025. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

Local reports suggested that over 1,500 people died in this event, and a high death toll was reported by some international agencies. However, examination of satellite imagery casts significant doubt on this interpretation.

It has been widely reported that on 31 August 2025, a devastating landslide occurred at Tarasin (there are various spellings of this place) in the Marrah Mountains in Central Darfur, Sudan. Initial reports indicated that 1,000 people had been killed, making this the most deadly landslide of 2025 to date, whilst subsequent reports elevated this number to over 1,500. The reports were given credence by organisations such as Save the Children, who reported that 373 bodies had been recovered. There was only one reported survivor of the disaster.

However, it should also be noted that this very high total was not supported by government reports – noting of course that Sudan has extensive civil conflict, and that this area is not controlled by the government. BBC Verify examined the event too using Maxar satellite data, but could not identify a village that had been destroyed. The Washington Post reported that the United Nations subsequently reduced their estimated total loss of life to “scores”. On Bluesky, Dan Shugar pointed out that the reporting of 1,000 fatalities does not really stack up. The HydrologyNL Bluesky account has also posted some interesting analysis of this event.

The location of this landslide event is [13.01697, 24.38774]. This is a Planet image of the site draped onto the Google Earth DEM:-

Satellite image of the aftermath of the 31 August 2025 landslides in Sudan. Planet image draped onto the Google Earth DEM. Image copyright Planet, used with permission. Image dated 6 September 2025.

The marker highlights the rear scarp of the largest failure, although there are several landslides in the image. These landslides correlate with images from the site posted by news organisations (there are some images of unrelated landslides too, plus some AI slop). It appears that there have been multiple shallow landslides than have transitioned into channelised debris flows.

And this is a Google Earth view, with imagery from 2023 (with some cloud), showing the same area:-

The site of the 31 August 2025 landslides in Sudan. Google Earth image from 2023.

Some local reports of these landslides suggest that 1,500 houses were destroyed, based on information from the Sudan Liberation Movement. However, it is also notable that none of the published photography shows destruction on this scale. And the Google Earth images do not show any large settlements in the path of either the landslides themselves or the channelised debris flows. There is a cluster of houses at the foot of the main failure that has been destroyed:-

A cluster of buildings subsequently destroyed by the 31 August 2025 landslides in Sudan. Google Earth image from 2023.

However, this is a small number of buildings, not on the reported scale of losses. I have also looked at the Planet imagery from just before the landslide. There is no evidence of a large settlement in this area.

Thus, a reported death toll of 1,000-1,500 seems highly improbable, and the loss of 1,500 houses is not supported by the imagery or photography.

So, what are the possible explanations? We might consider the following:

1. The location is wrong – and the reports describe an event somewhere else. I consider this to be low probability, given the images that have been published;
2. Dan Shugar suggested that perhaps some sort of social event occurred in the path of the landslide – a wedding or suchlike. But the local reports are of 1,500 houses lost, and in general my experience is that this type of circumstance is reported, given the nature of the tragedy. Again, low probability.
3. The losses occurred a long distance down the channel. I cannot find such a site on the imagery, and I would expect that the location would be reported, and that photography would show the devastation. Again, this would seem to be low probaility.
4. There is mis-reporting, either accidentally or deliberately. I consider this to be high probability.

In remote areas, we have previously seen vastly inflated estimates of loss of life – a recent example was the 24 May Kaokalam landslide in Papua New Guinea. This can simply be a misunderstanding or the result of rumours. On the other hand, it can be deliberate. For example, loss of life can be inflated to attract additional resource for a population that is suffering extreme poverty, or it can be an attempt by the local forces to attract supplies for their own purposes. Others will be able to judge the most likely explanation.

I’m struggling to understand why reputable international agencies would appear to support these inflated reports, especially where they appear to provide testimony from the site.

Reference

Planet Team 2025. Planet Application Program Interface: In Space for Life on Earth. San Francisco, CA. https://www.planet.com/

Return to The Landslide Blog homepage Text © 2023. The authors. CC BY-NC-ND 3.0
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In 2018, the Hayabusa2 mission successfully encountered asteroid Ryugu. The Japan Aerospace Exploration Agency (JAXA) spacecraft arrived at, touched down on, collected samples of, and lifted off from the asteroid. It returned samples to Earth in 2020.

With plenty of fuel left for its extended mission, called Hayabusa2# or “Hayabusa2 Sharp,” the spacecraft raced off to its next objective, a high-speed flyby of asteroid 98943 Torifune in 2026. If all goes well with that rendezvous, the craft will attempt its final objective: an encounter with and touchdown on asteroid 1998 KY26 in 2031.

But that final objective may prove more difficult than initially imagined. New ground-based observations of 1998 KY26 have revealed that the asteroid is 3 times smaller than previously thought and spins twice as fast.

“We found that the reality of the object is completely different from what it was previously described as,” Toni Santana-Ros, lead author of a new study on 1998 KY26 and an asteroid researcher at Universidad de Alicante and Universitat de Barcelona in Spain, said in a statement.

Small and Fast

Astronomers discovered 1998 KY26 in 1998 when it came within 2 times the Earth-Moon distance. Radar and visual observations shortly after discovery estimated that the asteroid was about 30 meters across and rotated once every 10.7 minutes, the fastest-rotating asteroid known at that time. As the asteroid moved away, it became too faint to see for more than 2 decades. When Hayabusa2’s mission scientists selected targets for its extended mission, they relied on those 1998 calculations.

The asteroid completes one spin every 5 minutes and 21 seconds, less time than it takes to listen to Queen’s “Bohemian Rhapsody.”

Finally, in 2024, 1998 KY26 came close enough to Earth—12 times the distance to the Moon—to observe again. Using four of the most powerful ground-based telescopes available, Santana-Ros and his colleagues watched the diminutive asteroid tumble and spin from multiple angles, allowing them to calculate a more accurate spin rate than was possible with the limited radar and photometry in 1998.

They calculated that the asteroid completes one spin every 5 minutes and 21 seconds, less time than it takes to listen to Queen’s “Bohemian Rhapsody.” The team then combined those new observations with the 1998 radar data to recalculate the asteroid’s size. They found that instead of being roughly 30 meters in diameter, 1998 KY26 is just 11 meters, or about the length of a telephone pole. The team published these results in Nature Communications on 18 September.

Asteroid Ryugu (left) is roughly 82 times the size of asteroid 1998 KY26 (right). Credit: ESO/M. Kornmesser; Asteroid models: T. Santana-Ros, JAXA/University of Aizu/Kobe University, CC BY 4.0

“The smaller the asteroids get, the more abundant they are—but that also means that they are harder to find,” explained Teddy Kareta, a planetary scientist at Villanova University in Pennsylvania who was not involved with the new discovery. “The fact that this new paper finds such a small size for KY26 is tremendously interesting on its own—Hayabusa2 will be able to explore an extremely understudied population—but it also means that we might not have a tremendous number of known objects to compare to as well.”

A Challenge and an Opportunity

The new size and spin measurements of 1998 KY26 will make Hayabusa2’s planned touchdown more challenging, the researchers wrote. However, this is not the first time that an asteroid rendezvous mission has had to adjust its expectations mid-flight. Both Ryugu and Bennu, the first target of NASA’s Origins, Spectral Interpretation, Resource Identification, Security–Regolith Explorer (OSIRIS-REx) mission, had rougher surfaces than expected, requiring the respective missions to adjust their sample collection methods. Too, the OSIRIS-REx team learned that Bennu was actively spitting out material only when the spacecraft got close, which led them to change their plan for orbital insertion.

Despite the new challenges with 1998 KY26, Hayabusa2#’s team has a big advantage: 6 years to rework their game plan.

“The Hayabusa2 team are incredibly smart, hardworking, and have a ton of experience under their belts, but I’m sure that this kind of result is causing a bit of hand-wringing and concern for them even if the spacecraft is fully capable,” Kareta said.

“We have never seen a ten-metre-size asteroid in situ, so we don’t really know what to expect and how it will look.”

“I’m sure even the team has their doubts about whether or not the original plan was possible, but if I had to bet money, I still think the team will try [to touch down],” they added. “You set yourself up for success by building a great spacecraft and collecting a great team of engineers and scientists to staff it, but it’s still a bet every time you try something new.”

Even if a touchdown on 1998 KY26 ultimately proves impossible and Hayabusa2# simply flies on by, asteroid scientists will still gain valuable information about an incredibly common but hard-to-spot type of small asteroid.

“We have never seen a ten-metre-size asteroid in situ, so we don’t really know what to expect and how it will look,” Santana-Ros wrote.

“In many ways, a spacecraft visit to it now is even more exciting than it was before,” Kareta said.

—Kimberly M. S. Cartier (@astrokimcartier.bsky.social), Staff Writer

Citation: Cartier, K. M. S. (2025), Hayabusa2’s final target is 3 times smaller than we thought, Eos, 106, https://doi.org/10.1029/2025EO250353. Published on 18 September 2025. Text © 2025. AGU. CC BY-NC-ND 3.0
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Source: AGU Advances

Streamflow drought—when substantially less water than usual moves through rivers—can seriously disrupt the welfare of nearby communities, agriculture, and economies. Synchronous drought, in which multiple river basins experience drought simultaneously, can be even more severe and far-reaching.

Recent observations and modeling suggest that on the Indian subcontinent, where major rivers support more than 2 billion people, the likelihood of synchronous drought is increasing as summer monsoons weaken, the Indian Ocean warms, and anthropogenic emissions and excessive groundwater pumping continue. However, little is known about the long-term patterns of synchronous drought in India, in part because streamflow data don’t offer information about the distant past.

By combining several decades of streamflow measurements from 45 gauge stations along India’s major rivers with high-resolution temperature and precipitation data and data from a range of paleoclimate proxies, Chuphal and Mishra have now reconstructed streamflow records across more than 800 years.

To look farther back in time, the researchers turned to the Monsoon Asia Drought Atlas, which comprises tree ring data indicating summer drought conditions across Asia between 1200 and 2012. They also considered historical records of climate patterns like El Niño, the Pacific Decadal Oscillation, and the Indian Ocean Dipole to explore connections among drought frequency, reoccurrence, and synchronicity. And they used two models from the Paleoclimate Modeling Intercomparison Project Phase 4 (PMIP4) that are part of the Coupled Model Intercomparison Project Phase 6 (CMIP6) to simulate precipitation and temperature data, as well as a hydrological model to simulate streamflow from 1200 to 2012.

With all this information, the researchers created their own reconstruction model that captured historical droughts driven by monsoon failures and connected low river levels to periods of drought-induced famine. Their findings revealed an increased frequency in synchronous drought between 1850 and 2014 compared with preindustrial centuries—an increase they surmise was likely caused by the warming climate. The researchers also suggest that future synchronous droughts may threaten water security throughout India. (AGU Advances, https://doi.org/10.1029/2025AV001850, 2025)

—Rebecca Owen (@beccapox.bsky.social), Science Writer

Citation: Owen, R. (2025), Droughts sync up as the climate changes, Eos, 106, https://doi.org/10.1029/2025EO250324. Published on 18 September 2025. Text © 2025. AGU. CC BY-NC-ND 3.0
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In recent years, the North American beaver (Castor canadensis) has been increasingly recognized as a valuable on-site engineer to help communities meet water management goals. Beavers are famously “eager” to build dams, which slow the flow of streams and allow wetland areas to grow.

Until now, however, land managers didn’t have a way to estimate how much water beaver reintroduction could actually bring to a habitat. Not every beaver dam results in a sprawling ponded complex; sometimes they result in smaller areas with less water retention than meets the needs of the community.

In a study published last month in Communications Earth and Environment, researchers from Stanford University and the University of Minnesota were able to link the amount of surface water in beaver ponds across the western United States to the features in those landscapes that make beaver ponds bigger.

Big, Beautiful…Beaver Ponds

Oftentimes, beavers will chain together multiple dams and ponds to form beaver pond complexes. The complexes increase an area’s water retention, cool water temperatures, and provide natural firebreaks. These wetland habitats also give the semiaquatic rodents ample room to roam and allow other species (such as amphibians, fish, and aquatic insects) to flourish.

Beaver pond complexes like the one in Happy Jack Recreation Area create habitat for wetland creatures big and small, like this (very large) moose. Credit: Emily Fairfax

“Our models highlight the landscape settings where ponds grow largest, helping target nature-based solutions under climate stress.”

The advantages of beaver pond complexes aren’t going unnoticed—the reintroduction of beavers to the North American landscape is an increasingly popular strategy for land managers looking to naturally improve a waterway.

“Managers need to know where beaver activity—or beaver-like restoration—will store the most water and maximize the environmental benefits, such as providing cooling and enhancing habitat quality” said Luwen Wan, a postdoctoral scholar at Stanford and the new study’s lead author. “Our models highlight the landscape settings where ponds grow largest, helping target nature-based solutions under climate stress.”

While improving water retention is a goal of many watershed management projects, especially in the increasingly drought-prone western United States, the researchers also emphasized that creating the largest possible ponds might not be the right solution for every area.

“It’s worth thinking about what we are actually asking of these beavers, and is that reasonable?”

“Bigger ponds are not always better,” said Emily Fairfax, coauthor on the study and assistant professor at the University of Minnesota. Fairfax explained that larger ponds are great for when the goal of the project involves water retention, but smaller ponds could be a better fit for a project in which the goals are pollution removal or increasing biodiversity. “It’s worth thinking about what we are actually asking of these beavers, and is that reasonable?”

How to Design a Dream Stream

Speaking on the main findings of the study, Wan said that she and her colleagues “found a clear link between the total length of beaver dams and the size of the ponds they create.” Additionally, they observed that the biggest ponds were found “where dams are longer, stream power is lower to moderate, and woody vegetation is of moderate [6–23 feet, or 2–7 meters] height.”

Included in the study were 87 beaver pond complexes across the western United States, encompassing almost 2,000 dams. Using high-resolution aerial imagery from the National Agriculture Imagery Program (NAIP), the team was able to connect the observed ponded area to different landscape measurements like soil characteristics, stream slope, vegetation metrics, and more.

The researchers chose NAIP imagery for its high spatial resolution and ability to cover large areas (visiting every beaver pond in the field would take too much time). Wan noted that while NAIP aerial imagery was the right fit for this project, it isn’t perfectly beaver proof. The imagery is updated every 2–3 years during the growing season, which may introduce some errors, like missing ponds even when dams have already been constructed.

Using remote sensing to predict where beaver reintroduction would be a successful match to the needs of a watershed isn’t a new idea. One frequently used model mentioned in the study is the Beaver Restoration Assessment Tool (BRAT). BRAT allows researchers to identify how many dams a given stream would likely be able to host. “That’s really important information to have,” said Fairfax, “but that doesn’t tell us how big the dams are, or how much water they could be storing.”

When Beavers Aren’t Best

Findings from this study are also helpful when selecting sites for beaver dam analogs (BDAs). These human-made structures are alternatives to beaver reintroduction that mimic beaver dams to achieve the same ecosystem benefits the beavers would bring. They are often the right tool when a waterway is too degraded to host a beaver population.

BDAs raise water levels and allow the preferred foods of beavers (such as willows and alders) to take root, giving “a little push” to the process of reestablishing a beaver population, explained fluvial geomorphologist and associate professor Lina Polvi Sjöberg from Umeå University in Sweden. Polvi was not involved in the new study.

Fairfax added that BDAs are a useful tool but are not equivalent to actual beaver dams. With beaver dams, a living animal is always present, so the land managers can count on the “maintenance staff on-site” to constantly update and monitor the waterway.

The Beavers Are Back in Town

North American beaver populations are still on the rebound from a long history of trapping and habitat loss that came with European colonization of the continent. “We are at maybe 10% of the historic population, and we actually don’t know if it’s still growing,” Fairfax said. Modern threats to beaver populations include highways and man-made dams, she added, which prevent beavers from freely moving back to places they once were.

Not everyone is quick to welcome North America’s largest rodent back to their neighborhood with open arms. Though public perceptions of beavers are shifting from pest to watershed management partner, the potential for contention still remains. Beavers occasionally build their dams in less-than-ideal locations, a situation that can result in flooded private properties and damaged infrastructure. The study notes that human influence (like trapping and land use conflicts) is a factor that land managers must consider but is not captured in statistical models.

Beavers Worldwide

The researchers found what makes beaver dams bigger in the western United States, but scientists say it will be important to replicate this study in different regions of North America, especially as beaver habitat expands northward as a result of climate warming.

“North American beavers are all one species, Castor canadensis. A beaver in Arizona is the same species as a beaver in Alaska. They all have the same instincts,” said Fairfax, “but beavers also do learn and adapt to their environments pretty strongly.”

She added that beavers will use the materials available to them, such as a colony in Yukon, Canada, that has been observed using rocks as dam-building material. “Whenever we build a model that describes what beavers are doing, there is a chance that it’s going to have a strong geospatial component to it,” Fairfax said.

Polvi agreed, stating that she hadn’t seen many studies using remote sensing methods to estimate the suitability of a stream for beaver reintroduction outside of the western United States. Putting things into a wider perspective, she added that some defining features of the American West, like the semiarid climate and large expanses of undeveloped public land, aren’t applicable to other regions of the world.

In an email, Wan said the next steps from this study include further exploring beavers’ ponded complexes across larger areas and “quantifying the ecosystem services these ponds provide, such as enhancing drought resilience.”

—Mack Baysinger (@mack-baysinger.bsky.social), Science Writer

Citation: Baysinger, M. (2025), What makes beaver ponds bigger?, Eos, 106, https://doi.org/10.1029/2025EO250341. Published on 18 September 2025. Text © 2025. The authors. CC BY-NC-ND 3.0
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Source: Global Biogeochemical Cycles

This is an authorized translation of an Eos article. 本文是Eos文章的授权翻译。

多年来，海洋学家们一直困惑于为何算法会在南极偏远海域的卫星图像中检测到神秘的高浓度颗粒无机碳 (PIC)。在其他地区，高PIC是单细胞浮游植物大量繁殖的标志，这种浮游植物被称为颗石藻(coccolithophores)，这些植物闪亮的碳酸钙外壳会将光线反射回卫星。然而，长期以来人们一直认为这些极地水域温度过低，不适合颗石藻生长。

如今，得益于 Balch 等人的最新船载测量数据，这个谜团终于解开了。他们发现了一种名为硅藻(diatoms)的不同类型的浮游植物，当硅藻的反射性硅质外壳（或称硅藻壳，frustules）浓度极高时，其反射率可以模拟 PIC 的反射率。这种反射率可能导致卫星算法将这些遥远的南部海域错误地归类为高 PIC 区域。

同一研究团队此前的船上观测已证实，来自颗石藻的PIC是大方解石带的成因——大方解石带是一个巨大的、季节性的、反射性的水环，环绕南极洲北部较温暖的水域。然而，在更南端，南极大陆周围异常明亮的区域仍然无法解释，推测的成因包括松散的冰块、气泡或反射性的冰川“粉”（被侵蚀的岩石颗粒）被释放到海洋中。

研究人员乘坐R/V Roger Revelle号从夏威夷向南航行，进入较少被探索的水域，这里以冰山和波涛汹涌的大海而闻名。他们测量了PIC和二氧化硅的含量，确定了光合作用速率，进行了光学测量，并在显微镜下观察了微生物。这些数据表明，这些偏远地区的高反射率主要是由硅藻壳引起的。

然而，研究人员也惊讶地发现极地水域中有一些颗石藻，这表明这些浮游植物可以在比以前想象的更冷的海水中生存。

由于颗石藻和硅藻在海洋碳固定中都发挥着重要作用，因此这些发现可能对地球的碳循环具有重要意义。研究人员表示，这项研究还可以为改进卫星算法提供参考，以便更好地区分PIC和硅藻壳。(Global Biogeochemical Cycles, https://doi.org/10.1029/2024GB008457, 2025)

—科学撰稿人Sarah Stanley

This translation was made by Wiley. 本文翻译由Wiley提供。

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Editors’ Vox is a blog from AGU’s Publications Department.

Today, in Eos, American Geophysical Union (AGU) Publications recognizes a number of outstanding reviewers for their work in 2024, as selected by the editors of each journal.

Peer review is a crucial component of the scientific process and is vital for promoting clarity and accuracy in how science is communicated.

Peer review is a crucial component of the scientific process and is vital for promoting clarity and accuracy in how science is communicated. In an era with so many ways to share ideas and research, a healthy and thriving system of peer review ensures that we encourage clear communication and maintain the highest integrity in our scientific publications. At AGU, the peer review process is conducted by scientists, starting with the journal editors. It is then the peer reviewers who take time away from their own research to volunteer time and expertise to help other scientists improve their articles and to aid publication decisions. The work of these colleagues ensures that thousands of articles each year receive independent feedback as part of a robust process of consideration and evaluation for publication. We are thankful for their efforts to make our science stronger.

Discoveries and solutions in the Earth and space sciences rely on increasingly complex approaches and datasets reflected in the papers that share their results. Peer reviewers bring their substantial expertise to evaluate detailed and intricate science conducted by teams of researchers large and small. Reviewers must assess insights gleaned from studies utilizing more and new techniques, data, and simulations that increase in scale and scope each year. As a result, both the value and challenge of peer reviewing keeps growing. Science benefits when our community rises up to support the opportunities afforded by the work reported in AGU journals by providing thoughtful and insightful feedback through peer review.

The outstanding reviewers listed here have provided in-depth, valuable, and timely feedback and evaluations, often through multiple revisions, and multiple manuscripts, that have led to clearer and greatly improved final published papers. Their contributions helped raise the quality of submissions received from around the world, delivering valuable feedback that makes for better scientific discourse.

Many Reviewers: A Key Part of AGU Journals

While we recognize these few outstanding reviewers, we also must acknowledge the incredible service to the community by all the researchers who have conducted reviews to help ensure the quality, timeliness, and reputation of AGU journals. We also welcome new and first-time reviewers who have joined the family of community servants who act as integrity stewards and have been providing authors with valuable feedback to improve their science and communication. In 2024, AGU received over 20,000 submissions, which was a significant increase from 2023, and published 7,517 papers. Most submissions were reviewed multiple times—in all, 17,947 reviewers completed 44,656 reviews in 2024.

The past several years continued to be a rollercoaster for researchers, editors, and peer reviewers. The challenges of maintaining the peer review system remain at an all-time high. Volunteer reviewers in Europe and the United States receive more invitations than they can accept, while research output in China is now the highest of any country. AGU journals continue to make progress in balancing the efforts of colleagues serving our community via conducting peer reviews even as they often struggle to invite a proportional number of reviewers across the globe. Likewise, early career researchers observe some of their more senior colleagues being overburdened by invitations and wonder why they receive so few invitations themselves. AGU is committed to building further entrance points to peer reviewing including its co-reviewing program and peer reviewing programs in individual journals.

Reviewers play a central role in the rapid feedback and publishing of new science that is at the heart of advancing the Earth and space sciences.

Amidst these challenges, each AGU journal worked to maintain low time frames from submission to first decision and publication, and consistently maintained industry-leading standards. Reviewers play a central role in the rapid feedback and publishing of new science that is at the heart of advancing the Earth and space sciences.

Editorials in each journal express our appreciation along with reviewer recognition lists. Our thanks are a small acknowledgment of the large service that reviewers bear in improving our science and its role in society.

Additional Thanks

In addition, we are working to highlight the valuable role of reviewers through events at AGU’s Annual Meeting and other meetings.

We will continue to work with the Open Researcher and Contributor ID (ORCID) network to provide official recognition of reviewers’ efforts, so that reviewers receive formal credit there. As of 10 July 2025, we have over 116,000 ORCIDs up from 100,000 ORCIDs one year ago.

Getting Your Feedback

We value your feedback, including ideas about how we can recognize your efforts even more, improve your experience, and increase your input on the science. Feel free to send your comments to publications@agu.org. We look forward to hearing from you!

Once again: Thanks to our Outstanding Reviewers of 2024!

—Matt Giampoala (mgiampoala@agu.org, 0000-0002-0208-2738), Vice President, Publications, American Geophysical Union; and Steven A. Hauck II (0000-0001-8245-146X), Chair, AGU Publications Committee

Citation: Giampoala, M., and S. A. Hauck II (2025), In appreciation of AGU’s outstanding reviewers of 2024, Eos, 106, https://doi.org/10.1029/2025EO255029. Published on 18 September 2025. This article does not represent the opinion of AGU, Eos, or any of its affiliates. It is solely the opinion of the author(s). Text © 2025. The authors. CC BY-NC-ND 3.0
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Editors’ Highlights are summaries of recent papers by AGU’s journal editors. Source: Journal of Geophysical Research: Planets

In four years, NASA’s Psyche mission will arrive at asteroid 16 Psyche, a mysterious metallic-type (or M-type) asteroid that will be the first of its kind to be visited by a space mission. Observations of 16 Psyche’s surface suggest that it is highly metal-rich, but the bulk density of the asteroid is inconsistent with being totally made of metal. There are several hypotheses for Psyche’s origin and metallic spectra, including ferrovolcanism, which hypothesizes that metallic melts are squeezed out of the crystallizing core of the asteroid and erupt as lava flows on the surface.

The model adopts a primitive meteorite bulk composition and determines the composition and density of different internal layers of the asteroid. The metal core crystallizes from the outside moving inward (solid Fe+FeNi layer). The subsequent build-up of pressure in the liquid Fe-S layer may be high enough to allow it to erupt outward to the surface. Credit: Jorritsma and van Westrenen [2025], Figure 3

Jorritsma and van Westrenen [2025]  are the first scientists to look at whether ferrovolcanism is actually possible given what we know of the meteoritic precursors for Psyche’s composition. By calculating core sizes, compositions, and densities for different meteorite types the scientists calculate buoyancy forces and excess pressures to determine if the metallic liquid would be mobile enough to produce ferrovolcanism.

They found that some meteoritic compositions could produce ferrovolcanism while others could not. If NASA’s Psyche mission finds evidence of ferrovolcanism on the asteroid’s surface, these models can help constrain its early history and composition.

Citation: Jorritsma, J. J., & van Westrenen, W. (2025). Constraints on the feasibility of ferrovolcanism on asteroid 16 Psyche. Journal of Geophysical Research: Planets, 130, e2024JE008811. https://doi.org/10.1029/2024JE008811

—Laura Schaefer, Associate Editor, JGR: Planets

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Planet satellite imagery has started to reveal the events that killed 70 people at in northern India. It clearly indicates that intense rainfall triggered landslides that transitioned into channelised debris flows.

On 5 August 2025, a series of terrifying landslides struck Dharali in Uttarkashi, Uttarakhand, northern India. I blogged about this at the time – the Wikipedia page for the disaster indicates that about 70 people were killed.

In the aftermath of the disaster, there was some very strange speculation about the cause. For example, the Times of India quotes an expert from the India Meteorological Department as follows:

“Only very light to light rain was observed in the affected area over 24 hours. The highest rainfall recorded anywhere in Uttarkashi was merely 27mm at the district headquarters.”

They quote another scientist as follows:

“This volume is insufficient to trigger floods of such severity, suggesting a powerful event such as a glacier burst or a GLOF.”

They also quote a senior geologist as follows:

“Such disasters occur when water accumulates at higher elevations and discharges suddenly … Heavy rainfall alone can’t cause such a disaster.”

This is of course a nonsense. Intense rainfall is highly spatially variable, especially in high mountains. Take a look at this “Black Rainfall” event in Hong Kong (which was not in a high mountain area, where the events are even more extreme, but Hong Kong has a fantastic rain gauge network):-

Hong Kong Observatory data showing the distribution of precipitation in a “Black rainfall” event in 2020. Credit: Hong Kong Observatory

The western and southern parts of Lantau island received less than 40 mm of rainfall that day, whilst the area around Sha Tin received over 400 mm. The distance between the boundary of >400 mm and <40 mm is a few kilometres.

Cloudburst precipitation is incredibly spatially variable, so it is not the case that a failure to record heavy rainfall on a sparse rain gauge network means that such events did not occur. And, as I have shown on numerous occasions on this blog, intense rainfall most certainly can, and does, trigger catastrophic debris flows.

However, there was a stronger piece of evidence that suggests that this event was not a glacier burst or a GLOF. On 5 August 2025, the debris flows occurred in two separate, but adjacent catchments, one at Dharali but another at Harshil, about 500 m to the west. These two catchments are not connected, but they are separated by a ridge. This would suggest a common trigger – in the absence of an earthquake, a localised rainfall event is highly likely (especially in the peak of the monsoon).

Of course, to be sure we need either fieldwork or satellite imagery. In the rainy season, this is really hard to achieve but as the monsoon withdraws this becomes possible. And sure enough, on 11 September 2025, Planet captured a fabulous satellite image that starts to reveal the story.

So let’s start with Harshil – the picture here is straightforward. The slider below shows Harshil and the lower part of the catchment using Planet imagery draped onto the Google Earth DEM. Note that the change in the topography is not captured in the DEM.

A comparison of Harshil before and after the 5 August 2025 Dharali disaster. Images by Planet, using the Google Earth DEM.

The path of the debris flow is clear, and upstream there is a very obvious large landslide. Thus, the most likely cause of the Harshil debris flow is that slope failure.

The image below shows the landslide itself, but again note that the topography in the DEM has not updated, so the morphology is distorted. But this is clearly a large rock slope failure.

I will caveat to say that at this stage we cannot definitively say that this landslide occurred on 5 August 2025, but Occam’s razor implies that this is the cause.

The landslide upstream from Harshil after the 5 August 2025 Dharali disaster. Image copyright Planet, used with permission. Image dated 11 September 2025.

This slope failure has released a huge amount of sediment into the catchment. This will cause problems for Harshil in the future.

So now let’s turn to Dharali itself. This is more complex. We have to go high up into the catchment above the village to see what’s happened. The slider below shows before and after Planet images of the upper part of the catchment above Dharali:-

Planet images showing the upper part of the catchment above Dharali before and after the 5 August 2025 disaster. Images by Planet using the Google Earth DEM.

There has been substantial change on both sides of the catchment. Let’s start with the west (the right side of the image above as the image is from the south looking towards the north):-

The west side of the upper part of the catchment above Dharali after the 5 August 2025 disaster. Image copyright Planet, used with permission. Image copyright Planet, used with permission. Image dated 11 September 2025.

The juxtaposition of the sediments lower down the valley suggests to me that this was the cause of the first (most catastrophic) debris flow at Dharali. The image strongly indicates that this was a channelised debris flow initiated by a landslide in glacial sediments in the upper part of the catchment. There was a huge amount of entrainment of channel sediments downstream. Note that there is a pre-existing, smaller, landslide at this site.

Thus, the major debris flow at Dharali was probably initiated by a shallow landslide that transitioned into a channelised debris flow.

Events on the east side of the catchment are much less clear. I suspect that the processes here generated at least some of the smaller debris flows that struck Dharali after the first event. This is the Planet image for this side of the valley:-

The east side of the upper part of the catchment above Dharali after the 5 August 2025 disaster. Image copyright Planet, used with permission. Image copyright Planet, used with permission. Image dated 11 September 2025.

The changes to the fan in the centre of the image are notable, but what caused this? I am not entirely sure. A closer comparison of the glacial sediment above this fan looks like this:-

Planet images showing the upper part of the catchment above Dharali before and after the 5 August 2025 disaster. Images by Planet using the Google Earth DEM.

In the foreground is a trough that has suffered extensive erosion. But there is also major change in the slopes above that trough. I have a suspicion that the feature that I have highlighted below might be quite significant:-

The upper eastern part of the catchment above Dharali before the 5 August 2025 disaster. Image copyright Planet, used with permission. Image dated 11 September 2025.

It appears to me that a landslide has occurred on this area of glacial sediment. Did this generate one or more channelised debris flows? There are other changes too – so maybe there were repeated shallow failures that generated the smaller debris flows observed at Dharali?

In conclusion, we can say:

1. The Dharali disaster was caused by rainfall. There is no other credible trigger that explains simultaneous events in two separate, adjacent, catchments.
2. Given the rain gauge record, this must have been a highly localised, cloudburst event.
3. Harshil was destroyed by a debris flow that probably originated from a rock slope failure in the catchment above the village.
4. The first Dharali debris flow was probably triggered by a rainfall triggered shallow landslide in glacial deposits in the upper part of the catchment, which transitioned into a channelised debris flow.
5. The subsequent debris flows at Dharali were caused by other erosive events in these glacial tills. The origin is not entirely clear, but there is evidence of at least one further shallow landslide that may have been the origin for one or more events.

This is a very provisional analysis based on lower resolution (but still brilliant) imagery. These hypotheses need to be explored through fieldwork and/or high resolution imagery.

Finally, it is absolutely inevitable that the fans at Dharali and Harshil will suffer similar events in the future. Neither will be safe for habitation.

Reference and acknowledgement

Thanks to loyal reader Jack for really interesting and stimulating discussions about these events. And special thanks to Planet for the astonishing imagery.

Planet Team (2025). Planet Application Program Interface: In Space for Life on Earth. San Francisco, CA. https://www.planet.com/

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Astronomers have recently found that roughly a third of planet-forming disks around young Sun-like stars are tilted relative to the direction that their star spins.

“All young stars start out with a disk. But the relative orientation between the disk and the star’s spin axis, little was known about that,” explained lead researcher Lauren Biddle, a planetary scientist at the University of Texas at Austin.

This discovery, published in Nature, could help answer the long-standing question of how planets come to orbit their stars at wonky angles: Maybe they were born that way.

Skewed from the Start

There’s a universal truth that when a new star collapses out of a cloud of gas, angular momentum must be conserved. That means that as the nebulous star shrinks in size, it also rotates faster, like when a spinning ice skater draws their arms in and speeds up. The surrounding leftover gas and dust flatten out into a disk that spins in the same direction as the star, and that disk may eventually form planets that spin and orbit in that same direction.

But the universe is rarely so neat and tidy.

Of the thousands of known exoplanets, dozens of them orbit at wonky angles relative to their star’s spin axis. In our own solar system, the plane in which the eight planets orbit is tilted by about 6º from the Sun’s spin axis. Astronomers have theorized that some of these misalignments, or obliquities, result from dynamical events that take place after a planetary system has already formed: A star passes by and disturbs the orbits, or a major collision knocks a planet off course.

Some of those misalignments, however, are baked in from the start. Previous studies have attempted to observe young star systems and their planet-forming disks to see whether those disks start out tilted or aligned. But those studies were limited by the fact that not many protoplanetary disks had yet been discovered, and many of those that were known were part of binary star systems, Biddle explained. Although those studies found some tilted disks, the gravity from the binary star, rather than an intrinsic misalignment, may have been the culprit.

“If systems begin with primordially tilted orbits, then there is no need to invoke other mechanisms—many of which would destabilize neighboring planets—within those systems,” said Malena Rice, a planetary astrophysicist at Yale University in New Haven, Conn. “By understanding the range of primordial tilts and comparing that distribution with more evolved systems, we can piece together the evolutionary sequences of different classes of planetary systems.” Rice was not involved with this study.

“The one-third rate of misalignment stands independent of everything else.”

Biddle and her colleagues compiled a new sample of young star systems by combining observations of protoplanetary disks from the Atacama Large Millimeter/submillimeter Array (ALMA) and measurements of stars’ spin from the Transiting Exoplanet Survey Satellite (TESS) and retired K2 mission. Biddle explained that because ALMA, TESS, and K2 have released such large datasets, her team could curate their sample to look only at Sun-like stars that did not have any binary companions.

They found that 16 of the 49 stars in their sample (about a third) had protoplanetary disks with obliquities of at least 10°, the lower limit of what they could measure. The remaining two thirds of the systems showed no significant evidence of misalignment. This rate of high-obliquity disks is consistent with past studies but more than doubles the number of young, single, Sun-like stars for which astronomers know the degree of disk misalignment.

The 16 stars that host tilted disks did not share any obvious characteristics like mass, temperature, and size, and the disks themselves also had different sizes, masses, and structures.

“We didn’t find any correlation there,” Biddle said. “At this point, independent of other system parameters, the one-third rate of misalignment stands independent of everything else.”

Oblique Across Space and Time

Past studies have suggested that moderate disk obliquities might rise from imperfections in the nebulous cloud that formed the star system: An odd clump in the right spot might create turbulence that grows stronger as the cloud collapses, or the clump might fall onto the disk late and tip it off its axis.

“Moderate misalignments of a few tens of degrees can be produced naturally by either turbulence in the natal molecular cloud, late-stage disk accretion, or some combination of the two,” Rice said.

However, that doesn’t necessarily mean that every misaligned exoplanet, or even a third of them, started out that way.

“It would be great to take a crack at mapping stellar obliquities across space and time.”

“A misalignment between a planet’s orbital plane and its host star’s spin axis can originate in two broad phases: during the star and planet formation stage…[and] later, during the system’s main sequence lifetime,” explained Simon Albrecht, an astronomer at Aarhus University in Denmark who was not involved with this research. “If we can determine the fraction of systems that are already misaligned right after birth, that helps us distinguish between these two broad possibilities.”

Determining how much of a system’s tilt comes early or late and whether that tilt changes over a planetary system’s lifetime will require observing a lot more misaligned planetary systems at all stages of evolution, Biddle said. She added that the upcoming data release from the now-retired Gaia mission will be key to answering both of those questions.

“It would be great to take a crack at mapping stellar obliquities across space and time,” Biddle said. “Being able to fill in that time parameter space will help quantify how important dynamics is for generating that final [obliquity] distribution that we observe in planetary systems.”

—Kimberly M. S. Cartier (@astrokimcartier.bsky.social), Staff Writer

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Citation: Cartier, K. M. S. (2025), Tilted planet system? Maybe it was born that way, Eos, 106, https://doi.org/10.1029/2025EO250338. Published on 17 September 2025. Text © 2025. AGU. CC BY-NC-ND 3.0
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Editors’ Highlights are summaries of recent papers by AGU’s journal editors. Source: AGU Advances

To help project Earth’s future climate, it is critical to understand how the capacity of ecosystems to take up and store carbon is changing as atmospheric carbon dioxide levels rise and climate change intensifies.

Bilir et al. [2025] integrate satellite data with a model of terrestrial carbon cycling to parse regionally-specific influences of CO2 and climate on carbon storage in living and dead plant material, and the associated residence time of carbon in those pools.

For the specified regions, changes in total carbon storage (left Y axis, solid bars) and percent change in mean residence time of carbon (right Y axis, hatched bars) that can be attributed to atmospheric CO2 (top panel), climate trends (middle panel), and the combined, interacting effects of CO2 and climate (bottom panel). Credit: Bilir et al. [2025], Figure 6

Their work helps untangle the mechanisms driving what they and others have observed: that CO2 increases carbon storage more than climate effects decrease it. They find greater carbon storage in living plants globally and a shift in dead carbon storage from mid- and high latitudes to the tropics. They also demonstrate a reduction in mean carbon residence times across all latitudes. The shift in carbon storage from dead to live pools underscores the sensitivity of terrestrially-mediated carbon cycling and residence times to living plant carbon uptake and storage potentials.

These efforts help us understand, at a global scale, how rising atmospheric CO2 and climate change interact to prompt a latitudinally-specific reorganization of our planet’s terrestrial carbon cycling, and thus its climate.

Citation: Bilir, T. E., Bloom, A. A., Konings, A. G., Liu, J., Parazoo, N. C., Quetin, G. R., et al. (2025). Satellite-constrained reanalysis reveals CO2 versus climate process compensation across the global land carbon sink. AGU Advances, 6, e2025AV001689. https://doi.org/10.1029/2025AV001689

—Sharon Billings, Editor, AGU Advances

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Climate change caused 16,469 deaths in European cities this summer, new research estimates.

This summer was the fourth hottest in European history, and its effects on the continent’s population have been widely reported. Spain experienced its most intense heat wave in history in August 2025. Türkiye saw its highest recorded temperature ever (50.5°C, or 122.9°F). Finland saw an “unprecedented” three straight weeks of 30°C heat.

A new, rapid-analysis study by researchers at Imperial College London (ICL) and the London School of Hygiene & Tropical Medicine estimated that 24,400 people across 854 European cities and urban centers died from heat-related causes between June and August 2025. Using climate models and a comparison of this figure with how many heat-related deaths would have occurred in a 1.3°C cooler world, the researchers estimated that climate change was responsible for 68% of these deaths.

“These numbers represent real people who have lost their lives in the last months due to extreme heat.”

“In other words, it could have tripled the death toll,” said Garyfallos Konstantinoudis, a biostatistician at ICL’s Grantham Institute – Climate Change and the Environment.

Though the planet has warmed about 1.3°C overall since preindustrial times, Europe is warming more quickly than the rest of the planet, meaning that temperatures on the continent this summer were about 1.5°C to 2.9°C warmer than they would have been without anthropogenic warming.

In a Tuesday press conference, the researchers explained that their estimate of 16,649 climate-related deaths is likely conservative, in part because climate models are known to underestimate warming in Europe. In addition, their estimate includes only deaths in urban centers with populations above 50,000 people—areas that represent only about 30% of Europe’s population. They focused on these urban areas because these locations had greater data availability, but that means the estimate is just a snapshot.

“These numbers represent real people who have lost their lives in the last months due to extreme heat,” said Friederike Otto, a climatologist at ICL’s Centre for Environmental Policy. “Many of these would not have died if it wasn’t for climate change. And if we continue on the path that we are on now, continue burning fossil fuels, these deaths will only increase.”

The Hidden Costs of Heat

The study also notes that northern Europe experienced a higher proportion of heat-related deaths than southern Europe, despite southern Europe enduring higher heat (some cities in the region have warmed by up to 3.6°C) and more excess mortality overall. The reason is that prior to climate change, heat in northern Europe rarely reached levels that affected human health at all. Now, explained Konstantinoudis, “almost all of the heat-related deaths in northern Europe…are due to climate change.”

“Reducing fossil fuel use is one of the most important public health interventions of our time.”

Courtney Howard, vice-chair of the Global Climate and Health Alliance and an emergency physician in Canada’s Yellowknives Dene Territory, who was not involved in the study, noted that extreme heat can raise the risk of deadly heart attacks and strokes because high heat causes the heart to work harder. It can also fatally worsen respiratory conditions such as asthma because ozone pollution tends to increase during extreme heat events. Thus, many of the deaths that occur during heat waves are not necessarily recorded as heat deaths.

“The result is that heat numbers capture only a small fraction of the real story at the bedside,” she said. “Experts do not believe that we can adapt health systems adequately to cope with the temperatures that we are currently facing. That’s why reducing fossil fuel use is one of the most important public health interventions of our time.”

To estimate heat deaths, researchers turned to an existing dataset that showed relationships between temperature and mortality across the 854 urban areas used in the study. They then estimated the number of daily deaths during the heat wave using historical Eurostat data and information on which days exceeded minimum mortality temperature.

It’s Not Just Europe Click image for larger version. Credit: Imperial Grantham Institute

Among the countries included in the study, the Baltic nations of Estonia, Latvia, and Lithuania were the only three that did not experience hotter-than-usual summers.

Rome, Athens, and Bucharest saw the highest heat-related death rates per capita among European capital cities, the study found. In general, cities are hotter than surrounding areas because of the urban heat island effect, in which concrete surfaces trap heat and raise city temperatures.

Chris Callahan, a climate scientist at Indiana University Bloomington who was not involved in the study, said that though the study is not peer reviewed, its methods appear to be “standard and based on extensive peer-reviewed research.”

The researchers noted several factors their study did not consider, including cities’ efforts to adapt to climate change and all adverse health effects of heat. It also did not capture changes to baseline populations that occurred post-COVID-19, which might have led to higher numbers for some cities.

“The findings in this study are stark and concerning, as they illustrate that climate change is already the dominant influence on heat-related mortality in Europe,” Callahan told Eos in an email.

“We are warming the world through our fossil fuel emissions and other activities and that…is causing people to die.”

Europe faces particularly high risks related to climate change, he added, both because temperatures are rising more quickly in western Europe than in other parts of the world and because Europe’s aging population is highly vulnerable to heat. In fact, this study found that people over 64 made up 85% of the climate-related deaths in European cities this summer.

However, the study authors noted that the growing toll warming is taking on human health is not unique to Europe.

“The specifics will vary wherever you’re looking in the world, but the basic point of these studies will always be the same: that we are warming the world through our fossil fuel emissions and other activities and that this is causing people to die,” said Clair Barnes, a statistician at ICL’s Centre for Environmental Policy.

—Emily Gardner (@emfurd.bsky.social), Associate Editor

Citation: Gardner, E. (2025), Climate change may have killed 16,469 people in Europe this summer, Eos, 106, https://doi.org/10.1029/2025EO250348. Published on 17 September 2025. Text © 2025. AGU. CC BY-NC-ND 3.0
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body {background-color: #D2D1D5;} Research & Developments is a blog for brief updates that provide context for the flurry of news regarding law and policy changes that impact science and scientists today.

Misunderstandings and disinformation abounded at a 16 September hearing of the Subcommittee on Delivering on Government Efficiency about geoengineering, which encompasses efforts to alter Earth systems for the purpose of mitigating climate change. 

Rep. Marjorie Taylor Greene (R-GA), chairwoman of the subcommittee, called for an outright ban on geoengineering and used the hearing to promote her Clear Skies Act, which would impose fines of up to $100,000 and potentially jail time for anyone conducting “weather modification” activities.

Geoengineering is an amorphous term that can refer to a range of climate intervention activities, including cloud seeding to spur precipitation, management of solar radiation to cool Earth by reflecting sunlight, and carbon capture and sequestration efforts.

“Today’s advocates of geoengineering don’t just want to address droughts or improve conditions for agriculture” Greene said. “They want to control the Earth’s climate to address the fake climate change hoax and head off global warming. That, of course, requires massive interventions.”

In addition to asserting that climate change is a hoax, Greene implied that climate interventions could remove enough carbon dioxide from the atmosphere to harm plant life. In questioning, Rep. Brian Jack (R-GA) repeated a dubious claim that the release of dry ice into a hurricane in 1947 in an experiment called Project Cirrus caused the hurricane to turn toward Georgia. And Rep. Pat Fallon (R-TX) argued that former Vice President Al Gore’s misrepresentation regarding the melting of the north polar ice cap invalidates decades of climate science. 

One witness during the hearing was Christopher Martz, a policy analyst and meteorologist at the Committee for a Constructive Tomorrow, an environmental policy think tank that has cast doubts on climate science. Martz received an undergraduate degree in meteorology in May and runs a weather blog that questions the influence of climate change in extreme weather events. 

 
Related

•  Marjorie Taylor Green Introduces ‘Weather Modification’ Ban
•  Watch the hearing: Playing God with the Weather — A Disastrous Forecast
•  AGU’s Ethical Framework Principles for Climate Intervention Research
•  Get Involved: AGU Science Policy Action Center
 

Martz asserted that the science behind climate change is uncertain, and therefore that climate intervention is an alarmist reaction: “Warming could be mostly natural and we just don’t know,” he said. It’s not: The vast majority of scientists agree that Earth is warming and human activities are to blame.

The hearing’s only climate scientist witness, former Lawrence Livermore National Laboratory scientist Michael MacCracken, tried to combat the climate denialism in the room. He challenged the ideas that current climate intervention efforts are sufficiently powerful or scalable enough to change a major weather phenomenon, or that they are targeted to harm the public.

Despite the falsehoods raised by Greene and others at the hearing, some of their comments aligned with how many scientists view climate intervention—as a potentially risky endeavor that requires more research before it is considered viable and safe.

AGU’s own Ethical Framework Principles for Climate Intervention Research, developed with the contributions of scientists, policymakers, ethicists, government agencies, nongovernmental organizations, and potentially impacted communities, acknowledges this perspective: “Substantial research and evaluation efforts will be required to determine the effectiveness, risks, and opportunities of climate intervention,” the framework states.

At the hearing, Greene asked “who would control the dial” if scientists managed to reliably alter Earth’s climate.

Such questions are a reason to lean into Earth systems research, said Roger Pielke, Jr., a political scientist at the conservative American Enterprise Institute who spoke at the hearing. Pielke called for Congress to enact legislation to improve oversight of geoengineering and recommended that Congress ask the National Academy of Sciences to assess what scientists do and don’t know about the effects of climate intervention activities.

Rep. Melanie Stansbury (D-NM), ranking member of the subcommittee, closed the hearing with a plea to support science. “Literally all we’re trying to accomplish by climate action is to keep our planet in some sort of balance,” she said, calling the Trump administration’s firing of federal scientists and engineers, the defunding of science agencies, the firing of the EPA science panel, and the deregulation of carbon emissions “dangerous.”

Stansbury and Greene agreed on one thing: “We have one Earth,” they each said.

—Grace van Deelen (@gvd.bsky.social), Staff Writer

These updates are made possible through information from the scientific community. Do you have a story about how changes in law or policy are affecting scientists or research? Send us a tip at eos@agu.org. Text © 2025. AGU. CC BY-NC-ND 3.0
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After a tropical cyclone passes through an area, governments take stock of the damage. NOAA, for instance, lists the costs associated with damaged buildings and roads and reports any injuries or deaths attributed to the storm.

“This research supports the historically overlooked indirect health risk and burden of tropical cyclones.”

However, research suggests that storms can also have hidden, long-term consequences for human health. In a new study published in Science Advances, scientists report that cyclones, also known as hurricanes and typhoons, produce a significant uptick in hospitalizations due to cardiovascular disease for months after they subside. In addition, the potential populations at risk for such hospitalizations are growing as a result of climate change intensifying cyclones and driving them into temperate regions such as Canada and New Zealand.

“This research supports the historically overlooked indirect health risk and burden of tropical cyclones and suggests the need for extending public health interventions and disaster preparedness beyond the immediate cyclone aftermath,” said Wenzhong Huang, an environmental epidemiologist at Monash University in Australia and the lead author of the new study.

Heart Problems Spike After Storms

Previous studies have examined possible connections between cardiovascular disease and cyclones, but most have focused on a single health center and storm in the United States.

“For our study, we encompassed multiple tropical cyclone events across decades and across multiple countries and territories with diverse socioeconomic contexts,” Huang said. “We also analyzed much longer post cyclone periods.”

“I didn’t expect that the risk would persist that long.”

The researchers tracked cardiovascular disease–related hospitalizations of more than 6.5 million people across Canada, New Zealand, South Korea, Taiwan, Thailand, and Vietnam from 2000 to 2019. They identified 179 locations that experienced cyclones and documented how many days storms hit each area. The team then examined hospital records to see whether more people were admitted for heart problems after cyclones, tracking patients for up to a year after each storm.

The results revealed that hospitalizations associated with heart health jumped 13% for every additional day a location was hit by a cyclone. The biggest spike in hospitalizations didn’t occur immediately after the cyclones but, rather, came 2 months after they passed, and the increased risk of hospitalizations didn’t subside until 6 months later.

“I didn’t expect that the risk would persist that long,” Huang said.

The health burden also fell unevenly across populations. Men, people in their 20s through 50s, and those in disadvantaged communities had the highest risk. In fact, cardiovascular risks after cyclones fell during the study period in wealthier areas while rising in poorer areas. This result suggests that improved health care access and disaster preparedness have benefited only some populations, with Thailand and Vietnam seeing the most cyclone-related heart problems. In total, strokes and ischemic heart disease (in which blood vessels supplying the heart are narrowed) were the most common maladies reported.

“There is not a single disease that’s not touched upon by hurricanes.”

Naresh Kumar, an environmental health scientist at the University of Miami who studies the health effects of cyclones but was not involved in the new study, was not surprised by the findings. According to his own extensive research on hurricanes in Florida and Puerto Rico, “there is not a single disease that’s not touched upon by hurricanes,” Kumar said.

But he would have liked the authors of the new study to narrow down the mechanisms driving up cardiovascular health risk after cyclones. The possible causes are abundant. In the months following a cyclone, people increase their use of generators, which produce pollutants; eat more calorie-dense canned foods; can’t exercise or access prescription medicines as easily; and are under immense psychological stress—all of which can increase the risk of cardiovascular disease. Meanwhile, regular health care services are often disrupted, so preventative care is limited.

Understanding these mechanisms is critical because current disaster response systems vastly underestimate the health burden of tropical storms, researchers say. “We are still scratching the surface in terms of characterizing the health effects of hurricanes,” Kumar said.

Huang said untangling the most significant contributors to increased risk following a cyclone is the next phase of his research. “I want to understand and investigate the candidates underlying this risk pattern,” he said.

As part of this process, Huang also aims to identify the reasons behind the elevated risk in some populations, such as working-age men. The research could help public health officials target interventions to high-risk populations and monitor cardiovascular health in the months following cyclones.

The Worsening Exposure to Storms

Answering the question of why more people suffer from heart problems after cyclones is becoming increasingly important to policymakers as more communities come under threat. Warmer oceans are fueling more intense storms with higher wind speeds and longer durations, while rising sea levels worsen storm surge flooding that can prolong recovery.

Climate change is also pushing tropical cyclones poleward into regions that have historically experienced few severe storms, such as eastern Canada and New Zealand. “Places that historically experienced fewer cyclone events could have much higher risk,” Huang said, suggesting such regions may be inadequately equipped to respond to major storms. “We need to focus on these regions to better prepare for the growing risk.”

—Andrew Chapman (@andrewchapman.bsky.social), Science Writer

Citation: Chapman, A. (2025), Cyclones affect heart health for months after they subside, Eos, 106, https://doi.org/10.1029/2025EO250342. Published on 16 September 2025. Text © 2025. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

It’s been nearly 2 centuries since a planet was discovered in the solar system. But now scientists think they’ve uncovered evidence of a newcomer that just might usurp that honor from Neptune. Following an analysis of the orbits of bodies in the Kuiper Belt, a team has proposed that an unseen planet at least 25 times more massive than Pluto might reside there. These results were published in Monthly Notices of the Royal Astronomical Society.

The Kuiper Belt is loosely defined as a doughnut-shaped swath of space beginning just beyond the orbit of Neptune and extending to roughly 1,000 times the Earth-Sun distance. It’s home to untold numbers of icy, rocky objects, including Pluto and other so-called Kuiper Belt objects such as Arrokoth.

Everything in the Kuiper Belt can be thought of as cosmic debris, said Amir Siraj, an astrophysicist at Princeton University and lead author of the new paper. “It represents some of the leftovers from the formation of our solar system.”

And most of those leftovers are small: Pluto is the most massive known Kuiper Belt object, and it’s just 0.2% the mass of Earth.

But over the past decade, scientists have hypothesized that something substantially larger than Pluto might be lurking in the Kuiper Belt. Evidence of that unseen world—a so-called Planet Nine or Planet X—lies in the fact that six Kuiper Belt objects share curiously similar orbital parameters and are associated in physical space. A nearby, larger planet could have shepherded those worlds into alignment, researchers have proposed.

Planes, Planes, Everywhere

Siraj and his colleagues recently took a different tack to look for a massive resident of the Kuiper Belt: They analyzed a much larger sample of Kuiper Belt objects and focused on their orbital planes. One would naively expect the average orbital plane of Kuiper Belt objects to be the same as the average orbital plane of the planets in the solar system, said Siraj. But a planet-mass body in the Kuiper Belt would exert a strong enough gravitational tug on its neighboring Kuiper Belt objects to measurably alter the average orbital plane of the Kuiper Belt, at least in the vicinity of the planet. Siraj and his collaborators set out to see whether they could spot such a signal.

“Neptune has a really strong grasp on the outer solar system.”

The researchers extracted information about the orbits of more than 150 Kuiper Belt objects from the JPL Small-Body Database managed by NASA’s Jet Propulsion Laboratory in Pasadena, Calif. Of the several thousand known Kuiper Belt objects, the team honed in on that subset because those objects aren’t gravitationally influenced by Neptune. Neptune is the playground bully of the outer solar system, and the orbits of many Kuiper Belt objects are believed to be literally shoved around by gravitational interactions with the ice giant. “Neptune has a really strong grasp on the outer solar system,” said Siraj.

The team calculated the average orbital plane of their sample of Kuiper Belt objects. At distances of 50 to 80 times the Earth-Sun distance, they recovered a plane consistent with that of the inner solar system. But farther out, at distances between 80 and 200 times the Earth-Sun distance, the researchers found that their sample of Kuiper Belt objects formed a plane that was warped relative to that of the inner solar system. There was only a roughly 4% probability that that signal was spurious, they calculated.

Meet Planet Y

Siraj and his collaborators then modeled how planets of different masses at various orbital distances from the Sun would affect a simulated set of Kuiper Belt objects. “We tried all sorts of planets,” said Siraj.

By comparing those model results with the observational data, the researchers deduced that a planet 25–450 times more massive than Pluto with a semimajor axis in the range of 100–200 times the Earth-Sun distance was the most likely culprit. There’s a fair bit of uncertainty in those numbers, but the team’s results make sense, said Kat Volk, a planetary scientist at the Planetary Science Institute in Tucson, Ariz., not involved in the research. “They did a pretty good job of bracketing what kind of object could be causing this signal.”

To differentiate their putative planet from Planet X, Siraj and his colleagues suggested a new name: Planet Y. It’s important to note that these two worlds, if they even exist, aren’t one and the same, said Siraj. “Planet X refers to a distant, high-mass planet, while Planet Y denotes a closer-in, lower-mass planet.”

“This is really expected to be a game changer for research on the outer solar system.”

There’s hope that Planet Y will soon get its close-up. The Legacy Survey of Space and Time (LSST)—a 10-year survey of the night sky that will be conducted by the Vera C. Rubin Observatory in Chile beginning as soon as this fall—will be supremely good at detecting Kuiper Belt objects, said Volk, who is a member of the LSST Solar System Science Collaboration. “We’re going to be increasing the number of known objects by something like a factor of 5–10.”

It’s entirely possible that Planet Y itself could be spotted, said Volk. But even if it isn’t, simply observing so many more Kuiper Belt objects will better reveal the average orbital plane of the Kuiper Belt. That will, in turn, shed light on whether it’s necessary to invoke Planet Y at all.

Even if his team’s hypothesis is proven wrong, Siraj says he’s looking forward to the start of the LSST and its firehose of astronomical data. “This is really expected to be a game changer for research on the outer solar system.”

—Katherine Kornei (@KatherineKornei), Science Writer

Citation: Kornei, K. (2025), A survey of the Kuiper Belt hints at an unseen planet, Eos, 106, https://doi.org/10.1029/2025EO250344. Published on 16 September 2025. Text © 2025. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.