EOS

Editors’ Highlights are summaries of recent papers by AGU’s journal editors. Source: Tectonics

How do we detect past fault slip in slowly deforming regions like the Eastern Alps, where modern earthquakes are infrequent and geologic markers of seismicity are subtle or absent?

Prince et al. [2025] tackle this challenge using two innovative dating techniques: optically stimulated luminescence (OSL) and electron spin resonance (ESR). These “trapped charge” methods harness electrons that are caught in crystal defects or impurities in quartz or feldspar grains but can be released by stimuli such as light or heat. Here, the authors target quartz and feldspar in crushed fault rocks, or fault gouge. During an earthquake, work done to overcome the frictional strength of fault rocks is given off in the form of heat that may “reset” the OSL and ESR systems.

The authors compare ESR and OSL signals from fault gouges from three faults in the Eastern Alps: the Šoštanj, Periadriatic, and Lavanttal faults. They also quantify the ESR signal saturation, which gauges how close the trapped electron system is to its maximum capacity. Their results indicate that the Periadriatic and Šoštanj faults were active during the Quaternary period (the past about 2.6 million years). The Šoštanj fault shows evidence for the most recent activity, with OSL dates as young as about 30,000 years and low ESR saturation levels suggesting repeated signal resetting. In contrast, the Lavanttal fault gouge exhibits saturated ESR signals with dates ranging from about 860,000 to over 2 million years. These results imply the Lavanttal fault was seismically quiescent during the Quaternary, or the conditions of fault slip did not yield sufficient temperatures to reset the trapped charge systems.

This study spotlights the growing utility of trapped charge dating for documenting the slip histories of faults with or without historical seismicity. The analytical uncertainty of any trapped charge date (see figure above) far exceeds an individual or multiple earthquakes, and fault-slip temperatures at shallow depths can be insufficient to completely reset these systems, so it is challenging to fingerprint individual earthquakes with this approach. However, by harnessing the complementary strengths of OSL and ESR together with ESR saturation levels, the authors are able to reconstruct a fuller picture of the timing and distribution of shallow fault slip, which is critical for understanding regional tectonics and assessing seismic hazard.

Citation: Prince, E., Tsukamoto, S., Grützner, C., Bülhoff, M., & Ustaszewski, K. (2025).  Deciphering Pleistocene fault activity in the Eastern Alps: Dating fault gouges with electron spin resonance and optically stimulated luminescence. Tectonics, 44, e2024TC008662. https://doi.org/10.1029/2024TC008662

—Alexis Ault, Associate Editor, Tectonics

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.

At least 43 people were killed in devastating landslides and debris flows in northern China. Planet Labs images provide an insight into this disaster.

It is extremely challenging to keep up with the landslides occurring around the world at the moment. There has been a lot of attention paid to the remarkable rock slope failure and tsunami in Alaska. I feel that others are better placed to write about that (although I will probably continue to highlight updates via my BlueSky account), but if you get a chance please take a look at the images on the Alaska News Source website.

There have also been a devastating set of debris flows in northern Pakistan and parts of India and Nepal. At this stage, it is a little unclear to me as to the full extent of these events (especially in Pakistan) – I am likely to return to this theme.

Often the best way to understand an event is to piece together the news reports with satellite images when they become available. And so, let’s take a look at reported “floods” or “flash floods” (actually landslides and channelised debris flows) that occurred in Yuzhong County in Gansu Province in China on 7 August 2025. The BBC has a good report of the aftermath, whilst Al Jazeera reports 10 dead and 33 missing from this event. We must take reports of losses in China with a large pinch of salt.

The location of the source of this event is [35.71498, 104.02436]. So here is a Planet Labs image, dated 30 July 2025, showing the area affected. The marker is at the location highlighted above:-

Planet Labs image of the source of the 7 August 2025 landslides and debris flows in Yuzhong County, Gansu Province. Image copyright Planet Labs, used with permission. Image dated 30 July 2025.

And here is the same location after the event:-

Planet Labs image of the aftermath of the 7 August 2025 landslides and debris flows in Yuzhong County, Gansu Province. Image copyright Planet Labs, used with permission. Image dated 13 August 2025.

And here is a slider to allow you to compare the images:-

Images copyright Planet Labs.

This is a closer look at this area of intense landslides:-

Planet Labs image of the aftermath of the 7 August 2025 landslides and debris flows in Yuzhong County, Gansu Province. Image copyright Planet Labs, used with permission. Image dated 13 August 2025.

What we see here is literally hundreds of shallow failures that will have occurred almost simultaneously, and then combined to form devastating channelised debris flows. There are many failures on the slopes to the southwest, but the greatest concentration is to the northwest is an area that is densely vegetated.

This is indicative of extremely high rainfall intensities, but this storm was highly localised. The area of intense landslides is only about 9 km x 5 km.

The downstream impacts were terrible. These are the settlements immediately to the east of the landslides:-

Planet Labs image of the downstream area affected by the 7 August 2025 landslides and debris flows in Yuzhong County, Gansu Province. Image copyright Planet Labs, used with permission. Image dated 30 July 2025.

And here is the same area after the landslides:-

Planet Labs image of the downstream area affected by the 7 August 2025 landslides and debris flows in Yuzhong County, Gansu Province. Image copyright Planet Labs, used with permission. Image dated 13 August 2025.

And again, here is a slider to allow the images to be compared:-

Images copyright Planet Labs.

There is a large number of destroyed buildings in this imagery. The devastation extended for a considerable distance.

Reference

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

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Regions known as large low shear velocity provinces—more memorably known as “big lower-mantle basal structures,” or BLOBs—have long been known to seismologists because seismic waves generated by earthquakes slow down when they pass through them.

One BLOB is under Africa, and the other sits below the Pacific Ocean. They are thousands of kilometers wide and may be more than a thousand kilometers high, containing up to 8% of Earth’s total volume.

The origin of the BLOBs is not certain, nor is it clear what they are made of. Many researchers think the BLOBs formed from subducting oceanic crust at ancient plate boundaries, while another hypothesis suggests they are remnants of the asteroid impact that threw up the material that became the Moon.

BLOBs are hotter than the surrounding mantle and perhaps compositionally distinct. While some research predicts they are denser than the mantle rock that houses them, other models have found the opposite.

Plume Factories

In the early 2000s, a group of scientists led by Trond Torsvik of the University of Oslo suspected a link between the BLOBs and volcanic activity at Earth’s surface. To test this theory, they mapped the location of large igneous provinces (LIPs) and kimberlites—diamond-bearing volcanic rocks that originate deep in Earth’s interior. The researchers then rewound the clock on these emplacements, restoring them to their position on Earth’s surface when the eruptions occurred.

The results, published in 2006, revealed that most of the eruptions occurred at the edges of one of the BLOBs. These findings supported the idea that large mantle plumes at BLOB edges hurl heat energy toward the surface and create LIPs. Activity at LIPs can trigger supervolcanoes, rip supercontinents apart, and release vast amounts of greenhouse gases. LIPs have even been implicated in some of Earth’s major mass extinctions.

The neat fit between eruptions and the position of the BLOBs, researchers claimed, showed that the BLOBs were immobile; tectonic plates moved relative to them, but the BLOBS themselves stayed where they were.

Not So Fast…

Nicolas Flament, a geophysicist and geodynamicist with the University of Wollongong (UOW) in Australia, said the idea of fixed BLOBs was initially attractive to researchers because it promised to fill a knowledge gap in the paleomagnetic history of Earth.

Geologists trace the movement of tectonic plates using paleomagnetic evidence, written by Earth’s magnetic field on volcanic rocks as they cool and solidify. These data can reveal the latitudinal position of an eruption on Earth’s surface, but they cannot reveal anything about longitude.

“Everything moves.”

If BLOBs are fixed in one spot, Flament said, ancient eruptions could be linked to the edges of the BLOBs, providing a much-needed reference for paleolongitude.

As a geodynamicist, however, Flament inhabits a world where, he said, “everything moves.” The concept of fixed BLOBs didn’t sit well with him. In 2022, he and some colleagues ran models that rewound Earth’s clock back a billion years. These models showed that the position of volcanic materials at the surface could be explained just as well if the BLOBs moved.

Flament and his team contend that subducting slabs disrupt the BLOBs, and they regularly break apart and remeld just like continents do at the surface. But by Flament’s own admission, there is a weakness in these findings. Like the Torsvik-led research, it “assumed that there was a link between the BLOBs and the eruptions…We didn’t actually check” to confirm that the link was there.

Bridging the Gap

Now a team led by UOW Ph.D. student Annalise Cucchiaro that includes Flament has shown through statistical modeling that large volcanic eruptions are, indeed, connected to the BLOBs. The team mapped volcanic deposits against billion-year reconstructions of mantle movement. The research was published in Communications Earth and Environment.

The scientists found a significant link between volcanic deposits and the mantle plumes that models predicted, “essentially filling that gap,” Flament said.

The researchers found no significant relationship between mantle paths and the BLOB edges, however—mantle plumes could originate from anywhere on the BLOB, not just the edge. As plumes rise through Earth’s interior, they encounter “mantle wind”—lateral movement of semisolid rock that may cause the plumes to tilt by as much as 5° from vertical. This tilting, the research showed, could account for many of the volcanic eruptions that were not directly over a BLOB.

The research also suggested that the BLOBs are slightly denser and less viscous than the surrounding mantle. Rather than being completely static, the BLOBs likely move around at a rate of about 1 centimeter per year.

Qian Yuan, a geophysicist with Texas A&M University who was not involved in the study, called the findings “very reasonable.” Yuan was the author of the asteroid origin theory of BLOB formation.

“The subducting slab is the strongest driving force of the manual convection,” he said, “so in all our models, we show the BLOBs will move around.”

Big Bottoms

Fred Richards, a geodynamicist at Imperial College London who was not involved in the study, has researched BLOBs extensively, looking for a model that accommodates everything known about them from seismological and geophysical data.

The UOW research, he said, adds to a growing body of evidence that the lower parts of the BLOBs are dense, but not too dense to prevent them from moving around. Linking a dense, viscous base to the eruption record, he said, is “something that hasn’t been clearly shown before.”

—Bill Morris, Science Writer

Citation: Morris, B. (2025), Blame it on the BLOBs, Eos, 106, https://doi.org/10.1029/2025EO250302. Published on 15 August 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.

Source: Geophysical Research Letters

Off the southern coast of Chile, three tectonic plates meet at a point known as the Chile Triple Junction. Two are oceanic plates, the Nazca and the Antarctic, which are separating in an active spreading center, creating a mid-ocean ridge between them. At the same time, both plates—spreading ridge included—are sliding into the mantle beneath a third plate, the South American. The Chile Triple Junction is the only place on Earth where an active spreading center is subducting under a continental plate.

Just to the east of the triple junction, beneath South America’s Patagonia region, a gap known as a slab window exists between the subducting oceanic plates. Caused by the subduction of the spreading center, the window exposes the overriding South American plate to hot mantle material from below.

Knowing the size and geometry of this opening is key for parsing out the area’s complex geology. However, limited offshore observations have left researchers unsure of where the slab window begins.

Recently, a new array of seismic stations deployed on the ocean floor off of Chile’s coast has boosted opportunities for observation. According to Azúa et al., the new seismic data help to pinpoint the beginning of the Patagonian slab window to just south of the Chile Triple Junction.

The seismic data captured shallow tectonic tremors, a type of “slow earthquake” that releases energy more gradually than conventional quakes—often over the course of several days. Slow earthquakes are increasingly being studied to enhance understanding of plate boundaries.

Using nearly 2 years’ worth of the new ocean bottom seismic data, the research team detected about 500 shallow tremors near the Chile Triple Junction. When they compared the locations of these tremors with the locations of previously detected conventional earthquakes, they noticed a distinct gap between where the two types of events occur.

The researchers interpret the gap in seismic activity as evidence of the youngest part of the Patagonian slab window, formed within the past 300,000 years.

Although further research will be needed to confirm and build on these findings, this work represents the first direct evidence of the offshore edge of this hole between the two subducting plates. (Geophysical Research Letters, https://doi.org/10.1029/2025GL115019, 2025)

—Sarah Stanley, Science Writer

Citation: Stanley, S. (2025), Finding the gap: Seismology offers slab window insights, Eos, 106, https://doi.org/10.1029/2025EO250299. Published on [DAY MONTH] 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.

Parts of Greater New Orleans are sinking by millimeters per year, increasing their vulnerability to floods and storm surges.

Flood protection infrastructure put in place in the months and years following Hurricane Katrina in 2005 could lose effectiveness more quickly than expected.

Though most of the city is stable, areas near the Louis Armstrong New Orleans International Airport, sections of flood protection walls, and certain industrial sites and wetlands are losing elevation, researchers reported in Science Advances earlier this summer. The rate and scale of these losses vary because rates of subsidence are affected by multiple factors, including groundwater pumping, wetland drainage, construction and urban development, and natural soil compaction.

Coupled with rising sea levels, the rapid subsidence could mean that without regular upgrades, flood protection infrastructure put in place in the months and years following Hurricane Katrina in 2005 could lose effectiveness more quickly than expected.

Spotting Subsidence from Above

As part of the new research, remote sensing expert Simone Fiaschi and his colleagues used interferometric synthetic aperture radar, or InSAR, to map subsidence across the city in 2002–2007 and 2016–2020. InSAR measures the distance between a satellite orbiting Earth and the planet’s surface. When averaged over measurements taken at different times, the satellite data can be used to detect millimeter-scale changes in elevation.

Knowing where and how quickly subsidence is occurring can clue scientists in to potential causes, said Fiaschi, who now works at the InSAR company TRE ALTAMIRA. “And that’s, of course, necessary if you want to intervene or…make adjustments to protect the city.”

During both periods, research showed that much of Greater New Orleans was stable, sinking or rising by less than 2 millimeters per year.

But a few hot spots revealed larger changes. For example, the area in and around the Louis Armstrong International Airport sank by up to 27 millimeters per year between 2016 and 2020, likely because of construction of a new terminal during that time.

Areas of concrete floodwall near the airport and along sections of the Mississippi River, built as part of the city’s $15 billion Hurricane and Storm Damage Risk Reduction System, also sank by more than 10 millimeters per year as the floodwalls settled.

Identifying Problem Areas

About half of New Orleans is already below sea level; even a small change in elevation raises the risk of flooding.

The city’s infrastructure may already be showing the effects of subsidence, said Krista Jankowski, a geoscientist at the consulting firm Arcadis who lives in New Orleans but did not participate in the new research. Filled potholes become artificial high spots as the land around them continues to sink, and fire hydrant collars that used to be level with surrounding lawns now sit several inches higher.

Wetlands within and beyond the floodwalls are sinking, too. Both natural erosion and human-driven water removal could be contributing to this subsidence.

“It’s an existential consideration for people who live in New Orleans.”

Other areas are even gaining elevation in response to human activity—or lack thereof. The Michoud neighborhood, in the city’s Ninth Ward, rose by up to 6 millimeters per year between 2016 and 2020. Until 2016, groundwater extraction by a local power plant caused Michoud to sink. But when the plant was decommissioned and pumping stopped in 2016, the water table started to recover and the land began to rebound. That finding showed that at least some of the subsidence can be fixed.

“I think that’s a nice aspect of the study, that it updates earlier studies and documents what parts have been fixed and what parts are still a problem,” said Tim Dixon, a geologist at the University of South Florida who was not involved in the new research.

Monitoring and managing subsidence is “an existential consideration for people who live in New Orleans,” Jankowski said. Having a better understanding of where subsidence is concentrated and how quickly those areas are sinking, she explained, will help “make sure we’re paying attention to places where there may be issues.”

—Skyler Ware (@skylerdware.bsky.social), Science Writer

Citation: Ware, S. (2025), Parts of New Orleans are sinking, Eos, 106, https://doi.org/10.1029/2025EO250300. Published on 14 August 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.

Editors’ Highlights are summaries of recent papers by AGU’s journal editors. Source: Earth and Space Science

Measurements of bathymetry, the underwater depth of the ocean floor, are typically done for shallow coastal waters from boats with echosounders or from aircraft using green-wavelength lidar. However, these methods can be expensive to field, hard to update, and cannot access all locations.

NASA’s Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) mission has introduced a new satellite-derived shallow water bathymetry product that will provide free, easy-to-access, and ready-to-use measurements for the world’s shallow coastal waters. This information is of value for navigational safety, in particular for measurements in very shallow water or close to shore where boats cannot safely operate. Scientists can also use the data to study coral reefs and near-shore aquatic habitats.

The shallow water bathymetry product is derived using data from the ICESat-2 green-wavelength Advanced Topographic Laser Altimeter System (ATLAS) lidar, which operates from an orbit about 500 kilometers above the Earth’s surface.

Parrish et al. [2025] present their results of the first processing of the ICESat-2 archive, providing bathymetric measurements from approximately 0.5 to 21.5 meters depth for 13.7 million kilometers of coastal waters. This initial data set has been validated against high accuracy airborne bathymetry data acquired over eight locations in the eastern United States and the Caribbean islands. The products will be regularly updated as ICESat-2 acquires new data, filling in areas not initially measured because of rough seas or cloud cover and updating earlier measurements over time.

 ​Citation: Parrish, C. E., Magruder, L. A., Perry, J., Holwill, M., Swinski, J. P., & Kief, K. (2025). Analysis and accuracy assessment of a new global nearshore ICESat-2 bathymetric data product. Earth and Space Science, 12, e2025EA004391. https://doi.org/10.1029/2025EA004391

—Cathleen Jones, Editor, Earth and Space Science

Text © 2025. The authors. CC BY-NC-ND 3.0
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The 200,000 cubic metre collapse of a rock pillar has destroyed two extremely challenging climbing routes.

At a time when there is a great deal going on in the landslide world, another really interesting event has almost passed me by. Thanks to loyal reader Scott for highlighting another remarkable event.

Overnight on 1 – 2 August 2025, a large rock pillar collapsed at Carne Wall in the Blue Mountains of New South Wales in Australia. This has destroyed a series of famously challenging climbing routes. ABC News has a really good article about the landslide – they estimate that the volume was about 200,000 m3.

This collapse at Carne Wall is located at [-33.65233, 150.33885].

On Facebook, Monty Curtis has posted a nice before and after image pair:-

Before and after images of the 1-2 August 2025 rockfall at Carne wall in the Blue Mountains of Australia. Images by Monty Curtis.

And there is a really fantastic before and after drone video posted to Youtube by Simmo:-

Failures of this type would normally be via a topple, but I wonder if the debris field supports that interpretation? An alternative might be that the toe of the pillar failed and collapsed, with the subsequent pillar failure involving more vertical movement. This still from Simmo’s video shows that the pillar had a remarkably narrow base, which would have been under a high compressive load.

A still from a drone video collected a week before the 1-2 August 2025 rockfall at Carne wall in the Blue Mountains of Australia. Video posted to Youtube by Simmo.

Perhaps the base of the pillar underwent progressive failure, leading to the collapse of the mass?

Either way, it was fortunate that there were no climbers on the pillar when it failed.

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body {background-color: #D2D1D5;} Research & Developments is a blog for brief updates that provide context for the flurry of news that impacts science and scientists today.

The Mendenhall River in Juneau, Alaska, reached a record-breaking crest Wednesday morning thanks to a glacial outburst flood (GLOF) from Suicide Basin. At 16.65 feet, the crest exceeded the previous record flood stage of 15.99 feet in 2024.

Image created for the National Weather Service webpage monitoring Suicide Basin, www.weather.gov/ajk/suicidebasin

As glaciers melt, they leave behind lakes that rest in valleys. The melting of the Suicide Glacier has created a glacial lake in Suicide Basin, which lies above the Mendenhall Glacier. The Mendenhall Glacier, about 12 miles (19 kilometers) north of Juneau, acts as an ice dam for the lake. But, when enough snowmelt and precipitation occur, the lake drains through and over the glacier into Mendenhall Lake and the Mendenhall River.

The basin has filled and drained at least 39 times since July 2011, according to the National Weather Service.

During the crest on Wednesday morning, a gauge at Mendenhall Lake recorded a peak streamflow of 47,700 cubic feet per second (1,350 cubic meters per second), according to USGS data. In August 2023, the same gauge recorded a streamflow of 25,200 cubic feet per second (714 cubic meters per second), which Andrew Park, a meteorologist at NWS Juneau, called “historic”  at the time. The highest recorded streamflow before that was 16,300 cubic feet per second (462 cubic meters per second), in 2016. During the 2023 event, Rick Thoman, Alaska Climate Specialist at the Alaska Center for Climate Assessment and Policy, also told Climate.gov that “Decades worth of erosion happened in one weekend.”

The City and Borough of Juneau installed barriers provided by the United States Army Corps of Engineers earlier in 2025. According to the city and borough’s website, the barriers are intended to be an “interim solution,” but are designed to protect against GLOFs up to 18 feet high (5.4 meters). According to USA Today, the barriers seem to have successfully held back most of the water.

 
Related

•  Suicide Basin Monitoring and Current Conditions
•  Juneau Glacial Flood Dashboard
•  National Weather Service Flood Statement
•  Update: Mendenhall River crests, levels now falling
 

A flood statement issued by the National Weather Service in Juneau urged residents to heed road closures and local emergency management team guidance.

Water levels above 15 feet are considered the “major flood stage.” Zoe Kaplan, a meteorologist at the National Weather Service in Juneau, said the office predicts levels will drop to moderate flood stage (below 12 feet) by early afternoon, and to minor flood stage (below 10 feet) by late afternoon.

GLOFs could grow more common as rising temperatures increase glacier melt around the world. A 2020 study found that the number, total volume, and total area of glacial lakes have each increased by about 50% between 1990 and 2018. And, according to the Environmental Protection Agency, Alaska has warmed faster than any other U.S. state, and faster than the global average, over the past 100 years.

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

These updates are made possible through information from the scientific community. Do you have a story idea about science or scientists? We’re listening! Send us a tip at eos@agu.org. Text © 2025. AGU. CC BY-NC-ND 3.0
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For more than 50 years, scientists have debated whether a massive ice shelf—up to 1 kilometer thick—covered the entire Arctic Ocean during past ice ages, transforming the frigid water into a solid icy surface similar to Antarctica’s Ross Ice Shelf.

The hypothesis dates to the 1970s, when British glaciologist John Mercer and others proposed that during extremely cold periods, continental ice sheets would have extended far into the Arctic Ocean. It gained support in the 1990s when researchers began finding evidence of scouring on the seafloor, indicative of large, kilometer-thick ice running aground.

“We found out that even close to the Norwegian coast, there was still open water, which completely contradicts the hypothesis of a big ice shelf covering the Arctic Ocean.”

But new data published in Science Advances add evidence against such a “pan-Arctic” ice shelf, instead suggesting that seasonal sea ice, rather than a continuous ice shelf, dominated parts of the Arctic Ocean over the past 750,000 years.

“We found out that even close to the Norwegian coast, there was still open water, which completely contradicts the hypothesis of a big ice shelf covering the Arctic Ocean,” said coauthor Gerrit Lohmann, a climate modeler from the Alfred-Wegener-Institut in Germany. However, some experts argue that the results alter merely the timing and location of Arctic ice shelves.

Reading Ancient Algae

Instead of analyzing seafloor scars, the study’s authors looked at what was living in ancient seafloor sediment. They analyzed two sediment cores drilled from the Arctic Ocean between Europe and Greenland, searching for molecules produced by marine algae such as diatoms and dinoflagellates before the organisms died and sank to the seafloor.

Some species of alga grow on the underside of seasonal sea ice, and others thrive in open water. Their presence or absence within sediment deposited at a given time signals whether sea ice was present when they were living. Levels of calcium in the sediment can also indicate the production of marine organisms in surface waters.

By searching for organisms’ unique chemical signatures in dated sections of the cores, the scientists could conclude whether and when a solid ice shelf completely covered the ocean surface.

The results showed evidence of both seasonal sea ice and open water over the past 750,000 years, with one exception, around 676,000 years ago, when the chemical signature of the key marine life decreased for roughly 55,000 years.

On a train home after a funding interview, the study’s first author, Jochen Knies, was discussing the sediment core findings with Lohmann, who immediately recognized that the computational climate model he worked on, the high-resolution AWI Earth System Model, might offer additional data on the sea ice conditions during that time. “We discussed it for hours, maybe disturbing others on the train,” Lohmann said.

After some testing, he found that the model independently predicted that the same regions covered by the core samples would have had open water and seasonal sea ice instead of a continuous ice shelf, even during the coldest periods. “I was fascinated to see that in the time slices that [Knies] was interested in, the sea ice was even partly absent in summer,” Lohmann said of the modeling results. “It was completely the opposite of other hypotheses.”

“I would have assumed that where they found open water, there should have been times when this Arctic Ocean ice shelf moved into the area, and apparently it didn’t,” said Johan Nilsson, a paleoceanographer at Stockholm University in Sweden who was not involved in the new study but has published seafloor evidence of an Arctic Ocean ice shelf.

The Debate Continues

To Nilsson, the results don’t completely refute the possibility of large Arctic Ocean ice shelves; instead, they redefine their possible boundaries. “I think for me, it pushes back the edge of Arctic Ocean ice shelves a bit further north of Svalbard,” Nilsson said.

The authors of the new study “don’t see ice shelves in the Norwegian-Greenland sea, but that doesn’t mean that they didn’t exist in the Arctic.”

Leonid Polyak, a retired paleoceanographer at the Ohio State University who was not involved in the research, said the new study reveals “a very strong set of data.” He noted, however, that the evidence for Arctic ice shelves is strong, and the debate over whether they came together into one pan-Arctic ice shelf is “a bit overblown.”

“Pretty much everyone agrees that there have been ice shelves in the Arctic Ocean. The question is, When exactly did they exist, for how long, and where?” Polyak said. The authors of the new study “don’t see ice shelves in the Norwegian-Greenland sea, but that doesn’t mean that they didn’t exist in the Arctic.”

Lohmann acknowledged that mysteries remain in the Arctic and that the pan-Arctic ice shelf debate may not be settled. “I feel the final word hasn’t been spoken,” he said.

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

Citation: Chapman, A. (2025), Arctic ice shelf theory challenged by ancient algae, Eos, 106, https://doi.org/10.1029/2025EO250298. Published on 13 August 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.

Source: AGU Advances

What do many baked goods and the planet Mercury have in common? They shrink as they cool.

Evidence suggests that since it formed about 4.5 billion years ago, Mercury has continuously contracted as it has lost heat. And somewhat like a fresh-baked cookie or cheesecake, Mercury also cracks as it cools: Thrust faults cut through the planet’s rocky surface to accommodate the ongoing shrinking.

By observing how faults have uplifted parts of Mercury’s surface, researchers can begin to estimate how much Mercury has contracted since it formed. However, prior estimates have varied widely, suggesting that thanks to faulting resulting from cooling, Mercury’s radius has shrunk by anywhere from about 1 to 7 kilometers.

To resolve this discrepancy, Loveless and Klimczak employed an alternative method for estimating shrinkage caused by cooling-induced faulting on Mercury.

Prior estimates all relied on a method that incorporates the length and vertical relief of uplifted landforms, but that produces different shrinkage estimates depending on the number of faults included in the dataset. In contrast, the new method’s calculations are not reliant upon the number of faults. Rather, it measures how much the largest fault in the dataset accommodates shrinkage, then scales that effect to estimate the total shrinkage.

The researchers used the new approach to analyze three different fault datasets: one including 5,934 faults, one including 653 faults, and one including just 100 faults. They found that no matter which dataset was used, their method estimated about 2 to 3.5 kilometers of shrinkage. Combining their results with prior estimates of additional shrinkage that may have been caused by cooling-induced processes other than faulting, the researchers concluded that since Mercury’s formation, the planet’s radius may have shrunk by a total of 2.7 to 5.6 kilometers.

The new estimates could help deepen the understanding of the long-term thermal history of Mercury. Meanwhile, the authors suggest, the same methodology could be used to investigate the tectonics of other planetary bodies, like Mars, that feature faults. (AGU Advances, https://doi.org/10.1029/2025AV001715, 2025)

—Sarah Stanley, Science Writer

Citation: Stanley, S. (2025), How much has Mercury shrunk?, Eos, 106, https://doi.org/10.1029/2025EO250301. Published on 13 August 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.

Editors’ Highlights are summaries of recent papers by AGU’s journal editors. Source: Geophysical Research Letters

The Pacific Decadal Oscillation (PDO) is a slowly evolving pattern of ocean temperature anomalies in the North Pacific that can influence climate and ecosystems across the globe. The climate science community and stakeholders are increasingly interested in how well we can predict the PDO from months to years in advance, but such predictions are not equally reliable at all times of year. As the PDO is part of a coupled ocean-atmosphere system, such simulations are very resource intensive.

Meeker et al. [2025] use the Seasonal to Multi Year Large Ensemble (SMYLE)—a large ensemble of initialized decadal hindcast simulations with the fully coupled Community Earth System Model 2 (CESM2)—to show that while the PDO is predictable up to one year in advance, skill drops off most rapidly during late fall and spring, a seasonal pattern that mirrors known challenges in forecasting El Niño events in the tropical Pacific. Using a simple statistical model, the authors further show that much of the PDO’s predictability comes from persistence—the ocean’s tendency to stay in the same state for a while—but atmospheric teleconnections from the tropical Pacific also play an important role.

The results highlight that when El Niño is hard to predict, so is the PDO. Understanding when and why these prediction skill drops happen is important for improving seasonal forecasts that support fisheries, agriculture and water management. This work also shows how relatively simple linear models can help diagnose behavior in more complex models of the coupled climate system, enabling benchmarking and improvement of more advanced forecasting systems.

Citation: Meeker, E. D., Maroon, E. A., Deppenmeier, A. L., Thompson, L. A., Vimont, D. J., & Yeager, S. G. (2025). Seasonality of pacific decadal oscillation prediction skill. Geophysical Research Letters, 52, e2025GL116122. https://doi.org/10.1029/2025GL116122

—Kristopher B. Karnauskas, Editor-in-Chief, Geophysical Research Letters

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.

The location of this major event has now been identified. It was a major rock slope failure that ran out across the South Sawyer Glacier.

The Alaska Earthquake Center has now provided a detailed update about the 10 August 2025 landslide that occurred in the area of Tracy Arm. This work has been led by Ezgi Karasözen, one of the Earthquake Center’s research scientists, so the credit must go to them.

They have posted a very informative page that describes the seismic detection of the landslide, provides eyewitness accounts of the damage that it caused and outlines how they have gone about finding the landslide. This is unusually good public communication about a large event – so well done to them.

They have also published some imagery from their initial reconnaissance of the landslide. Meanwhile, they have also posted to Facebook a short video of the landslide itself – Wordpress won’t allow me to embed this, so this is the link:-

https://www.facebook.com/reel/2164841844024421

The footage was captured by LT Chip Baucom and CDR PJ Johansen of the U.S. Coast Guard. There are two stills that are very helpful in providing an initial view of this landslide. First, this is view of the scar and the deposit – note that the landslide has failed onto the  South Sawyer Glacier.

An initial view of the 10 August 2025 landslide onto the South Sawyer Glacier. Image from a video collected by the US Coast Guard, posted to Facebook by the Alaska Earthquake Center.

This appears to be a large, joint-controlled rock slope failure, with the appearance of a wedge (or several wedges, perhaps).

Second, the video captures the track of the landslide down the glacier towards the fjord:-

An initial view of the track of the 10 August 2025 landslide over the South Sawyer Glacier. Image from a video collected by the US Coast Guard, posted to Facebook by the Alaska Earthquake Center.

This appears to have been a landslide with high mobility – probably the consequence of a large volume and the movement over a low friction surface (ice).

The Alaska Earthquake Center highlights that the seismic instruments detected about 100 small events in the hours leading up to the final collapse. This will be a rich dataset to understand the failure process.

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As a Ph.D. student studying the impacts of coastal flooding in Annapolis, Md., Miyuki Hino heard from people familiar with the area that rain caused flooding, but the conventional method of measuring floods wasn’t picking it up.

Tide gauges located in oceans and bays, which Hino and other scientists typically use to detect coastal floods, do not necessarily reflect flooding on land, leaving researchers, city planners, and forecasters with little information about how often these floods occur. As Hino, now an environmental social scientist at the University of North Carolina at Chapel Hill, and others revealed in a new study published in Communications Earth and Environment, installing instruments in inland communities can reveal even small-scale or sunny-day flooding that can affect residents.

“The goal of our project overall is to better answer how flooding is affecting people, businesses, and communities in low-lying areas.”

In the new study, the researchers placed low-cost flood sensors on land in three coastal North Carolina communities to study how often any type of flooding—from nuisance flooding to larger events—occurs.

“The goal of our project overall is to better answer how flooding is affecting people, businesses, and communities in low-lying areas,” Hino said. The new study takes a critical first step by measuring flooding accurately, she said.

Hino and Katherine Anarde, a coauthor on the study and a coastal engineer at North Carolina State University, hope the findings motivate other scientists to think critically about how and where they measure floods in their own research, especially as sea level rise makes coastal flooding more common. 

Out with the Tide (Gauges)

Scientists typically define coastal flooding using thresholds determined by NOAA and the National Weather Service (NWS) that refer to certain tide gauge levels. These tide gauges sit in the ocean just offshore and measure the height of water as tides change. 

NWS uses these measurements to issue watches and warnings for coastal flooding of varying severities. But often, those tide gauges don’t measure “where flooding is experienced by people,” said Paul Bates, a hydrologist at the University of Bristol who was not involved in the new study.

Tide gauges don’t account for every factor that may lead to coastal flooding, such as runoff from rainfall, contributions from groundwater, and the effects of drainage infrastructure. They’re also sparse. That means tide gauge levels—and flood warnings—don’t always match what people see on the ground. 

To determine the scale of the problem, Hino, Anarde, and their colleagues installed networks of sensors and cameras near roadways and within storm drains in two towns and one unincorporated community in North Carolina: Beaufort, Carolina Beach, and Sea Level. The research team asked residents and municipal staff for the best spots to place the sensors to capture the actual flooding that the communities witness. 

After a full year of monitoring, they found that the NOAA high-tide flood threshold and the NWS minor flood threshold, which both rely on tide gauge data, were not consistent with occurrences of inland flooding. In some cases, the inland sensors picked up flooding as much as 10 times more often than the tide gauges suggested. NOAA thresholds consistently missed inland flooding, whereas NWS thresholds both overestimated and underestimated flood frequency, depending on the community. 

They also found that tide gauge data generally underestimated the duration of floods on land. One reason for the difference is that water may recede at a tide gauge fairly quickly but may take much longer to drain off land via stormwater infrastructure and groundwater infiltration. 

The results “demonstrate the many benefits of measuring water levels on land rather than relying on tide-gauge-based estimates,” the authors wrote.

“There haven’t been many studies of this local-scale surface water flooding anywhere in the world because it’s so difficult to instrument,” Bates said. The new study is “one of the best empirical demonstrations” of the fact that water levels at the coast, as measured by tide gauges, are not a good indicator of flooding experienced inland, he said. 

In their study, the researchers defined flooding as the presence of any water on a roadway, initially indicated by their sensors and confirmed by nearby cameras. When the camera view was obscured, a flood was counted when the sensors indicated water above the elevation of the roadway by at least the measurement error of their sensors. The shallowest flood measured in the study was 0.24 inch (0.6 centimeter), and the deepest was nearly 2 feet (61 centimeters).

Nuisance flooding, such as that seen here in Beaufort, N.C., is often not fully captured by tide gauges. Credit: Sunny Day Flooding Project/Flickr, CC BY-NC-ND 2.0

The study’s results may have been very different if the researchers had used a different definition of flooding, Bates pointed out. Flood events as defined in the study are very frequent and probably do not all create a nuisance for residents, he said.

The definition was chosen, Hino explained, because even small amounts of water can pose problems for some residents, depending on their needs. “We’re not in a position where we can say everybody needs to worry about flooding [at one depth], but no one needs to care [at another depth].” 

For example, she said, driving through even a small puddle of salt water can spray water onto the underside of one’s car, which can cause corrosion. Relatively shallow floods can limit land use, depress property values, rust low-lying infrastructure, and contaminate flooded areas, according to the Sunny Day Flooding Project, of which the new research was part.  

Meaningful Measurement

The sensors revealed what people across the state have been saying—that it’s flooding “all the time,” Anarde said. Because flooding is already posing problems for communities, the results increase the urgency of developing infrastructure solutions as sea levels rise, Hino said. 

“The places that we think as scientists are important to measure may not be in line with what communities are interested in keeping dry.” 

The data show that scientists aren’t always measuring the impacts of sea level rise and coastal flooding in places where such flooding affects communities, Anarde said. “The places that we think as scientists are important to measure may not be in line with what communities are interested in keeping dry.” 

She recommends that scientists studying flooding focus on installing instrumentation in places where residents see frequent flooding, which has the added benefit of facilitating trust between residents and scientists, too. 

“I don’t think our sensors are a silver bullet solution for measuring floods at every location,” Anarde said. “We can make our data useful in planning everyday activities by coming up with new ways to measure floods.”

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

Citation: van Deelen, G. (2025), Residents know when floods happen, but data must catch up, Eos, 106, https://doi.org/10.1029/2025EO250295. Published on 12 Auguste 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.

Source: Journal of Geophysical Research: Earth Surface

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

与单河道蜿蜒型河流相比，多河道辫状河通常处于植被稀疏、沉积物颗粒粗大且沙洲可移动的环境中。过去的研究认为，辫状河的路径随时间变化的方式是“混乱的”，因为它们的迁移取决于许多因素，包括河流形状和水位的变化。

然而，由于单个河道的迁移可能会影响洪水或侵蚀等灾害发生的可能性，因此了解这种迁移对于保护这些复杂水道周围的居民、结构和生态系统至关重要。

Li和Limaye研究了布拉马普特拉-贾木纳河（Brahmaputra-Jamuna River）长达180公里的河道，这条河位于孟加拉国，其河道已通过卫星图像得到很好的解译。

科学家们，以及生活在河道之间岛屿上的60万居民中的许多人已经知道，在夏季的季风季节，这条河的水位很高，而从1月到3月，水位一直维持在低水平。该研究团队使用了一种称为动态时间弯曲的统计方法，来绘制2001年至2021年期间河道大小、形状和路径的长期变化。这种技术使他们能够计算出河道中心线移动的程度和速度。然后，他们应用了一个现有的为蜿蜒型河流开发的模型，看看它是否也可以预测辫状河道的运动。

他们发现，布拉马普特拉-贾木纳河的迁移比以前认为的更容易预测。在研究期内，大约43%的河道是逐渐移动的，而不是突然移动的。平均而言，这些河道线比大多数蜿蜒型河流迁移得更快，每年的速度约为其宽度的30%。在某些情况下，这种迁移的速率与河道线的曲率密切相关，而在整体上，它与河道宽度的相关性较弱。

作者称，这些发现对未来研究辫状河道有重要意义。认识到至少有一些河道线是连贯迁移的，可能会为辫状河地区，特别是人口密集地区的侵蚀和洪水缓解工作提供信息。(Journal of Geophysical Research: Earth Surface, https://doi.org/10.1029/2024JF008196, 2025)

—科学撰稿人Rebecca Owen (@beccapox.bsky.social)

Read this article on WeChat. 在微信上阅读本文。

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

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

Climate models predict that rising greenhouse gas levels cool the stratosphere, while the healing of the Antarctic ozone hole—driven by the reduction of ozone-depleting substances under the Montreal Protocol since the beginning of the 21st century—should warm the Antarctic lower stratosphere. However, observations for the period from 2002 to 2022 reveal unexpected changes: warming in the Southern Hemisphere (SH) subtropical lower stratosphere and cooling over Antarctica.

Sweeney et al. [2025] identify the cause as a slowdown in stratospheric circulation that moves stratospheric air and chemicals from low to high latitudes. These circulation changes, which are most pronounced from October to December, lead to warming in the subtropical lower stratosphere of the Southern Hemisphere and cooling in the Antarctic lower stratosphere. They also mask the anticipated ozone recovery over Antarctica during this period. Accounting for these circulation changes removes the anomalous warming of the SH subtropical lower stratosphere and reveals an obvious Antarctic lower stratospheric warming and enhanced ozone recovery. These findings highlight the crucial role of the stratospheric circulation in shaping temperature and ozone changes.

Citation: Sweeney, A., Fu, Q., Solomon, S., Po-Chedley, S., Randel, W. J., Steiner, A., et al. (2025). Recent warming of the southern Hemisphere subtropical lower stratosphere and Antarctic ozone healing. AGU Advances, 6, e2025AV001737. https://doi.org/10.1029/2025AV001737

—Donald Wuebbles, Editor, AGU Advances

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The most severe rainfall event ever recorded in Nepal impacted about 2.6 million people, causing losses of US$370 million and about 270 lives.

Between 26 and 28 September 2024, a devastating late monsoon rainfall event in Nepal triggered hundreds of landslides. In landslide terms, this was the most serious event recorded in Nepal outside of a major earthquake – economic losses are estimated to have been 1% of the country’s GDP and about 270 people were killed or left missing.

An initial analysis (Lamichhane et al. 2025 – the paper is behind a paywall, but the link should allow you to access it) has just been published in the journal Landslides – a very welcome paper. The authors, the majority of whom are Nepali, deserve praise for the speed at which this has been compiled, its comprehensive analysis and the diligence with which they have provided location information for the major events they describe. This is a model that others should seek to follow.

A substantial part of the paper examines the rainfall event itself. In central Nepal, 25 weather stations recorded their highest ever 24 hour rainfall. One station, at Godavari in Lalitpur District, recorded 311.6 mm. Peak hourly intensities were also high by Nepal standards – Godavari recorded 26.8 mm between 7 and 8 pm on 28 September 2024 – again, an unusually high figure for Nepal. Over the three day period, Godavari recorded 366.0 mm of rainfall.

Lamichhane et al. (2025) rightly highlight that the disaster was probably the consequence of a rainfall event that occurring in the late monsoon period, when the ground is already saturated, and that then involved high rainfall intensities, a high 24 hour rainfall total and a high 72 hour rainfall total. This is a toxic combination.

Lamichhane et al. (2025) then describe some of the more serious landslide events. The greatest losses occurred were caused by the Jhyaple Khola landslide, situated on the Tribhuvan Rajpath highway. The location is [27.71146, 85.20236] – the site is shown in the Google Earth image below, with the marker showing the point at which the landslide struck the road:-

Google Earth image of the site of the Jhyaple Khola landslide in Nepal, collected on 12 December 2023.

This is a Google Earth image of the site after the landslide:-

Google Earth image of the aftermath of the Jhyaple Khola landslide in Nepal, collected on 7 June 2025.

And here is a slider to allow you to compare the two:-

This landslide occurred at about 4 am on 28 September 2024. Unfortunately, two buses were at the site, trapped behind an earlier landslide.

Both buses were struck, killing 35 people. Lamichhane et al. (2025) describe the landslide as a 3 m deep debris flow that was rich with large pieces of woody debris. They rightly point out that the failure originated about 80 m above the road, but I would also highlight that the source appears to be another section of road. It is unclear to me as to whether the failure was on the cut slope above the road or a fill slope below it. That road appears on images from 2004, so it is not new.

Lamichhane et al. (2025) detail many other examples of landslides across Central Nepal, and even these are just a fraction of the total. Whilst the rainfall was unprecedented, they rightly highlight the anthropogenic issues that were the root of the disaster:-

“Major landslides and debris flow sites were linked to intense rainfall, unregulated sand mining, poorly managed rivers, haphazard road construction, and highly weathered slopes.”

In addition, they note that the following about the aftermath of the incident:-

“Despite involvement from various agencies, the disaster response fell short, underscoring the need for a more proactive approach to mitigation and management. Public response to rainfall warnings from agencies like Nepal’s Department of Hydrology and Meteorology (DHM) was also insufficient, contributing to tragic fatalities.“

Nepal will face many more events like this in the coming years, and indeed an even larger rainfall event is probably just around the corner. Lamichhane et al. (2025) demonstrates that immediate action is needed. Sadly, I have low confidence that this occur. It feels inevitable that I will describe another event of this type on this blog in the coming years.

Reference

Lamichhane, K., Biswakarma, K., Acharya, B. et al. 2025 Preliminary assessment of September 2024 extreme rainfall–induced landslides in Central Nepal. Landslides. https://doi.org/10.1007/s10346-025-02577-w

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Source: Journal of Geophysical Research: Planets

Despite being thinner and drier than Earth’s atmosphere, Mars’s atmosphere contains clouds composed of tiny water ice crystals. And just as on Earth, these clouds influence the planet’s climate. However, most of what we know about clouds on Mars comes from data collected during the Martian afternoon, so there is still much to learn about how clouds tend to form and dissipate over a full day.

Using data from the Emirates Mars Mission Hope probe, which has orbited Mars since 2021, Atwood et al. have captured the first comprehensive view of nighttime clouds on Mars.

Hope’s high-altitude, low-inclination elliptical orbit was specifically designed to enable observation across all times of day and night and at almost all latitudes and longitudes. The researchers analyzed data collected over nearly two Martian years by the Emirates Mars Infrared Spectrometer, an instrument mounted on Hope that can detect the presence and thickness of clouds, according to how they absorb and scatter infrared light.

The analysis revealed that for much of the Martian year, nighttime clouds are, on average, thicker than daytime clouds. Peaks in cloudiness typically occurred in the early morning and the evening, separated by a midday minimum.

During the cold season on Mars, thick clouds tended to form in a band near the equator, becoming thickest just after sunrise. Also during the cold season, late-evening clouds typically formed in a broader distribution across low latitudes, while early-morning clouds mostly concentrated over a vast volcanic region known as Tharsis, which covers the equator and low latitudes.

These findings shed new light on Martian atmospheric dynamics and could help scientists validate computational models of Mars’s atmosphere, the researchers say. (Journal of Geophysical Research: Planets, https://doi.org/10.1029/2025JE008961, 2025)

—Sarah Stanley, Science Writer

Citation: Stanley, S. (2025), First complete picture of nighttime clouds on Mars, Eos, 106, https://doi.org/10.1029/2025EO250279. Published on 11 August 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.

Editors’ Highlights are summaries of recent papers by AGU’s journal editors. Source: Water Resources Research

Coal seam gas (CSG) is extracted by pumping out groundwater, which lowers underground pressure, can lead to shrinking of geological layers and make the ground above sink over time.

Cui et al. [2025] present a new way to understand and predict land subsidence caused by CSG extraction. The study introduces a model that links groundwater flow with how the ground moves, including both general sediment compression and the shrinkage of coal as gas is removed. It uses real-world data, such as groundwater levels, gas production, and satellite measurements, to improve the model’s accuracy. By testing this model in the Surat Basin (Queensland, Australia), the authors find that subsidence can reach up to 235 millimeters near some wells and follows a three-stage pattern: growth, stabilization, and partial recovery.

The model helps separate reversible and permanent parts of the subsidence, which is important for long-term planning. This work is especially useful for land managers and farmers concerned about how CSG production may affect agriculture and drainage. More broadly, it provides a practical tool for evaluating the environmental impacts of energy extraction.

Citation: Cui, T., Schoning, G., Gallagher, M., Aghighi, M. A., & Pandey, S. (2025). A coupled hydro-mechanical modeling framework to concurrently simulate coal seam gas induced subsidence and groundwater impacts. Water Resources Research, 61, e2024WR039280.  https://doi.org/10.1029/2024WR039280  

—Gabriel Rau, Associate Editor, Water Resources Research

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Seismic data and eye-witness reports of a displacement wave point to a large landslide at 5:30 am.

On 10 August 2025, at 5:30 am local time, the Alaska Earthquake Center detected a seismic signal that was almost certainly generated by a landslide. They have posted the record of the seismic signal to Twitter. Their posting included a record of the seismic signal, which looks fairly typical for a landslide:-

The seismic signal from Tracy Arm in Alaska, which was probably generated by a large landslide. Data released by the Alaska Earthquake Center.

There are eye witness reports of the resultant localised displacement wave. BNO News quotes a kayaker who was camping in the affected area.

“Kayaker Sasha Calvey said she and two others were camping on Harbour Island in Tracy Arm Inlet, a fjord about 45 miles south of Juneau, when a landslide or iceberg caused a tidal surge that swept away half of their gear, including one boat, personal items, and cooking equipment.

“Calvey said their gear had been stored about 25 feet above the high tide line, but the water reached it and came within an inch of sweeping away their tent. She added that they placed a radio distress call that was picked up by a boat, which transported them to Juneau.”

The mouth of Tracy Arm is at [57.7778, -133.6167]. This is the latest Planet Labs image of at least a part of the area, captured on 7 August 2025 (last Thursday):-

Satellite image of Tracy Arm inlet. Image copyright Planet Labs, used with permission. Image dated 7 August 2025.

This is steep and rugged terrain, but the image provides no obvious hint of the location of the landslide that occurred three days later, as far as I can see. Hopefully, someone will capture a satellite image in the next few days that will shed light on the location, but that will depend upon the weather. Alternatively, the location might be identified from a boat or from an aerial survey.

I will undoubtedly return to this theme in the coming days.

Reference

Planet Team 2024. Planet Application Program Interface: In Space for Life on Earth. San Francisco, CA. https://www.planet.com/

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This is an authorized translation of an Eos article. Esta es una traducción al español autorizada de un artículo de Eos.

Los arrecifes de coral son ecosistemas vitales que sustentan la vida marina, el ecoturismo y la protección costera. Ellos también guardan algo valioso bajo su superficie: registros del pasado del océano. Bajo la capa exterior viva de los corales masivos se encuentran estructuras esqueléticas tipo roca que contienen bandas anuales, similares a los anillos de árboles. Los científicos pueden estudiar las condiciones en el momento en que estas bandas se formaron mediante la perforación, recuperación y análisis de núcleos, algunos de los cuales representan siglos de crecimiento coral.

Daren Coker (izquierda) y Thomas DeCarlo perforan un núcleo de coral en el Mar Rojo. Crédito: Morgan Bennett-Smith

Desde la década de 1970, los estudios de núcleos de coral pueden determinar patrones de crecimiento pasados, un campo conocido como esclerocronología coralina, han producido descubrimientos científicos notables. Knutson et al. [1972] encontraron que las bandas anuales están compuestas por bandas de alta y baja densidad que reflejan patrones de crecimiento estacional. Hudson [1981] descubrió que, por lo general, las bandas de alta densidad se forman durante el crecimiento invernal más lento, mientras que las de baja densidad se forman durante el crecimiento del verano más rápido y que el crecimiento variable a largo plazo de corales están influenciadas por la calidad del agua y los efectos del desarrollo costero. Algunos núcleos también contienen “bandas de estrés” de alta densidad, formadas debido a eventos de blanqueamiento de corales u otros desafíos medioambientales [Lough, 2008]. En conjunto, estas bandas proporcionan información sobre la historia del crecimiento de coral, lo que permite a los científicos construir modelos de edad confiables de las condiciones oceánicas y climáticas pasadas.

Hoy en día, los métodos usados para investigar núcleos de corales han avanzado considerablemente. Junto con otros métodos, como los análisis de isótopos estables y de radio elementales, la tomografía computarizada (CT) desempeña un rol fundamental en la obtención de datos que ayudan a revelar los parámetros de crecimiento coralino. Los científicos pueden escanear rayos X en 2D y escaneo CT 3D para examinar las estructuras internas de núcleos coralinos, incluyendo sus bandas de densidad anual [Knutson et al., 1972; Hudson, 1981; Lough, 2008; DeCarlo et al., 2025]. En algunos casos, este análisis involucra incluso la visita de un científico a un hospital local para usar su equipo de CT – un paciente inesperado para el técnico de radiología.

Esta animación de una tomografía computarizada muestra un corte transversal de un núcleo de coral. Los pequeños círculos dentro del núcleo son coralitos, las estructuras esqueléticas individuales formadas por pólipos de coral. Crédito: USGS, Dominio público Un núcleo coralino se encuentra en la mesa de examen de un equipo de tomografía computarizada en un hospital antes de ser escaneado. Crédito: Thomas DeCarlo

Sin embargo, no se había realizado un archivo sistemático de datos de imágenes de núcleos coralinos, en parte debido a la falta de un repositorio adecuado. Esta brecha presenta el riesgo de perder imágenes valiosas e impide un intercambio ágil y transparente de las interpretaciones científicas de estas imágenes. Por lo tanto, un repositorio centralizado, virtual y de acceso abierto de imágenes de núcleos coralinos es crucial para fomentar la transparencia científica y preservar estos recursos para investigaciones futuras.

Una aplicación para organizar un repositorio

La aplicación CoralCT se desarrolló para consolidar y organizar escáneres de núcleos coralinos en un repositorio virtual que permite el archivo digital y el análisis de imágenes [DeCarlo et al., 2025]. Actualmente, el repositorio contiene más de 1,000 escaneos de corales recolectados en una amplia gama de regiones de arrecifes coralinos, que incluye la Gran Barrera de Coral, el Caribe y el Mar Rojo. Estos escaneos coralinos han sido aportados por individuos y agencias, como el Servicio Geológico de Estados Unidos (USGS, por sus siglas en inglés) y la Oficina Nacional de Administración Oceánica y Atmosférica (NOAA, por sus siglas en inglés).

Investigadores coralinos suben escaneos de rayos X o de CT a CoralCT y, cuando están listos, pueden hacer que sus datos estén públicamente disponibles para cualquier persona con una computadora y conexión a internet. Este enfoque de transparencia fomenta la colaboración entre investigadores de núcleos coralinos, quienes pueden consultar el directorio de núcleos de la aplicación y ver quién más ha recolectado núcleos en sus áreas de interés. Esto también ayuda a evitar la duplicación innecesaria de esfuerzos de investigación, lo cual es especialmente importante dada la necesidad de reducir el impacto del muestreo en los corales, muchos de los cuales son especies en peligro de extinción.

Utilizando las herramientas analíticas de la aplicación, los observadores pueden mapear las bandas de densidad anuales en núcleos coralinos para extraer datos sobre la tasa de crecimiento y la densidad esquelética. Tal como en estudios de anillos de árboles, este tipo de análisis ofrece información sobre las condiciones medioambientales pasadas, ya que el crecimiento de corales puede responder con sensibilidad a la variabilidad climática.

Por ejemplo, Barkley et al. [2018] utilizaron CoralCT para visualizar bandas de estrés de alta densidad y reconstruir la historia del blanqueamiento de corales a lo largo de seis décadas en un arrecife remoto del Océano Pacífico ecuatorial, donde el monitoreo de datos es escaso. Rodgers et al. [2021] midieron las tasas de crecimiento anual en CoralCT para rastrear la recuperación de corales frente a Kaua’i, Hawaii, en los 15 años posteriores a un evento de inundación devastadora. Más recientemente, DeCarlo et al. [2024] aprovecharon la amplitud de núcleos en CoralCT para reconstruir patrones de crecimiento coralinos en las décadas y siglos recientes a lo largo de miles de kilómetros en el Indo Pacífico.

Rescatando registros antiguos y recolectando nuevos

Archivar datos valiosos que de otro modo podrían perderse es el propósito fundamental de CoralCT. Un destacable ejemplo de cómo cumple este propósito involucra el rescate y la digitalización de imágenes de rayos X de más de 20 núcleos recolectados en el Océano Pacífico entre la década de los 1980 y principios de 2000. Las películas de rayos X, previamente guardadas por un científico jubilado, ahora están archivadas y disponibles para su análisis en CoralCT.

Colecciones más antiguas como estas pueden proporcionar información valiosa sobre el crecimiento coralino antes de que las perturbaciones medioambientales, como el blanqueamiento masivo por estrés térmico, comenzaran a afectarlos.

En un esfuerzo similar, la USGS escaneó recientemente núcleos coralinos en TC que datan de finales de la década de los 1960, algunos de los núcleos más antiguos jamás recolectados [Hudson et al., 1976]. Estos escaneos se están incorporando al repositorio para que puedan ser reanalizados por investigadores ahora y en el futuro. Colecciones más antiguas como estas pueden proporcionar información valiosa sobre el crecimiento coralino antes de que las perturbaciones medioambientales, como el blanqueamiento masivo por estrés térmico, comenzaran a afectarlos.

Además, a estas contribuciones históricas, el repositorio CoralCT continúa creciendo con la incorporación de nuevos datos. Una contribución reciente incluye escaneos de núcleos de arrecifes recolectados en la costa de Hawai’i en 2023 durante la Expedición 389 del Programa Internacional Ocean Discovery. Los núcleos de arrecifes difieren de los núcleos coralinos en composición y estructura, pero también son cruciales para entender la historia oceánica y el cambio medioambiental. Durante la expedición 389, se recolectaron núcleos de arrecifes sumergidos que una vez crecieron cerca de la superficie del océano, pero que dejaron de calcificarse a medida que se sumergían en aguas profundas. Estos núcleos de arrecifes contienen coral fragmentado, algas coralinas, microbialitos y otros materiales constructores de arrecifes, cuyas composiciones permiten a los científicos mirar milenos hacia el pasado y descubrir registros valiosos del nivel del mar y el cambio climático.

Análisis repetibles, resultados verificables

Cuando no se archivan imágenes de núcleos coralinos originales, sin procesar, el valor de las mediciones de crecimiento y otros análisis es limitado porque otros científicos no pueden verificarlos fácil e independientemente. Esto es problemático ya que la ciencia se basa fundamentalmente en la capacidad de repetir experimentos y verificar resultados, sobre todo considerando que investigadores individuales pueden introducir subjetividad y posibles sesgos incluso en interpretaciones de datos altamente sistemáticas y rigurosas. A medida que los conjuntos de datos se hacen más grandes, complejos y numerosos, mantener la transparencia es cada vez más importante, pero también cada vez más difícil.

En esta captura de pantalla de un núcleo coralino analizado en la aplicación CoralCT, las líneas naranjas en la imagen del núcleo indican dónde un observador ha mapeado las bandas de densidad anual. Crédito: Avi Strange

CoralCT aborda estos desafíos garantizando que toda la información y el contexto de un núcleo estén completamente documentados, accesibles y descargables. Esta información incluye metadatos esenciales tales como el origen del núcleo, los detalles de propiedad, la fecha de recolección, la profundidad y la identificación de especies. Y lo que es más importante, CoralCT archiva los mapas de bandas anuales definidos el usuario para derivar datos de la tasa de crecimiento [DeCarlo et al., 2025], asegurando que estos datos e interpretaciones sean totalmente reproducibles y estén abiertos a la verificaciones de otros.

Esta transparencia también se comparte entre los observadores dentro de la aplicación. Cuando un usuario mapea las bandas de un núcleo, este puede agregar notas y captura de pantalla que otros usuarios pueden ver mientras analizan dicho núcleo. Más aún, cuando un usuario termina de mapear las bandas de un núcleo y procesa los datos, esta información se almacena y se puede descargar para que otros científicos la consulten. Esta capacidad permite a los científicos realizar estudios con múltiples observadores, lo que puede reducir posibles sesgos introducidos por la observación individual.

Un desafío que hemos encontrado en nuestros esfuerzos para ampliar CoralCT ha sido la reticencia en algunos investigadores y programas a compartir datos.

A pesar de estas ventajas, un desafío que hemos encontrado en nuestros esfuerzos para ampliar CoralCT ha sido la reticencia en algunos investigadores y programas a compartir datos debido a la preocupación por las infracciones de propiedad intelectual y la “apropiación indebida” de datos prepublicados. Esta reticencia, que es entendible considerando la falta de transparencia y protección para los propietarios de los datos en las prácticas previas de gestión de datos, puede lamentablemente limitar los avances científicos y las colaboraciones que podrían ayudar a abordar el cambio climático, la degradación de arrecifes coralinos y otros desafíos complejos.

Para abordar estas preocupaciones, CoralCT ofrece controles privados a los propietarios de núcleos, que pueden usar para restringir el acceso a sus escaneos y a los datos derivados. Estos controles son particularmente útiles cuando los núcleos son parte de una investigación en curso que aún no se ha publicado o están sujetos a una moratoria posterior al crucero, lo que garantiza que datos sensibles permanezcan protegidos hasta que la investigación esté lista para ser compartida. Además, cada núcleo está identificado con el propietario de los datos, agradecimientos y citas relevantes.

Avanzando hacia la accesibilidad y colaboración

CoralCT también representa un camino para hacer la ciencia más inclusiva y accesible. La aplicación está diseñada con una interfaz fácil de usar e incluye recursos tales como videotutoriales y una guía de usuario paso a paso para ayudar a presentar sus funciones a un público amplio. Recientemente, también se crearon planes de clase para estudiantes de educación media y básica que guían a los estudiantes en el mapeo de las bandas de núcleos de coral en la aplicación, ofreciendo maneras accesibles de explorar las ciencias marinas.

Un estudiante de secundaria que visita el Laboratorio de Esclerocronología de la Universidad de Tulane usa un casco de realidad virtual para interactuar con núcleos coralinos en 3D durante el evento “Boys at Tulane in STEM 2025” de la universidad. Crédito: Danielle Scanlon Estudiantes de secundaria aprenden sobre núcleos de coral gracias a un holograma en un taller de la Universidad del Pacífico de Hawái. Crédito: Thomas DeCarlo

El potencial educacional de la aplicación se demostró en recientes eventos de divulgación. Utilizando tecnología de realidad virtual, estudiantes de secundaria en Nueva Orleans visualizaron escaneos 3D de núcleos de corales desde CoralCT y practicaron la identificación de bandas de densidad anual. En un evento similar, estudiantes de sexto grado en Hawái interactuaron con núcleos holográficos 3D coralinos y aprendieron cómo los científicos los extraen y estudian para comprender los patrones de crecimiento a lo largo del tiempo. Las experiencias positivas de estudiantes y profesores durante estos eventos demostraron cómo CoralCT brinda la oportunidad de interactuar de forma práctica con datos científicos reales.

La integración de IA también podría, y esto es importante, facilitar que todos los usuarios contribuyan al análisis de núcleos coralinos, independientemente de su formación académica o experiencia de campo.

De cara al futuro, existe la posibilidad de integrar inteligencia artificial (IA) en CoralCT para la identificación automatizada de patrones de bandas de coral. Si un sistema de IA se entrenara con interpretaciones humanas existentes, podría sugerir automáticamente marcas de bandas que los usuarios podrían revisar y verificar. Este avance ofrece la posibilidad de realizar análisis de núcleos coralinos más precisos y eficientes, manteniendo la supervisión humana. La integración de IA también podría, y esto es importante, facilitar que todos los usuarios contribuyan al análisis de núcleos coralinos, independientemente de su formación académica o experiencia de campo. Cada nueva contribución o análisis de un núcleo mejora la base de datos CoralCT y amplía nuestro conocimiento de los arrecifes de coral y las condiciones oceánicas pasadas.

La esclerocronología coralina es vital para comprender los cambios medioambientales en los ecosistemas de arrecifes coralinos y los impactos que estos cambios han provocado. Gracias a esta investigación, obtenemos información sobre el pasado del océano y mejoramos nuestra comprensión de los arrecifes de coral actuales. A medida que se intensifican las amenazas a los arrecifes, los grandes conjuntos de datos de acceso abierto son cada vez más esenciales para monitorear la salud de los arrecifes y predecir los impactos futuros.

Por lo tanto, CoralCT desempeña un papel importante en la preservación de valiosos registros del crecimiento de los corales y su historia medioambiental, a la vez que promueve el intercambio colaborativo, accesible y transparente de datos. Al poner la ciencia de los arrecifes de coral a disposición de investigadores y del público en general, conecta datos, ideas y personas para abordar cuestiones cruciales sobre nuestro mundo cambiante.

Agradecimientos

CoralCT se desarrolló con el apoyo de la subvención OCE-2444864 de la National Science Foundation. El uso de nombres comerciales, de empresas o de productos se realiza únicamente con fines descriptivos y no implica su respaldo por parte del gobierno de los Estados Unidos. Agradecemos al Equipo Científico de la Expedición IODP 389, al personal de apoyo del Operador Científico de ECORD (ESO), al equipo de perforación bentónica, a los topógrafos del MMA y al capitán y la tripulación del MMA Valour. La Expedición 389 del Programa Internacional de Ocean Discovery (IODP) contó con el apoyo financiero de las diversas agencias nacionales de financiación de los países participantes en el IODP. También agradecemos a todos los contribuyentes de datos hasta la fecha, entre ellos Giulia Braz, Jessica Carilli, Leticia Cavole, Ben Chomitz, Travis Courtney, Ian Enochs, Thomas Felis, Ke Lin, Malcolm McCulloch, Haojia Ren, Riccardo Rodolfo-Metalpa, Natan Pereira y al Programa de Recursos de Riesgos Costeros y Marinos del Servicio Geológico de los Estados Unidos.

Referencias

Barkley, H. C., et al. (2018), Repeat bleaching of a central Pacific coral reef over the past six decades (1960–2016), Commun. Biol., 1, 177, https://doi.org/10.1038/s42003-018-0183-7.

DeCarlo, T. M., et al. (2024), Calcification trends in long-lived corals across the Indo-Pacific during the industrial era, Commun. Earth Environ., 5, 756, https://doi.org/10.1038/s43247-024-01904-8.

DeCarlo, T. M., et al. (2025), CoralCT: A platform for transparent and collaborative analyses of growth parameters in coral skeletal cores, Limnol. Oceanogr. Methods, 23(2), 97–116, https://doi.org/10.1002/lom3.10661.

Hudson, J. H. (1981), Growth rates in Montastraea annularis: A record of environmental change in Key Largo Coral Reef Marine Sanctuary, Florida, Bull. Mar. Sci., 31(2), 444–459, www.ingentaconnect.com/content/umrsmas/bullmar/1981/00000031/00000002/art00014.

Hudson, J. H., et al. (1976), Sclerochronology: A tool for interpreting past environments, Geology, 4(6), 361–364, https://doi.org/10.1130/0091-7613(1976)4<361:SATFIP>2.0.CO;2.

Knutson, D. W., et al. (1972), Coral chronometers: Seasonal growth bands in reef corals, Science, 177(4045), 270–272, https://doi.org/10.1126/science.177.4045.270.

Lough, J. M. (2008), Coral calcification from skeletal records revisited, Mar. Ecol. Prog. Ser., 373, 257–264, https://doi.org/10.3354/meps07398.

Rodgers, K. S., et al. (2021), Rebounds, regresses, and recovery: A 15-year study of the coral reef community at Pila‘a, Kaua‘i after decades of natural and anthropogenic stress events, Mar. Pollut. Bull., 171, 112306, https://doi.org/10.1016/j.marpolbul.2021.112306.

Información de los autores

Avi Strange y Oliwia Jasnos, Universidad de Tulane, Nueva Orleans, Luisiana; Lauren T. Toth, Centro de Ciencias Costeras y Marinas de San Petersburgo, Servicio Geológico de Estados Unidos, Florida; Nancy G. Prouty, Centro de Ciencias Costeras y Marinas del Pacífico, Servicio Geológico de Estados Unidos, Santa Cruz, California; y Thomas M. DeCarlo (tdecarlo@tulane.edu), Universidad de Tulane, Nueva Orleans, Luisiana.

This translation by Daniela Navarro-Perez was made possible by a partnership with Planeteando and Geolatinas. Esta traducción fue posible gracias a una asociación con Planeteando y Geolatinas.

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