EOS

A major landslide has occurred in the vicinity of Altos de Oriente and Manantiales, near to Medellín and Bello, in Colombia. It is believed that about 25 people died.

On 24 June 2025 at 3:20 am, a large landslide occurred in the vicinity of Altos de Oriente and Manantiales, near to Granizal in Colombia. At the time of writing, 13 bodies have been recovered and a further 12 are missing. In total, 50 houses were destroyed.

I don’t yet have the precise location of this landslide tied down. A map on the El Colombiano news site places it at [6.30905, -75.53277], but this is yet to be confirmed.

There is very good aerial footage of it in a news report posted to Youtube by Cubrinet:-

At around 1 minute 45 seconds into this footage, this image is captured-

The 25 June 2025 landslide at Granizal in Colombia. Still from a video posted to Youtube by Cubrinet.

This image shows the crown of the landslide:-

The crown of the 25 June 2025 landslide at Granizal in Colombia. Still from a video posted to Youtube by Cubrinet.

The failure has occurred in deeply weathered regolith. It is a debris slide, with the main portion being comparatively deep-seated. It is notable that there is a considerable volume of water visible in the images:-

The upper portion of the 25 June 2025 landslide at Granizal in Colombia. Still from a video posted to Youtube by Cubrinet.

Some news sites note that a water pipe has ruptured in the landslide. The failure occurred during a period of very heavy rainfall – the El Colombiano site quotes a local resident as saying:-

“It was raining all day and all night. About 10:00 p.m. there was a downpour that cleared before 2:00 a.m. When it wasn’t even raining, we heard the noise and when we found out, we realized that the mountain had come and covered the entire neighborhood”.

Sometimes, a small failure associated with heavy rainfall can rupture a water pipe, which feeds water into the slope, triggering a much larger landslide.

Low down in the track of the landslide, it has spread and bifurcated, controlled by the topography:-

The main body of the 25 June 2025 landslide at Granizal in Colombia. Still from a video posted to Youtube by Cubrinet.

Thee are concerns about a further landslide at this site, imperiling the teams charged with recovering the victims.

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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.

Staff at the National Science Foundation (NSF) were notified on 25 June that the agency’s office space, located in Alexandria, Va., will be taken over by Department of Housing and Urban Development (HUD) staff, raising the question of where more than 1,800 NSF employees will work. 

One NSF employee told E&E News that they had “literally zero idea” the news was coming until word spread among staff the previous evening. Many NSF employees had relocated to Northern Virginia on short notice when return-to-work orders were issued in January. NSF only moved into the newly constructed building in 2017 from its prior location in Arlington, Va.

In front of a banner reading “The New Golden Age of HUD” at a 25 June press conference, HUD Secretary Scott Turner announced that a “staggered and thoughtful” relocation process would take place. The relocation will move forward “as quickly as possible,” Michael Peters, commissioner of the Public Buildings Service for the U.S. General Services Administration, said at the press conference.

On 24 June, Jesus Soriano, president of the American Federation of Government Employees (AGFE) Local 3403, a union representing NSF staff, sent an alert to union members informing them that “HUD will take over the NSF building” and that NSF had not been involved in the decision, according to E&E News.

Speakers at the press conference did not provide details about HUD’s plans for the space. In a statement, AGFE Local 3403 indicated that the union was told that plans would include an executive suite for Turner, the construction of a new executive dining room, exclusive use of one elevator for Turner, and a gym for Turner and his family.

 
Related

•  Press Conference: The New Golden Age of HUD
•  American Federation of Government Employees Local 3403 Statement
•  Science Agency Staff Brace for HQ Takeover
•  Get Involved: AGU Science Policy Action Center
 

“While Secretary Turner and his staff are busy enjoying private dining and a custom gym, NSF employees are being displaced with no plan, no communication, and no respect,” AGFE Local 3403 wrote in the statement.

Turner rebuked the idea that the move was about personal perks. “This is not about Scott Turner. I didn’t come to government to get nice things,” Turner said. “This is about the HUD employees.”

Turner added that unsafe working conditions at the current HUD office space in Washington, D.C. were the reason for the move. “I would hope that no leader in government or otherwise would expect staff to work in an atmosphere where the air quality is questionable, leaks are nearly unstoppable, and the HVAC is almost unworkable. It’s time for a change.”

Addressing the coming transition for NSF, Peters said, “We are going to continue to support the National Science Foundation as we support every agency across the federal government to identify space that allows them to continue to fulfill their mission.” 

In its statement, AGFE Local 3403 pointedly questioned the merit of the relocation plan: “At a time when they claim to be cutting government waste, it is unbelievable that government funding is being redirected to build a palace-like office for the Secretary of Housing and Urban Development. The hypocrisy is truly dumbfounding.”

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

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

In the Arctic, one of the primary paths for water to flow is along water tracks, stream-like features that fill with and route water when the soil above permafrost thaws in the summer. While these water tracks are important for water and nutrient movement, little is known about their formation and how they might change in the future.

A new study in Reviews of Geophysics explores our current understanding of water tracks and what aspects are still unclear. Here, we asked the authors to give an overview of water tracks, the leading theories about their formation, and what questions remain.

What are water tracks and where do they form?

Remote sensing image of tundra water tracks in northern Russia. Credit: Del Vecchio and Evans [2025], Figure 1a

Water tracks are stream-like features that concentrate water flow in cold places where the ground is frozen in the winter. Since frozen ground doesn’t let water soak in, any water from rain, melting snow, or ice ends up moving along the surface or just under the top layer when it thaws in the summer, like through moss or soil.

Interestingly, water tracks do not have a stream channel like a typical stream. You don’t need steep hills for water tracks to occur either; even a gentle slope is enough to get water moving. Water tracks are mostly found in places with permafrost including the Arctic, parts of Alaska, northern Canada, Siberia, and even Antarctica.

What roles do water tracks play in polar regions?

Water tracks move a surprising amount of water across frozen landscapes, especially in places with hills or gentle slopes. Because the water gets funneled into these narrow paths, it also brings along nutrients, making water tracks hotspots for plant growth and biological activity in otherwise cold and dry areas. You’ll often see greener, thicker vegetation in these zones, and they can be places where more carbon dioxide and methane are produced.

From a landscape perspective, they act like pseudo-channels for water, but interestingly, they don’t seem to carve out the land or move much sediment. However, that could change with climate shifts, and if these areas start eroding, it might reshape parts of the Arctic landscape in new ways.

How do scientists identify and monitor water tracks at different spatial scales?

Water tracks were first spotted from the air using aerial photos, and today we still rely heavily on remote sensing to study them. On the ground, scientists can look at vegetation changes, soil wetness, and evidence of surface water flow, but because water tracks can stretch for hundreds of meters, satellite and drone imagery are super helpful. They show up well in high-resolution images and in certain types of data, like infrared, because the plants growing on water tracks are greener and more productive. Tools like LiDAR can also help track changes in elevation, which is useful for spotting subtle shifts or erosion over time. While coarser satellites like Landsat might miss them, newer ones like Sentinel or PlanetScope can pick them up much more clearly.

Appalachian State University undergraduate students Noah Caldwell, Key Hatch, and Emma Ferm walk to collect water and soil samples from a water track on the North Slope of Alaska, USA in July 2023. Credit: Thomas Tobul

What are leading theories that describe how water tracks form?

In our literature review, most studies only consider their individual water tracks, so there weren’t really generalized models of water track formation out there before our review. But from literature and our own work, we noted two main theories: one theory is that they’re the result of thawing ground ice like ice wedges that create long, linear paths for water to flow. As the ice thaws, water keeps following that path, advecting heat which causes further thawing, reinforcing the track.

The other theory is a slightly different feedback mechanism: a dip or disturbance in the permafrost table, maybe from a snowdrift, vegetation, or other small indent, collects more water, which causes more thawing and even more water to flow there, creating a self-reinforcing loop. Both theories not only help explain how water tracks form, but also why they tend to show up in regular, repeating patterns across the landscape.

How is climate change expected to influence water tracks?

This is still a big unknown, but we’re starting to get some ideas. As permafrost landscapes warm, snow melts earlier and the ground thaws deeper, which could change how and where water flows. If water starts moving through deeper, less porous soil layers, it might cause erosion in places that used to be stable, turning soft, spongy mats into channels that cut into the ground. That could release stored sediment and carbon, and even shift how water tracks connect and drain the landscape. We are also seeing signs that water tracks are drying out or consolidating into fewer, deeper gullies, which could lead to even more dramatic changes over time.

How could water tracks be used to understand the hydrosphere on Mars?

Studying water tracks helps us think differently about how water might emerge and flow on other planets.

Scientists have long compared water tracks on Earth to the dark streaks seen on Martian slopes like recurring slope lineae (RSL), especially since both appear and change seasonally in cold, dry environments. Places like Antarctica and the Canadian Arctic often serve as analogs for Mars for geoscientists, where similar streaky patterns show up seasonally, which some researchers have called water tracks. While recent research suggests these Martian features might be caused by dust and wind rather than water, Earth’s water tracks still offer clues. They show that even in frozen conditions, water can move across the surface without leaving a noticeable fingerprint of erosion, which is something that might have happened on Mars in the past. So, studying water tracks helps us think differently about how water might emerge and flow on other planets, even if it doesn’t leave obvious signs behind.

What are some of the remaining questions where additional modeling, data, or research efforts are needed?

We’ve only studied a handful of water tracks in detail, so our understanding is based on a small slice of the Arctic. There’s a big need for more field data and better remote sensing to match the huge areas where water tracks actually exist. We also need more modeling to figure out what really drives their behavior and how that will change in a warmer climate, whether it’s snow, vegetation, or water flow. Questions like how water tracks “remember” past years, or how they evolve over time, are still wide open. So, more data and better models are key to unlocking how these features work and how they might change in the future.

—Joanmarie Del Vecchio (joanmarie@wm.edu, 0000-0003-3313-6097), College of William and Mary, United States; and Sarah G. Evans (0000-0001-5383-8382), Appalachian State University, United States

Editor’s Note: It is the policy of AGU Publications to invite the authors of articles published in Reviews of Geophysics to write a summary for Eos Editors’ Vox.

Citation: Del Vecchio, J., and S. G. Evans (2025), Water tracks: the veins of thawing landscapes, Eos, 106, https://doi.org/10.1029/2025EO255021. Published on 25 June 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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Source: AGU Advances

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

No se tienen registros suficientes en las bases de datos globales de los peligros meteorológicos extremos. Por ejemplo, los eventos donde las temperaturas son potencialmente mortales y que se ajustan a las normas climatológicas generalmente no son incluidos en los estudios de riesgos, y las inundaciones locales o regionales a menudo suelen pasar desapercibidas para los instrumentos satelitales.

En los últimos 20 años Texas ha experimentado una cantidad inusualmente alta de fenómenos climáticos extremos, incluyendo un incremento en inundaciones y olas de calor. Usando datos satelitales de fácil acceso de precipitación y temperatura tomados diariamente, Preisser y Passalacqua crearon una visión más amplia de los riesgos por inundaciones y olas de calor que han afectado al estado en los últimos años.

Al consultar los datos de precipitación del 2001 al 2020, los investigadores definieron como un evento de inundación peligrosa a aquellos que ocurren en promedio una vez cada dos años o más, lo que significa que un evento de esa magnitud ocurre en un área determinada con una frecuencia que no supera los dos años. Compararon sus resultados con los registrados en la Base de Datos de Eventos de Tormentas de la NOAA y la base de datos del Observatorio de Inundaciones de Dartmouth (DFO por sus siglas en inglés). Su análisis detectó tres veces más inundaciones que en la base de datos del DFO y se identificaron daños adicionales de $320 millones de dólares.

El equipo también amplió el análisis sobre el calor extremo. En muchos estudios previos sobre amenazas múltiples sólo se consideraron las olas de calor, donde las temperaturas superaron un percentil, como el 90 o el 95, durante tres días seguidos. Este estudio también consideró los periodos donde la temperatura de globo de bulbo húmedo (índice WBGT) supera un umbral de salud de 30°C, en lugar de un percentil determinado. Bajo esta definición, los científicos determinaron que, entre 2003 y 2020, Texas vivió 2,517 días con eventos peligrosos de calor, lo que equivale a casi el 40% de los días dentro de este periodo. Estos eventos afectaron un total de 253.2 millones de kilómetros cuadrados.

El estudio consideró como eventos de amenazas múltiples aquellos en los que coinciden inundaciones y episodios de calor extremo. Usando el método del intervalo de recurrencia promedio, junto con la definición más amplia de peligros, los investigadores encontraron que las zonas del estado con una alta concentración de poblaciones minoritarias estaban expuestas a un mayor riesgo ante este tipo de eventos multiriesgo. Esto sugiere que los métodos más antiguos pueden subestimar tanto la magnitud de los eventos de amenaza múltiple como el impacto desproporcionado en comunidades marginadas, de acuerdo con los investigadores. (AGU Advances, https://doi.org/10.1029/2025AV001667, 2025)

—Rebecca Owen (@beccapox.bsky.social), Escritora de ciencia

This translation by translator Oscar Uriel Soto was made possible by a partnership with Planeteando y GeoLatinas. Esta traducción fue posible gracias a una asociación con Planeteando and GeoLatinas.

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.

The Arctic is experiencing the most rapid climate change on Earth as average temperatures there rise up to 4 times faster than on the rest of the planet. Among the many environmental effects of this warming, the Arctic Ocean, critically, is moving toward a “blue” state, meaning it is increasingly becoming ice free during the summer months.

This shift raises significant concerns about the region’s future. Arctic Indigenous peoples, for instance, heavily rely on stable ice conditions for traditional hunting, fishing, and travel. As ice disappears, these activities become more dangerous or impossible, threatening food security, cultural practices, and the transmission of Traditional Knowledge. Global geopolitical and economic pressures will also rise as new shipping routes open, previously inaccessible resources become available for extraction, and international competition over these resources rises.

Currently, scientists struggle to predict how an ice-free Arctic will react to and amplify a warmer global climate.

Currently, however, scientists struggle to predict how an ice-free Arctic will react to and amplify a warmer global climate. The lack of clear climate projections for the region is largely due to a shortage of key geological data describing former climatic conditions and how the Arctic has responded to past changes, as well as to difficulties interpreting the records we do have. Making sense of these data is essential for understanding how the Arctic will evolve in the coming decades.

Deep-sea sediment cores provide some of the best available archives from the Arctic Ocean. These cores, drilled and collected from sites around the region, contain sediments deposited over hundreds of thousands of years that offer clues about past ocean temperatures, sea ice and ice sheets, and ocean circulation changes. To gain insights specifically into how the Arctic may respond to future warming—and the broader implications for the planet—scientists focus on past “greenhouse” states, when Earth’s climate was warmer than it is today, such as the Last Interglacial, about 130,000 years ago.

The German R/V Polarstern, shown here during an expedition into the central Arctic Ocean in 2015, has enabled the acquisition of numerous sediment cores that archive past Arctic climate changes. Credit: Alfred Wegener Institute/Mario Hoppmann, CC BY 4.0

However, reconstructing past warm climates from deep-sea core records is challenging, particularly because the chronology of Arctic Ocean sediments has been difficult to establish. The lack of biological remains and the dissolution of calcium carbonate in these sediments complicate efforts to determine their ages (i.e., their chronostratigraphy). Furthermore, the use of different dating methods and uncertainties about sedimentation rates have led to conflicting interpretations of core records and hindered the development of a solid timeline for Arctic climate history [e.g., Stein et al., 2025].

Recent advances in research have raised questions about the accuracy of prior published ages of Arctic Ocean sediments. These developments have also highlighted ongoing uncertainties and the need to understand the abilities and limitations of different dating tools. Without this understanding, it will be difficult to identify and detail past greenhouse climates with confidence, which in turn, will limit our ability to apply knowledge of these past conditions to inform climate models.

The Arctic Ocean Stratigraphic Toolbox

In fall 2024, more than 40 scientists gathered at the ArcSTRAT conference in Tromsø, Norway, to discuss the latest research and how available methods can best be used to develop a reliable chronostratigraphic framework, or age model, for Arctic sediments. Additional goals were to foster shared understanding of the region’s climate history and to improve our ability to provide accurate data to climate modelers.

A key challenge in studying Arctic paleoclimate is that oceanic sedimentation rates are typically low across the region.

A key challenge in studying Arctic paleoclimate is that oceanic sedimentation rates are typically low across the region. In fact, the central Arctic Ocean is one of the slowest accumulating marine sedimentary environments globally because of limited sediment sources and biological productivity, suppression of sediment transport by sea ice, and sediment trapping on broad circum-Arctic continental shelves.

The slow sediment accumulation results in thin sediment layers that can make it difficult to obtain clear chronological data. Dissolution of calcium carbonate from deposited sediments, which can occur where deep seawater is undersaturated with respect to the mineral, further reduces the possibility of finding datable microfossils in the sedimentary record.

In some areas, biostratigraphy (the distribution of ancient life in sedimentary rocks) and stable isotope geochronology (which compares ratios of nonradioactive isotopes of, e.g., carbon or oxygen) can be used to refine age models. In other areas, alternative methods are needed to provide age constraints. Such methods include magnetostratigraphy, which dates sediment layers by correlating their magnetism to the record of Earth’s magnetic field reversals; amino acid racemization, which measures the time-dependent breakdown of proteins in fossils too old for radiocarbon dating; luminescence dating, which measures radiation that builds up in materials as they age; and radionuclide dating.

Fig. 1. Age models of Arctic Ocean sediments can incorporate data from many analytical methods. The sediment core seen here (brown bands at far left) is from Lomonosov Ridge near the geographic North Pole. Photographs of the upper 4 meters of the core are shown beside microfossil (planktic foraminifera) abundance in blue and the concentration of the cosmogenically derived isotope beryllium-10 (10Be) in yellow [Spielhagen et al., 1997]. Increases in either parameter are commonly associated with past interglacials. The global benthic (deep-water) oxygen-18 curve (δ18O) shows the ratio of oxygen-18 to oxygen-16 over time [Lisiecki and Raymo, 2005], highlighting the timing of interglacial marine isotope stages (MIS; red numbers near bottom) over the past 1 million years. This curve is shown above the geomagnetic polarity timescale, which shows the most recent magnetic reversal—from the Matuyama epoch to the Brunhes epoch—at roughly 781,000 years ago. Two end member age models have been commonly applied in the past: a high sedimentation rate (SR) scenario and low sedimentation rate scenario. These models produce widely varying age estimates for the same sedimentary layer. Some of the key new data (in red) being used to evaluate the age model options come from advances in biostratigraphy (notably, the discovery of Pseudoemiliania lacunosa, a calcareous nanofossil that went extinct during MIS 12) [Razmjooei et al., 2023], radiometric dating of bulk sediments using the uranium decay series isotopes protactinium-231 (231Pa) and thorium-230 (230Th) [Hillaire-Marcel et al., 2017], and amino acid racemization measured in the fossilized shells of planktic and benthic foraminifera [West et al., 2023]. Click image for larger version.

Recent breakthroughs, particularly in applying radionuclide methods, have shown promise in improving the accuracy of Arctic Ocean sediment age models (Figure 1). For example, novel applications of uranium series isotopes (e.g., thorium-230 and protactinium-231) have been used to propose new age constraints for marine sediment sequences from important topographic regions, such as the Mendeleev-Alpha and Lomonosov Ridges, where low sedimentation and poor preservation of fossil material have hampered previous attempts to date these sequences [Hillaire-Marcel et al., 2017]. These isotopes decay predictably over time, allowing scientists to date past interglacial periods more confidently, including the Last Interglacial and others occurring around 200,000 years ago.

These new radionuclide-based age constraints are supported in part by recent applications of more traditional dating methods like biostratigraphy. Specifically, a newly revised Arctic sediment chronology for the late Pleistocene (400,000–10,000 years ago) established on the basis of analyses of calcareous nanoplankton, although not perfectly aligned, showed less uncertainty in the identification of interglacial periods in the central Arctic Ocean [Razmjooei et al., 2023]. Tracking changes in the concentration of cosmogenic radionuclides, like beryllium-10, in Arctic sediments has also provided new insights into the timing of interglacials [Spielhagen et al., 1997].

The Need for a Multimethod Approach

Some methods are better suited than others for studying sediments from given locations because environmental conditions across the Arctic differ.

The generally low sedimentation rates across the Arctic Ocean produce thin sediment layers that require precise sampling and, because not every dating method works well everywhere, careful selection of analytical methods. Some methods are better suited than others for studying sediments from given locations because environmental conditions across the Arctic differ, contributing to variable sedimentation rates, variable preservation of fossils, and disturbances like erosion and bioturbation (the reworking of sediment layers by living organisms).

Whereas relying on a single method to study sediments from across the Arctic Ocean may lead to inaccuracies and gaps in understanding, different methods can complement each other, providing a fuller, more robust picture of the past. Discussions during the ArcSTRAT conference highlighted the importance of using a multimethod approach, combining the various available stratigraphic and isotopic dating methods.

The challenge lies in carefully selecting appropriate methods to study cores from different regions to minimize errors and uncertainties and provide a reliable reconstruction of past Arctic environments. In areas where calcium carbonate is well preserved (e.g., topographic highs), for example, biostratigraphy and isotope geochronology are extremely useful. In areas where it is not (e.g., deep basins), litho- and magnetostratigraphy combined with radionuclide dating might be better options.

The past few decades have seen the development and application of a veritable toolbox of different techniques for dating Arctic Ocean sediments. These tools must now be integrated and applied to study newly collected sediment archives.

New Arctic Archives

Alongside methodological developments, new Arctic sediment cores have been retrieved recently, including during the International Ocean Discovery Program’s Expedition 403. In 2024, this campaign successfully drilled more than 5 kilometers of sediment cores from the Fram Strait west of Svalbard that offer a high-resolution record of past Arctic climates [Lucchi et al., 2024].

The scientific aim of this drilling was to better understand the ocean system and cryosphere during past warm intervals and how they relate to high insolation (exposure to sunlight) and atmospheric carbon dioxide levels. This information is essential for comprehending the climatic evolution of the Northern Hemisphere and the dynamics of ice sheets, sea ice, and ocean circulation. Data from these cores will be invaluable for studying the mechanisms that lead to ice-free Arctic summers and for understanding the effects of these conditions within and beyond the Arctic.

The Norwegian icebreaker R/V Kronprins Haakon sails in the Arctic Ocean. Credit: Dimitri Kalenitchenko, UiT The Arctic University of Norway

In 2025, the European Research Council’s (ERC) Synergy Grant–funded “Into The Blue” (i2B) Arctic expedition aboard R/V Kronprins Haakon will focus on recovering additional unique sediment archives from the central Arctic Ocean. The plan is to use a combination of classical and cutting-edge techniques to explore the Arctic’s climate history as completely as possible, matching the methods to the demands of each core. Together with stratigraphic methods, these techniques include analyses of molecular biomarkers, palynology (the study of preserved pollen grains and spores), ancient DNA, radionuclides, and stable isotopes to reconstruct past sea ice conditions, ocean heat transport, and cryosphere variability during warmer-than-present climate states such as the Last Interglacial.

A Promising Start to the Work Ahead

The ArcSTRAT conference made clear that the work ahead is challenging but promising. The outcomes and consensus about coordinating multimethod approaches will provide a crucial framework for analyzing new cores from the i2B expedition and, hopefully, additional future expeditions. The meeting also helped to establish a forum for continued collaboration and knowledge exchange among Arctic stratigraphy experts—an important step toward resolving continuing disparities among dating methods and developing a robust Arctic Ocean chronostratigraphy.

As the Arctic continues changing at an unprecedented rate and advancing toward blue summers, understanding its past is more critical than ever.

As the Arctic continues changing at an unprecedented rate and advancing toward blue summers, understanding its past is more critical than ever. By piecing together the climatic history of past greenhouse states, scientists are building the foundation for more accurate climate models, which are essential for informing accurate global climate assessments that, in turn, guide policy decisions in countries and communities around the world.

With ongoing advances in the toolbox of techniques for studying ocean sediment stratigraphy, as well as the collection of new sediment records, we will be better positioned to predict how the Arctic will respond to further warming and what the far-reaching consequences of this response will be.

Acknowledgments

We thank the participants in the 2024 ArcSTRAT conference in Tromsø, Norway, especially keynote speakers Ruediger Stein, Anne de Vernal, Renata Lucchi, Jutta Wollenburg, and Stijn De Schepper. The conference was funded by the Research Council of Norway, as well as by ERC through the Synergy Grant “i2B–Into The Blue” (grant 101118519).

References

Hillaire-Marcel, C., et al. (2017), A new chronology of late Quaternary sequences from the central Arctic Ocean based on “extinction ages” of their excesses in 231Pa and 230Th, Geochem. Geophys. Geosyst., 18(12), 4,573–4,585, https://doi.org/10.1002/2017GC007050.

Lisiecki, L. E., and M. E. Raymo (2005), A Pliocene‐Pleistocene stack of 57 globally distributed benthic δ18O records, Paleoceanography, 20(1), PA1003, https://doi.org/10.1029/2004PA001071.

Lucchi, R. G., et al. (2024), Expedition 403 preliminary report: Eastern Fram Strait paleo-archive, Int. Ocean Discovery Program, https://doi.org/10.14379/iodp.pr.403.2024.

Razmjooei, M. J., et al. (2023), Revision of the Quaternary calcareous nannofossil biochronology of Arctic Ocean sediments, Quat. Sci. Rev., 321, 108382, https://doi.org/10.1016/j.quascirev.2023.108382.

Spielhagen, R. F., et al. (1997), Arctic Ocean evidence for late Quaternary initiation of northern Eurasian ice sheets, Geology, 25(9), 783–786, https://doi.org/10.1130/0091-7613(1997)025%3C0783:AOEFLQ%3E2.3.CO;2.

Stein, R., et al. (2025), A 430 kyr record of ice-sheet dynamics and organic-carbon burial in the central Eurasian Arctic Ocean, Nat. Commun., 16, 3822, https://doi.org/10.1038/s41467-025-59112-7.

West, G., et al. (2023), Amino acid racemization in Neogloboquadrina pachyderma and Cibicidoides wuellerstorfi from the Arctic Ocean and its implications for age models, Geochronology, 5(1), 285–299, https://doi.org/10.5194/gchron-5-285-2023.

Author Information

Jochen Knies (Jochen.Knies@uit.no), UiT The Arctic University of Norway, Tromsø; Matt O’Regan, Stockholm University, Sweden; and Claude Hillaire Marcel, Université du Québec à Montréal, Montreal, Canada

Citation: Knies, J., M. O’Regan, and C. H. Marcel (2025), Finding consensus on Arctic Ocean climate history, Eos, 106, https://doi.org/10.1029/2025EO250230. Published on 25 June 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.

A significant landslide has destroyed a major bridge on the Xiarong Expressway in Guizhou, China.

On 24 June 2025, intense rainfall triggered a significant landslide at the site of the Houzihé Grand Bridge, which is a part of the Xiarong Expressway (a key road that is also known as Xiamen–Chengdu Expressway (route G76).

The landslide toppled the bridge carrying both sides of the highway. The driver of an articulated truck had a very lucky escape when his vehicle stopped with the cab over the chasm. He was rescued successfully.

The best image I have found of this event is on the website of CNR:-

The aftermath of the 24 June 2025 landslide at Houzihé Grand Bridge in Guizhou, China. Image from CNR.

The failure appears to have removed at least one column supporting the carriageway on each side. Note the red truck partially hanging over the void.

Reports suggest that the landslide occurred at 7:40 am, but that problems had been identified at 5:51 am and that traffic control had been put in place. If that is the case, I am a little unsure as to how the truck ended up in that position.

I believe that the location of this landslide is [26.0111, 108.1241]. This is a Google Earth image of the site, collected in March 2013:-

Google Earth image of the site of the 24 June 2025 landslide at Houzihé Grand Bridge in Guizhou, China.

It is interesting to note that the rear scarp of the landslide appears to coincide with the small road that cuts across the hillside. In 2013 it appears that there were no buildings at this location, but the image above shows that some have been built since. In terms of understanding the failure, I would be interested in determining whether there was a fill slope at this point and/or whether the area had a properly engineered drainage system.

This failure will ask serious questions about the safety of the highway. The piers of the viaduct look to have been extremely vulnerable to this type of failure. A quick scan of Google Earth suggests that this configuration may have been replicated elsewhere. Take a look at this image from Google Earth, for example, from 2020 (located at 26.0817, 107.9566]:-

Google Earth image of another site on the Xiarong Expressway in Guizhou, China.

This failure also highlights another key issue – the management of slopes close to, but not a part of, major infrastructure sites such as roads and railways.

This part of China is suffering intense rainfall at the moment, driving record floods along some of the local rivers. Over 80,000 people have been evacuated.

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Source: AGU Advances

In 2003, several states and environmental groups sued the U.S. EPA for violating the Clean Air Act by not regulating emissions from new vehicles.

When the case eventually reached the Supreme Court, a group of climate scientists contributed an amicus brief—a legal document in which a third party not directly involved in the case can offer testimony—sharing data demonstrating that rising global temperatures were directly caused by human activity. This led to the Supreme Court deciding that greenhouse gases did constitute pollutants under the Clean Air Act and, ultimately, to the EPA’s 2009 endangerment finding that greenhouse gas emissions endanger human health. The endangerment finding became the basis for governmental regulation of greenhouse gases. Sixteen years later, the Trump administration is poised to repeal it, along with other environmental protections.

In a new commentary, Saleska et al., the authors of the amicus brief, reflect on the brief and the damage the endangerment finding’s potential repeal could cause.

Today, many of the climate scientists’ concerns from the early 2000s have become reality, the authors say. The Earth’s 12 warmest years on record all occurred after 2009. The oceans are growing hotter and more acidic, and Arctic sea ice is retreating. Sea level rise is speeding up—from 2.1 millimeters per year between 1993 and 2003 to 4.3 millimeters per year between 2013 and 2023. Continued warming is also affecting human health. Direct heat-related deaths are on the rise, and so too are wildfires, precipitation extremes such as flooding and drought, climate-enabled spread of disease, and disruptions in agricultural productivity.

The amicus brief authors also note that attribution science, the field that links specific weather events to climate change, has advanced since 2009. Today, they are even more firm in their stance that climate change poses a serious threat to society.

A reversal of the endangerment finding would likely require a lengthy legal process and compelling evidence that climate change does not pose a risk to human health and well-being. But the possibility of a repeal implies a worrying lack of trust in the science and increasing politicalization surrounding climate issues, the authors say. If the role of climate science in policymaking is weakened, it will harm scientific progress and our national well-being, they warn. (AGU Advances, https://doi.org/10.1029/2025AV001808, 2025)

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

Citation: Owen, R. (2025), What’s changed—and what hasn’t—since the EPA’s endangerment finding, Eos, 106, https://doi.org/10.1029/2025EO250219. Published on 24 June 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.

Mars’s current atmosphere is downright tenuous—conferring less than 1% the pressure of Earth’s—but there’s good evidence that it was substantially thicker in the past. Researchers have now directly observed atoms escaping in a hitherto unobserved way.

That process, known as atmospheric sputtering, may have facilitated Mars’s transition from a watery planet to the arid world it is today, the team reported in Science Advances.

“I’ve been looking for this since I was a postdoc.”

Since the early 2010s, planetary scientist Shannon Curry at the University of Colorado Boulder has pored over data from Mars, looking for signs that the Red Planet’s atmosphere is eroding. It’s been a long journey, she said. “I’ve been looking for this since I was a postdoc.” Colleagues even took to ribbing Curry that her search might be folly. “Every year, I would run my code, and I would look for it,” she said. “We started joking that it was like a unicorn.”

But Curry, the principal investigator of NASA’s Mars Atmosphere and Volatile Evolution (MAVEN) mission, now has reason to celebrate: She and her colleagues believe they’ve finally captured the first direct observations of sputtering on Mars.

Escaping via Kicks

Planetary atmospheres are constantly changing; everything from solar eclipses to volcanic eruptions to fossil fuel burning can alter their composition, density, and structure. Atmospheres can also erode via several processes. One is photodissociation, in which photons break apart molecules, creating lighter constituents that can go on to escape. Sputtering is another. That process involves high-energy ions, accelerated by the Sun’s electric field, plowing through a planet’s upper atmosphere and colliding with neutral atoms. Those energetic kicks impart enough energy to the neutral particles that they go on to escape the planet’s gravitational field.

Sputtering plays only a minor role in the escape of Mars’s atmosphere today—the rate of sputtering is currently several orders of magnitude lower than that of photodissociation. “But we think, billions of years ago, it was the main driver of escape,” Curry said.

Thanks to nearly a decade’s worth of MAVEN observations, Curry and her collaborators had access to detailed records of the Sun’s electric field and neutral particles in Mars’s atmosphere. They focused on neutral argon, a heavy noble gas. It’s generally difficult to remove argon from the Martian atmosphere in other ways, said Manuel Scherf, an astrophysicist at the Space Research Institute at the Austrian Academy of Sciences in Graz, Austria, who was not involved in the research. “The only really efficient escape mechanism at the moment is sputtering.”

Follow the Darkness

“We have to get out of the sunlight in order to detect sputtering.”

The team used simulations of Mars’s atmosphere to home in on where they might find a signal of sputtering. Looking above an altitude of roughly 360 kilometers seemed to be key, the modeling revealed. The team furthermore knew that it was critical to look at the side of Mars pointing away from the Sun. That’s because photodissociation dominates during the day. “We have to get out of the sunlight in order to detect sputtering,” said Janet Luhmann, a space scientist at the University of California, Berkeley, and a member of the research team.

The researchers compared the abundances of argon in the Martian atmosphere in two altitude bins: 250–300 and 350–400 kilometers. They also compared periods during which the Sun’s electric field pointed either toward or away from Mars. Sputtering should preferentially occur in the higher-altitude bin when the Sun’s electric field points toward Mars—that’s when ions are accelerated toward the planet’s atmosphere. Indeed, Curry and her colleagues found statistically higher densities of argon in that group of data.

The team calculated that argon was being sputtered at a rate of about 1023 atoms per second. That might seem like a large number, but it’s actually about 100 times lower than the current rate of photodissociation, Luhmann said. But billions of years ago, the Sun’s electric field was likely far stronger than it is today, and sputtering rates could have been much higher, possibly being the dominant contributor to eroding Mars’s atmosphere.

Such a shift could help explain what happened to Mars’s water.

There’s copious evidence that liquid water once existed on the surface of Mars—river valleys, dried lake beds, and other water-carved features persist to this day. This means that Mars’s atmosphere must have once been thick enough to support liquid water. “You need that atmospheric pressure pushing down on water to make it a liquid,” Curry said. But the Red Planet today is an arid world devoid of visible water. Sputtering could explain, at least partially, how the loss of pressure occurred.

And because liquid water is intimately tied to our conception of life, these results have important meaning, Scherf said. “You cannot know whether life can exist somewhere if you don’t understand the atmosphere and how it behaves.”

Curry and her colleagues are hoping to use MAVEN data for years to come, but the team recently learned that they may not have that opportunity: The mission is slated to be canceled in the proposed 2026 federal budget. That’s been a huge blow emotionally, said Curry, but the team isn’t giving up yet. “The United States right now is number one in Mars exploration,” Curry said. “We will lose that if we cancel these assets.”

—Katherine Kornei (@KatherineKornei), Science Writer

Citation: Kornei, K. (2025), Scientists spot sputtering on Mars, Eos, 106, https://doi.org/10.1029/2025EO250231. Published on 24 June 2025. Text © 2025. The authors. 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 that impacts science and scientists.

Astronomy is a field of temporal extremes. Some phenomena—the birth of stars, the ballet of galaxies within clusters, the growth of the Universe—take place over millions or billions of years, timescales too vast for the human mind to easily comprehend. Other events can happen in quick bursts that take you by surprise: Asteroids and comets flash by, a star goes supernova, pulsar beams sweep past at dizzying speeds, an exoplanet whips around a star in just a few hours.

The Vera C. Rubin Observatory is designed to watch it all.

The telescope, funded by the National Science Foundation and U.S. Department of Energy, has been 3 decades in the making, and it just released its first science images. Taken by a digital camera the size of a car in just over 10 hours of test observations, these images captured millions of galaxies and Milky Way stars and thousands of solar system asteroids.

The first look is…wow. Just wow. Take a look:

• This image of the Trifid and Lagoon Nebulas combines 678 separate images taken in just over 7 hours of observing time. Combining many images in this way clearly reveals otherwise faint or invisible details, such as the clouds of gas and dust that comprise the Trifid nebula (top right) and the Lagoon nebula (center), which are several thousand light-years away from Earth. Credit: NSF-DOE Vera C. Rubin Observatory
• This image shows a small section of Rubin’s total view of the Virgo galaxy cluster. Bright stars in the Milky Way galaxy shine in the foreground, and many distant galaxies are in the background. Credit: NSF-DOE Vera C. Rubin Observatory
• This image shows a small section of the Virgo galaxy cluster. Visible are two prominent spiral galaxies (lower right), three merging galaxies (upper right), several groups of distant galaxies, many stars in the Milky Way galaxy and more. Credit: NSF-DOE Vera C. Rubin Observatory

Named after pioneering dark matter astronomer Vera C. Rubin, the telescope has a 10-year primary mission during which it will create a wide-frame, ultra-high definition time-lapse record of the Universe.

 
Related

•  Vera C. Rubin Observatory
•  When a Telescope Is a National-Security Risk
•  Vera Rubin’s Legacy Lives On in a Troubled Scientific Landscape
 

From its perch atop Cerro Pachón in Chile, it will take thousands of images of the Southern Hemisphere sky every night and map the trajectories of millions of asteroids, comets, and interstellar objects in the solar system, enhancing planetary defense efforts. It will record the locations, distances, and brightness changes in distant supernovae, allowing for more precise calculations of the expansion rate of the Universe and deepening our understanding of mysterious dark matter and dark energy. And it might even help conclusively determine whether, and where, a large planet lurks in the far reaches of our own solar system.

And that’s just what we expect to see. Most scientists would say that the most exciting discoveries are the ones that they never even thought of before, the “unknown unknowns.” Humanity has never had a telescope quite like this one, and gosh, we just can’t wait to see what amazing discoveries are just around the corner!

The telescope sits inside the closed dome of the NSF-DOE Vera C. Rubin Observatory. NSF-DOE Vera C. Rubin Observatory, CC BY 4.0 International

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

These updates are made possible through information from the scientific community. Do you have a story idea about science or scientists? Send us a tip at eos@agu.org. Text © 2025. AGU. CC BY-NC-ND 3.0
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Boots On the Ground

“There’s no roads, there’s no helicopters, there’s not even a donkey.”

It’s just another day in the field.

The spartan accommodations available to scientists tracking Uganda’s dwindling glaciers is not universal to geoscience fieldwork, but they’re a good indication of the lengths to which scientists will go—enthusiastically—to discover and document our planet’s particularities. Read all about it in “A New 3D Map Shows Precipitous Decline of Ugandan Glaciers.”

Volcanologists on La Palma, the largest of the Canary Islands, faced a different challenge during their work in the field: an actively erupting volcano. In “Volcanic Anatomy, Mapped as It Erupts,” Vittorio Zanon and Luca D’Auria share how near-real-time petrological analyses can help support the safety of surrounding communities as well as associated scientific efforts.

Scientists on an Antarctic research cruise found themselves stymied by sea ice. But when a Chicago-sized ice shelf unexpectedly calved, the crew quickly pivoted and discovered a surprisingly “Thriving Antarctic Ecosystem Revealed by a Departing Iceberg.”

Far from being stranded, scientists “Tracking Some of the World’s Fiercest Ocean Currents” around the Mozambique Channel found that the eddy-ring dipoles there transport nutrients and biota at a rate of 1.3 meters per second.

Hazards like volcanoes, ice shelves, and ocean currents may ultimately be no match for the “looming catastrophes—funding cuts, software obsolescence, and loss of community support,” however. To this end, the data scientist–authors of “The Valuable, Vulnerable, Long Tail of Earth Science Databases” share research-based recommendations for supporting expert community-curated data resources.

Geoscience fieldwork is globe-spanning and mind-bending, and we hope you enjoy the ride.

—Caryl-Sue Micalizio, Editor in Chief

Citation: Micalizio, C.-S. (2025), Worldwide fieldwork, Eos, 106, https://doi.org/10.1029/2025EO250220. Published on 23 June 2025. Text © 2025. The authors. CC BY-NC-ND 3.0
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Source: Space Weather

The impacts of space weather such as extreme solar winds and magnetic waves are not limited to outer space. Bursts of plasma emanating from the Sun, for instance, can temporarily intensify electric and magnetic fields on the ground when they arrive at Earth, causing geomagnetically induced currents (GICs) to flow into infrastructure such as powerlines, pipelines, and railways. GICs can cause widespread equipment failures, leading to blackouts and safety concerns.

To improve monitoring, modeling, and forecasting of GICs in the United Kingdom, Beggan et al. developed a set of 14 models that better predicts space weather hazards and tracks them in real time, allowing scientists and forecasters to warn operators of critical infrastructure. They also installed three new variometers to measure magnetic field changes at locations across the country. The work was part of the United Kingdom’s Space Weather Instrumentation, Measurement, Modelling and Risk (SWIMMR) program called SWIMMR Activities in Ground Effects, or SAGE.

The SAGE system can estimate changes in the subsurface electric field during geomagnetic storms, then calculate the size of GICs flowing into grounded infrastructure networks—which have known electrical resistance properties—in real time. SAGE also uses real-time data from satellites to predict the probability of magnetic substorms occurring and the magnitude of the storm at different U.K. ground observatory sites.

A major test of the new system occurred in early May 2024, when significant solar activity triggered the largest geomagnetic storm to hit Earth in the past 30 years. SAGE successfully provided real-time information on how the storm was affecting infrastructure. The system also provided two forecasts of GIC magnitude 30 minutes ahead of time; the real-time magnitude that SAGE later identified was between those two predictions.

More work must be done to continue improving SAGE, the authors write. For example, better monitoring of space weather conditions in space and on the ground would provide the system with more robust data on impacts, further improving its prediction capability. (Space Weather, https://doi.org/10.1029/2025SW004364, 2025)

—Saima May Sidik (@saimamay.bsky.social), Science Writer

Citation: Sidik, S. M. (2025), U.K. space weather prediction system goes operational, Eos, 106, https://doi.org/10.1029/2025EO250229. Published on 23 June 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.

27 people were killed by a massive channelised debris flow in China last year.

On 3 August 2024, a large debris flow occurred in the Ridi valley, Kangding, Sichuan Province, China. This event is described in a paper (Cheng et al. 2025) just published in the journal Landslides. Whilst the paper itself is behind a paywall, this link should provide access to it.

This event is a really good example of a phenomenon that keeps cropping up, namely multiple shallow landslides that transition into a highly destructive channelised debris flow, generated by extremely intense rainfall. The value of the Ridi valley example is that Cheng et al.(2025) have forensically investigated this particular event.

The outlet of the Ridi valley is located at [30.069422, 102.105085]. This is a Google Earth image of the site from September 2022:-

Google Earth image of the Ridi valley from September 2022.

This is quite remarkable terrain – the linear distance from the top of the catchment to the main channel is about 9.5 km, but the elevation difference is over 4,000 metres. Thus, the catchment is exceptionally steep. Debris flows have been recorded in the Ridi valley in 1952, 1963, 1966, and 1982. Note the large fan at the junction with the maion channel, which is populated and is crossed by a key road (China National Expressway G4218).

I have downloaded a Planet Labs image of the site from 1 August 2024 and draped it onto the Google Earth DEM:-

Satellite image of the Ridi valley before the 3 August 2024 landslides ad debris flow. Image copyright Planet Labs draped onto the Google Earth DEM, used with permission. Image dated 1 August 2024

And here is a Planet Labs image from 5 August of the site, showing the aftermath of the landslides and debris flow:-

Satellite image of the Ridi valley after the 3 August 2024 landslides ad debris flow. Image copyright Planet Labs, draped onto the Google Earth DEM, used with permission. Image dated 5 August 2024.

And here is an image compare:-

Images copyright Planet Labs.

The Planet Labs images show multiple shallow landslides in the catchment and also the track of the debris flow. Cheng et al.( 2025) have mapped 28 shallow landslides and four rock slope collapses in the catchment. These had a total volume of about 12,000 cubic metres. It is fascinating to note that the local rain gauges did not record any substantial rainfall at the time of the event, suggesting that the trigger was a highly localised rainstorm.

The initial 12,000 m3 of landslide material combined to form a debris flow that eroded a further 31,000 m3 from the slopes below, and 337,000 m3 from the channel to form a debris flow with a total volume of 380,000 m3. Thus, the initial slope failures constituted just 3.2% of the total debris flow volume. This is the epitome of a cascading event.

Cheng et al.( 2025) do not document the detailed impact of the 2024 Ridi valley debris flow, saying just that “the disaster had severe impacts on local residents and infrastructure.” The Planet Labs image suggests that this might have been very severe:-

Satellite image of the Ridi valley after the 3 August 2024 landslides ad debris flow. Image copyright Planet, draped onto the Google Earth DEM, used with permission. Image dated 5 August 2024.

A news report at the time indicated that up to 27 people were killed. Xinhua published this image of the impact on Ridi:-

The aftermath of the 3 August 2025 debris flow in the Ridi valley. Image published by Xinhua.

Reference

Cheng, Q., Liu, T., Lei, H. et al. 2025. Investigation of a shallow high-locality landslide-induced debris flow in an alpine valley: A case study of the Ridi debris flow, Kangding, Sichuan Province, China (August 3, 2024). Landslides. https://doi.org/10.1007/s10346-025-02559-y

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

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Source: Journal of Geophysical Research: Planets

Like Earth, Mars is surrounded by an ionosphere—the part of its upper atmosphere where radiation from the Sun knocks electrons off of atoms and molecules, creating charged particles. The Martian ionosphere is complex and continuously changes over the course of the day, but its role in atmospheric dynamics and radio communication signals means understanding it is key for Mars exploration.

One way to study the Martian ionosphere is with radio occultation, in which a spacecraft orbiting Mars sends a radio signal to a receiver on Earth. When it skims across the Martian ionosphere, the signal bends slightly. Researchers can measure this refraction to learn about Martian ionospheric properties such as electron density and temperature. However, the relative positions of Mars, Earth, and the Sun mean conventional radio occultation cannot measure the middle of the Martian day.

Now, Parrot et al. deepen our understanding of the Martian ionosphere using an approach called mutual radio occultation, in which the radio signal is sent not from an orbiter to Earth but between two Mars orbiters. As one orbiter rises or sets behind Mars from the other’s perspective, the signal passes through the ionosphere and refracts according to the ionosphere’s properties.

The researchers analyzed 71 mutual radio occultation measurements between two European Space Agency satellites orbiting Mars: Mars Express and the ExoMars Trace Gas Orbiter. Thirty-five of these measurements were taken closer to midday than was ever previously achievable, in effect allowing scientists to see a new part of the Martian ionosphere.

The new data enabled the research team to calculate how the ionosphere’s electron density changes throughout the day. They were also able to learn more about how the altitudes of the upper and lower layers of the ionosphere—called M2 and M1, respectively—vary daily. The new data suggest that the peak electron density of the M2 layer changes less dramatically during the day than has been suggested by prior research. The data also show that the M1 does, indeed, still exist during the midday, contradicting previous assumptions.

The researchers also used the new data to calculate ionospheric temperatures. They found that instead of being hottest at midday, temperatures in the ionosphere rise as the Sun reaches Martian sunset. Simulations using a Mars climate model suggest that it is likely winds transporting air, rather than the Sun’s direct heat, that control these temperature dynamics. (Journal of Geophysical Research: Planets, https://doi.org/10.1029/2024JE008854, 2025)

—Sarah Stanley, Science Writer

Citation: Stanley, S. (2025), Orbiter pair expands view of Martian ionosphere, Eos, 106, https://doi.org/10.1029/2025EO250228. Published on 20 June 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.

Coral reefs are vital ecosystems supporting marine life, ecotourism, and coastal protection. They also hold something valuable under their surface: records of the ocean’s past. Beneath the living outer layer of massive corals are dense, rocklike skeletal structures containing annual bands, similar to tree rings. Scientists can study the conditions at the time these bands formed by drilling, retrieving, and analyzing cores, some of which represent centuries of coral growth.

Daren Coker (left) and Thomas DeCarlo drill for a coral core in the Red Sea. Credit: Morgan Bennett-Smith

Since the 1970s, studies of coral cores to determine past growth patterns, a field known as coral sclerochronology, have produced notable scientific discoveries. Knutson et al. [1972] found that annual bands comprise alternating high- and low-density bands that reflect seasonal growth patterns. Hudson [1981] found that typically, high-density bands form during slower winter growth and low-density bands form during faster summer growth and that long-term coral growth variations are influenced by water quality and the effects of coastal development. Some cores also contain high-density “stress bands” formed because of coral bleaching events or other environmental challenges [Lough, 2008]. Together, this banding provides insights into coral growth history, enabling scientists to construct reliable age models of past oceanic and climatic conditions.

Today, methods used to investigate coral cores have advanced considerably. Alongside other methods such as stable isotope and elemental ratio analyses, computed tomography (CT) scanning plays a major role in yielding data that help to reveal coral growth parameters. Scientists can use 2D X-ray and 3D CT scanning to examine the internal structure of coral cores, including their annual density bands [Knutson et al., 1972; Hudson, 1981; Lough, 2008; DeCarlo et al., 2025]. In some cases, such analysis even involves a scientist visiting a local hospital to use its CT machine—an unexpected patient for the radiology technician.

This animation of a CT scan shows a cross section of a coral core. The small circles within the core are corallites, the individual skeletal structures formed by coral polyps. Credit: USGS, Public Domain A coral core sits on the exam table of a CT machine at a hospital before being scanned. Credit: Thomas DeCarlo

However, there has been no systematic archiving of coral core imagery data, partly because of the lack of a suitable repository. This gap presents risks of losing valuable images and prevents streamlined, transparent sharing of scientific interpretations from these images. Therefore, a centralized, virtual, open-access repository of coral core imagery is crucial for fostering transparent science and preserving these resources for future research.

An App for Organizing an Archive

The CoralCT application was developed to consolidate and organize coral core scans in a virtual repository that enables digital archiving and image analysis [DeCarlo et al., 2025]. The repository currently contains scans of more than 1,000 cores collected from a wide range of coral reef regions, including the Great Barrier Reef, the Caribbean, and the Red Sea. These core scans have been contributed by individuals and agencies, including the U.S. Geological Survey (USGS) and NOAA.

Coral researchers upload X-ray or CT scans to CoralCT and, when they are ready, can make their data publicly available to anyone with a computer and internet connection. This approach to transparency fosters collaborations among coral core researchers, who can view the app’s core directory and see who else has collected cores from their areas of interest. It also helps avoid unnecessary duplication of research efforts, which is especially important given the need to reduce sampling impacts on corals, many of which are endangered species.

Using the application’s analytical tools, observers can map annual density bands in coral cores to extract data on growth rates and skeletal density. As in tree ring studies, this sort of analysis offers insights into past environmental conditions because coral growth can respond sensitively to climate variability.

For example, Barkley et al. [2018] used CoralCT to visualize high-density stress bands and reconstruct the history of coral bleaching over 6 decades on a remote reef in the equatorial Pacific Ocean where monitoring data were sparse. Rodgers et al. [2021] measured annual growth rates in CoralCT to track the recovery of corals off Kaua‘i, Hawaii, in the 15 years after a damaging flood event. More recently, DeCarlo et al. [2024] leveraged the breadth of cores in CoralCT to reconstruct coral growth trends over recent decades to centuries across thousands of kilometers of the Indo-Pacific.

Rescuing Old Records and Gathering New Ones

Archiving valuable data that might otherwise be lost is a foundational purpose of CoralCT. A standout example of how it’s serving this purpose involves the rescue and digitization of X-ray images of more than 20 cores collected across the Pacific Ocean between the 1980s and early 2000s. The X-ray films, previously stored by a retiring scientist, are now archived and available for analysis on CoralCT.

Older collections like these can provide valuable insights into coral growth before environmental disturbances, such as mass bleaching from heat stress, began to affect them.

In a similar effort, USGS recently CT scanned coral cores dating back to the late 1960s, some of the earliest cores ever collected [Hudson et al., 1976]. These scans are being added to the repository so they can be reanalyzed by researchers now and into the future. Older collections like these can provide valuable insights into coral growth before environmental disturbances, such as mass bleaching from heat stress, began to affect them.

Alongside these historical contributions, CoralCT’s repository continues to grow with the addition of new data. One such recent contribution includes scans of reef cores collected from offshore Hawai‘i in 2023 during the International Ocean Discovery Program’s Expedition 389. Reef cores differ from coral cores in composition and structure but are also critical for understanding ocean history and environmental change. During Expedition 389, cores were collected from drowned reefs that once grew near the ocean surface but stopped calcifying as they were submerged in deeper water. These reef cores contain fragmented coral, coralline algae, microbialites, and other reef-building materials whose compositions enable scientists to look millennia into the past and uncover valuable records of sea level and climate change.

Repeatable Analyses, Verifiable Results

When raw, unprocessed coral core images are not archived, the value of growth measurements and other analyses is limited because other scientists cannot readily and independently verify them. This is problematic because science fundamentally relies on the ability to repeat experiments and verify results, especially considering individual researchers can introduce subjectivity and potential biases into even highly systematic and rigorous interpretations of data. As datasets grow larger, more intricate, and more numerous, maintaining transparency is increasingly important but also increasingly difficult.

In this screenshot of a coral core being analyzed in the CoralCT application, the orange lines on the core image indicate where an observer has mapped the annual density bands. Credit: Avi Strange

CoralCT addresses these challenges by ensuring that all information and context about a core is fully documented, accessible, and downloadable. This information includes essential metadata such as the core’s origin, ownership details, collection date, depth, and species identifications. Most important, CoralCT archives the user-defined maps of annual banding used to derive growth rate data [DeCarlo et al., 2025], ensuring that these data and interpretations are fully reproducible and open to verification by others.

This transparency is also shared among observers within the application. When a user is mapping the bands of a core, they can add notes and screenshots that other users can view when they’re analyzing that core. Furthermore, when a user finishes mapping the bands of a core and processes the data, this information is saved and made downloadable for other scientists to view. This ability enables scientists to conduct multiobserver studies, which can reduce potential biases introduced by individual observation.

A challenge encountered in our efforts to broaden CoralCT has been the hesitancy of some researchers and programs to share data.

Despite these advantages, a challenge encountered in our efforts to broaden CoralCT has been the hesitancy of some researchers and programs to share data because of concerns about intellectual property infringements and the “scooping” of prepublication data. This hesitancy, which is understandable considering the lack of transparency and protections for data owners in prior data management practices, can unfortunately limit scientific advancements and collaborations that might help address climate change, coral reef degradation, and other complex challenges.

To address these concerns, CoralCT offers privacy controls to core owners that they can use to restrict access to their scans and the derived output data. These controls are particularly useful when cores are part of ongoing research that has not yet been published or are subject to a postcruise moratorium, ensuring that sensitive data remain protected until the research is ready to be shared. In addition, each core is tagged with a data owner, acknowledgments, and relevant citations.

Advancing Accessibility and Collaboration

CoralCT also represents a path to making science more inclusive and accessible. The application is designed with an easy-to-use interface and includes resources such as video tutorials and a step-by-step user guide to help introduce its features to a wide audience. K–12 lesson plans that guide students through mapping coral core bands in the app were also recently created, offering approachable ways to explore marine science.

A middle school student visiting the Sclerochronology Lab at Tulane University uses a virtual reality headset to interact with coral cores in 3D during the university’s 2025 Boys at Tulane in STEM event. Credit: Danielle Scanlon Middle school students learn about coral cores from a hologram at a workshop at Hawai‘i Pacific University. Credit: Thomas DeCarlo

The app’s educational potential was demonstrated during recent outreach events. Using virtual reality technology, middle school students in New Orleans viewed 3D coral core scans from CoralCT and practiced identifying annual density bands. At a similar event, sixth grade students in Hawaii interacted with 3D holographic coral cores, learning how scientists retrieve and study them to understand growth patterns over time. The positive experiences of students and teachers during these events demonstrated how CoralCT provides an opportunity to engage hands-on with real scientific data.

Integration of AI could also, importantly, make it easier for all users to contribute to coral core analysis, regardless of their academic background or field experience.

Looking forward, there is potential to integrate artificial intelligence (AI) into CoralCT for automated identification of coral banding patterns. If an AI system were trained on existing human interpretations, it could automatically suggest band markings that users could review and verify. This advancement offers the potential for more accurate and efficient coral core analyses while maintaining human oversight. Integration of AI could also, importantly, make it easier for all users to contribute to coral core analysis, regardless of their academic background or field experience. Each new contribution or analysis of a core enhances the CoralCT database and extends our knowledge of coral reefs and past ocean conditions.

Coral sclerochronology is vital for understanding environmental changes in coral reef ecosystems and the impacts these changes have wrought. Through this research, we gain insights into the ocean’s past and advance our understanding of coral reefs today. As threats to reefs intensify, large open-access datasets are increasingly essential for monitoring reef health and predicting future impacts.

CoralCT thus plays an important role in preserving valuable records of coral growth and environmental history while promoting collaborative, accessible, and transparent data sharing. In making coral reef science available to researchers and the public alike, it is connecting data, ideas, and people to address critical questions about our changing world.

Acknowledgments

CoralCT was developed with support from National Science Foundation award OCE-2444864. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. government. We thank the IODP 389 Expedition Science Party, ECORD Science Operator (ESO) support staff, benthic drilling team, MMA surveyors, and the captain and crew of the MMA Valour. International Ocean Discovery Program (IODP) Expedition 389 was supported by funding from the various national funding agencies of the participating IODP countries. We also thank all data contributors to date, including 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, and the U.S. Geological Survey Coastal and Marine Hazards Resources Program.

References

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.

Author Information

Avi Strange and Oliwia Jasnos, Tulane University, New Orleans, La.; Lauren T. Toth, St. Petersburg Coastal and Marine Science Center, U.S. Geological Survey, Fla.; Nancy G. Prouty, Pacific Coastal and Marine Science Center, U.S. Geological Survey, Santa Cruz, Calif.; and Thomas M. DeCarlo (tdecarlo@tulane.edu), Tulane University, New Orleans, La.

Citation: Strange, A., O. Jasnos, L. T. Toth, N. G. Prouty, and T. M. DeCarlo (2025), A coral core archive designed for transparency and accessibility, Eos, 106, https://doi.org/10.1029/2025EO250226. Published on 20 June 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.

A community in China had a narrow escape when a landslide, triggered by Typhoon Wutip, occurred on the slopes above the village. Fortunately, the population had been evacuated when a local woman noted signs that a failure might be imminent.

At about 4 am on 15 June 2025, rainfall associated with the remnants of Typhoon Wutip triggered a landslide at Zhonghe village in western Guangdong province in China. At present I am unable to give a precise location for this event, which is listed in the Chinese media as having occurred at Lian’er Natural Village, Zhonghe village, located in Guizi Town, Xinyi City, Maoming. Guizi town is located at [22.6397, 111.1113], so it is in this general area.

China Daily has a photographic feature on this landslide, which includes this image:-

The 15 June 2025 landslide at Zhonghe village in western Guangdong province, China. Image via China Daily.

There is also a view from the crown of the failure looking along the landslide track:-

View from the crown of the 15 June 2025 landslide at Zhonghe village in western Guangdong province, China. Image via China Daily.

This failure affected 25 households and 57 people, but all were evacuated in the hours prior to the event (see below). The landslide itself appears to have been a large, shallow failure that has channelised before striking the village. Note also at least two other shallow failures in the same area – these landslides are characteristic of landslides triggered by very high rainfall intensities that drive saturation and a loss of suction forces.

It is fortunate that the material involved in the failure was comparatively fine-grained, which has meant that the damage to the village appears to be modest. XKB has this image of the aftermath of the landslide:-

The aftermath of the 15 June 2025 landslide at Zhonghe village in western Guangdong province, China. Image via XKB.

There is an article in nfnews (in Mandarin) that describes the sequence of events that led to the evacuation of the community. The key person is Liu Mingfang, a member of the Zhonghe Village Committee. This is a description of the events (using Google Translate):-

In the rain, her vision was blurred, and Liu Mingfang used a flashlight to patrol along the muddy village road. At 0:42 on the 15th, she suddenly discovered: “Why is this water yellow and muddy, and it still carries sediment?”

Red flags! She immediately dialed the phone number of Cao Musheng, the village party secretary: “Secretary, there is an abnormality in the water, something may happen!” ”

In less than 5 minutes, Liu Chunhua and Cao Musheng, deputy mayors of the village, arrived at the scene. After research and judgment, Liu Chunhua decisively reported to the town’s three prevention offices and received instructions: transfer immediately!

At 0:58, a total of 10 village cadres and village cadres rushed from all directions to the entrance of Lian’er Natural Village. Immediately afterwards, the sound of gongs, knocks on the door, and shouts instantly tore apart the rainy night.

The entire community was relocated before the slope failed.

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Boreal peatlands in Canada provide crucial ecosystem services, from flood mitigation and water purification to storing colossal amounts of carbon and providing a habitat for species such as caribou.

Over the past several decades, more than 36,000 hectares of well pads have been constructed to house oil and gas drilling platforms in these landscapes, destroying the underlying vegetation and disrupting the flow of water through the ground.

“We want to get as close to the original state as is possible and realistic.”

Once drilling operations are finished, operators are required to return pads to a state similar to that before construction. Though restoration efforts have historically focused on tree planting, reintroducing the right mosses is crucial for restoring functional peatlands. A study in Ecological Engineering outlines a new approach to reintroduce these keystone plant species, tested for the first time at the scale of a full well pad in Alberta, Canada.

“We want to get as close to the original state as is possible and realistic, given the very long time scales that peatlands develop over,” said Murdoch McKinnon, a graduate student at the University of Waterloo and lead author of the study.

The challenge is providing the right hydrological conditions for mosses to thrive.

Removing Fill

Well pads are constructed by heaping crushed mineral fill onto a section of peat to create a harder level surface.

Traditionally, researchers in the region have reintroduced moss by first completely removing the fill, which lowers the surface so that it is closer to the water table. In some cases, they would bury some of the fill under the newly exposed peat, a technique referred to as inversion.

This process has been successful in establishing the Sphagnum mosses typical of bogs, which have acidic soil that is low in nutrients. It’s been less successful in reintroducing the Bryopsida mosses characteristic of fens, the nutrient-rich wetlands that make up almost two thirds of peatlands in Canada’s Western Boreal Plain.

“I think it’s a good approach, but maybe the surface of the pad was not low enough to have flowing water, which you need in a fen.”

To reestablish a moss community that could eventually turn into a fen, the team left some of the fill on the surface, which provided the minerals that Bryopsida mosses rely on for growth. The team then roughed up the surface with an excavator to create different microsites, which promotes species diversity.

After introducing mosses from a nearby donor fen and closely monitoring the site for two growing seasons, researchers found that conditions for the reestablishment of Bryopsida mosses were best when the water table was within 6 centimeters (2 inches) of the surface. That was often the case along the edges of the pad that received water from the adjacent peatland, whereas the mosses in the interior of the pad struggled with drier conditions.

“I think it’s a good approach, but maybe the surface of the pad was not low enough to have flowing water, which you need in a fen,” said Line Rochefort, an expert in peatland restoration at Université Laval in Quebec who was not involved in the study.

“Without addressing that, it’s hard to introduce and establish peatland vegetation on mineral substrate,” said Bin Xu, a peatland ecologist at the Northern Alberta Institute of Technology (NAIT) who worked on the project. “On the flip side, when you do have good hydrobiological conditions, it’s really easy to support peat-forming vegetation, which is encouraging.”

A well pad located near the town of Slave Lake, Alberta, was still brown immediately after researchers introduced the moss, before it started to become established. Credit: University of Waterloo

An important takeaway from the study is the importance of decompacting the surface by roughing it up to allow for not only hydrological flow across the pad but also the natural vertical fluctuation of the water table, Xu said.

He and colleagues at NAIT have now applied these lessons to three additional well pads in Alberta, and industry experts have used a similar approach on around a dozen more, Xu said. “Through informing policy and sharing the learnings with industry, we can together address the need to reclaim well pads built in peatland across the province.”

—Kaja Šeruga, Science Writer

Citation: Šeruga, K. (2025), Surface conditions affect how mosses take to former well pads in Canada’s boreal fens, Eos, 106, https://doi.org/10.1029/2025EO250227. Published on 18 June 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: Journal of Geophysical Research: Oceans

Submarine canyons around Antarctica tend to have less sea ice, higher sea surface temperatures, and more biomass such as phytoplankton blooms than the shelves they cut into. Phytoplankton blooms feed Antarctic krill, making these canyons an attractive feeding ground for larger predators such as penguins, who make permanent homes for foraging and breeding on the shores surrounding submarine canyons.

Previous studies suggested that, as on a farm, the phytoplankton blooms that attract predators were locally grown, supported by the upwelling of nutrient-rich water. But newer research shows that water moves through the canyon more quickly than phytoplankton can accumulate, so it is likely that currents transport most of the surface biomass into the canyon from other parts of the ocean. Canyons therefore act more like biomass supermarkets, to which food is delivered, than like farms.

McKee et al. examined to what degree phytoplankton grow locally in Palmer Deep canyon on the western Antarctic Peninsula versus being transported in by ocean currents. To do so, they used high-frequency radar to measure ocean currents and satellite imagery taken hours to days apart to measure levels of surface chlorophyll, a proxy for phytoplankton.

The results showed that both processes were occurring. Ocean currents appeared to bring in much of the phytoplankton that flowed on the western side of the canyon, making it more like a supermarket, the researchers write. In contrast, more phytoplankton seem to be growing in place on the eastern flank, making it more like a farm.

The authors also examined how the movement of water correlated to plankton growth, by tracking chlorophyll levels in moving parcels of water. In general, they found that water parcels that saw an increase in phytoplankton levels as they moved through the canyon tended to exhibit more clockwise motion, whereas parcels that saw decreasing phytoplankton levels showed more counterclockwise rotation. (Journal of Geophysical Research: Oceans, https://doi.org/10.1029/2024JC022101, 2025)

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

Citation: Owen, R. (2025), Where do Antarctic submarine canyons get their marine life?, Eos, 106, https://doi.org/10.1029/2025EO250224. Published on 18 June 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.

Derek Cronmiller of the Yukon Geological Survey has provided a stunning set of the images of the fascinating recent failure that partially blocked the Yukon River.

Following my post yesterday about the May 2025 landslide on the Yukon River, Derek Cronmiller, who is head of Surficial Geology at the Yukon Geological Survey kindly made contact to provide further information about this most interesting failure. He has also provided an amazing set of images of the landslide.

Derek noted the following about the landslide:-

“The slide is a 9 km above Lake Laberge and happed sometime between May 14th and 18th as constrained by Sentinel imagery and river user reports.“

“The slide is 950 m wide and up to 250m long from crown to toe. It blocked ~ 45% of the active channel which is no small feat on the Yukon River! The material is finely bedded glaciolacustrine silt and clay at river level (and below) grading up to massive medium to coarse sand at the top of the main scarp with variable thickness of aeolian dune cover at the surface.  Perhaps the most interesting part of the slide is that the rupture surface daylighted somewhere in the river and thrust river bottom sediments (and vegetation) several metres above the river level. There are some great spreading structures on the slide reminiscent of sensitive clay slides in Quebec. We observed seeps daylighting at the bottom of the adjacent slopes just above river level at the transition from sands to silt and clay. Slides have occurred here in the past but an order of magnitude smaller.”

And so to the images. This image shows the landslide from a drone, looking from the crown towards the river:-

The May 2025 Yukon River landslide, viewed from a drone. Image copyright the Yukon Geological Survey, used with permission.

The very beautiful morphology of this landslide is visible with rows of back-tilted trees, with upright trees in between. Note also the uplifted toe of the landslide, including river gravels.

Let’s take a look at the toe – here is the uplifted portion, located almost half way across the former channel. The scale of the uplift here is really impressive:-

The uplifted toe of the May 2025 Yukon River landslide. Image copyright the Yukon Geological Survey, used with permission.

For those who are unfamilar with rational landslides, and who may be wondering how this is possible, I provided a sketch of this mechanism back in 2013 at the time of the Hatfield Stainforth landslide:-

Sketch of the rotational landslide mechanism of the 2013 Hatfield Stainforth landslide. The Yukon River landslide had a similar mechanism.

This rotational generates some complex structures in the landslide, including horst and graben phenomenon:-

Horst and graben structures in the toe of the May 2025 Yukon River landslide. Image copyright the Yukon Geological Survey, used with permission.

And this image shows the uplifted river gravels in more detail:-

Uplifted river gravels in the toe of the May 2025 Yukon River landslide. Image copyright the Yukon Geological Survey, used with permission.

Moving up into the main body of the landslide, there are some extremely impressive back-tilted blocks:-

Back-tilted blocks in the May 2025 Yukon River landslide. Image copyright the Yukon Geological Survey, used with permission.

And also some horst and graben structures:-

Back-tilted trees in the May 2025 Yukon River landslide. Image copyright the Yukon Geological Survey, used with permission.

Finally, there are areas of seepage as Derek noted above, which probably gives an indication of one of the drivers of this landslide:-

Seepage in the May 2025 Yukon River landslide. Image copyright the Yukon Geological Survey, used with permission.

This is a really interesting landslide – in many ways, a textbook example of a complex rotational failure. If I was still teaching, I would use this landslide to illustrate the mechanisms of rotational landslides.

Many thanks to Derek Cronmiller and his colleagues at the Yukon Geological Survey for providing these amazing images and the detailed commentary. I hope that they will write the landslide up for publication in due course.

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Source: Radio Science

Between 50 and 1,000 kilometers above our heads is the ionosphere, a layer of Earth’s upper atmosphere consisting of charged particles: ions (atoms that have gained or lost a negatively charged electron) and loose electrons. The ionosphere alters the path of electromagnetic waves that reach it, including radio and GPS signals, so studying it is helpful for understanding communication and navigation systems.

One way to study the ionosphere is to “nudge” it with powerful radio waves sent from the ground to see how it reacts. Where the waves hit the ionosphere, they temporarily heat it, changing the density of charged particles into irregular patterns that can be detected from the way they scatter radio signals. By studying these irregularities, known as artificial periodic inhomogeneities (APIs), scientists can learn more about the ionosphere’s composition and behavior.

However, factors such as space weather and solar activity can inhibit both the formation and detection of APIs. La Rosa and Hysell sought to enhance the reliability and utility of the API research technique by examining API formation in all three main regions of the ionosphere, the D, E, and F regions. Past techniques focused only on API formation in the E region.

To do so, the researchers revisited data from research conducted in April 2014 at the High-frequency Active Auroral Research Program (HAARP) facility in Alaska. HAARP’s radio transmitters created small perturbations in the ionosphere, and the facility’s receivers captured the resulting scattered radio signals.

Initial analysis of the 2014 data revealed some APIs in the E region, but this team of researchers reprocessed the data at higher resolution. This reanalysis allowed them to document, for the first time, simultaneous APIs across all three regions, all triggered by a single radio nudge.

API formation in each of the three regions is dictated by a different set of mechanisms, including chemical interactions, heating effects, and forces that change the density of charged particles; this variability has made it difficult to develop a stand-alone model of API formation across the ionosphere.

To address that challenge, the researchers extended a model previously created to capture API formation in the E region by incorporating the relevant mechanisms for the D and F regions. In simulation tests, the model successfully reproduced the behavior observed in all three regions. This model could help deepen understanding of the physics at play in the ionosphere. (Radio Science, https://doi.org/10.1029/2025RS008226, 2025)

—Sarah Stanley, Science Writer

Citation: Stanley, S. (2025), Nudging Earth’s ionosphere helps us learn more about it, Eos, 106, https://doi.org/10.1029/2025EO250222. Published on 17 June 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: Geochemistry, Geophysics, Geosystems

Geologists are responding to increasing demand for a variety of rare metals by focusing attention on the origins of high silica leucogranites that often host high concentrations of valuable metals such as niobium (Nb), tantalum (Ta), zirconium (Zr), hafnium (Hf), tin (Sn), and lanthanides. Many of these rocks have anomalous trace-element signatures (distinctively low ratios of Zr/Hf, Nb/Ta, and europium (Eu)/(gadolinium (Gd) + samarium (Sm)) that have long been thought to indicate extensive fractional crystallization or interaction with large volumes of fluid. They may also have unradiogenic Hf isotope ratios suggestive of input from depleted mantle sources despite their presence in thick crustal orogenic belts.

Huang et al. [2025] contribute measurements of the stable isotope ratio of boron (B) and the radiogenic neodymium (Nd) system from a belt of Paleozoic leucogranites in the Qilian orogenic belt in central China. The results show decoupling of Nd and Hf isotope signatures, not consistent with simple crust/mantle mixing, but correlation of Hf and B isotope signatures with trace element ratios that fingerprint mixing of various sedimentary rocks in the sources of the granites. The authors conclude that these are pure S-type (sediment-derived) magmas, whose budget of valuable metals was scavenged from the Paleozoic crust rather than concentrated by extreme fractionation of mantle-derived magma, overturning the common interpretation based on Hf isotope data alone. 

Citation: Huang, H., Niu, Y., Romer, R. L., Zhang, Y., He, M., & Li, W. (2025). High silica leucogranites result from sedimentary rock melting—Evidence from trace elements and Nd-Hf-B isotopes. Geochemistry, Geophysics, Geosystems, 26, e2024GC012024. https://doi.org/10.1029/2024GC012024

—Paul Asimow, Editor, G-Cubed

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