A major slope failure killed many people, possibly over 300, in an area of unlicenced mining of the mineral Coltan.

On 19 June 2025, a very significant landslide occurred at the Rubaya mining site in Masisi territory, North Kivu, which is located in the eastern part of the Democratic Republic of the Congo (DRC). The landslide, which reportedly affected a place called Bibatama, killed at least 21 people, but in all probability many more people died. Local news site Mines.cd reports over 300 fatalities.

The Rubaya mining area is a large, unlicenced and unregulated shallow excavation for the extraction of Coltan (known industrially as tantalite), an ore from which niobium and tantalum are extracted. The primary use of tantalum is in mobile phones, but it is also used in computer hard drives and road vehicle electronics.

These types of disastrous mining landslides in less developed countries rarely attract much interest (imagine what would have happened if this event had occurred in Canada or Australia), so I decided to see whether I could find anything out about it. I must note that landslides at this site are common – for example, about 100 people were killed in a landslide in 2013.

The Rubaya mining area is well covered in Google Earth – this is an image from 2021. The marker gives the general location – we’ll come back to this spot below:-

Zoom in and you find a landscape scarred by shallow workings and landslides:-

The Rubaya mining area has a very challenging history. In recent years, possession has alternated between the military and various militias, who have run the site as a protection racket. Since April 2024, the site has been controlled by the March 23 Movement (M23), a rebel group with a long history of human rights violations.

I have been trying to use Planet Labs images to try to identify the location of the 19 June 2025 landslide. I think the most likely location is in the mining area located at [-1.58203, 28.89378]:-

This mining area has expanded rapidly in recent years. The 2021 Google Earth image shows that it has been subject to a number of landslides.

I have downloaded a Planet Labs image from 14 June 2025 – five days before the landslide, and I have draped onto the Google Earth DEM. Of course, the Planet Labs imagery has a lower spatial resolution than the Google Earth imagery:-

The image shows a higher level of mining activity than was the case in 2021, and possibly some further landslides. By comparison, the image below was captured on 25 June 2025, after the landslide:-

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

I think the landslide is visible on the left side of the mining area. A series of shallow workings have been destroyed, and the track and runout zone of the landslidecan be seen. The feature that is probably the landslide is about 250 metres long.

These types of landslides in unlicenced and unregulated mining sites are a major contributor to global landslide fatalities, but they are rarely investigated.

Finally, in an interesting twist, the FT reported last week that an ally of Donald Trump, Gentry Beach, is seeking to “snap up” the Rubaya mine site.

Reference

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

Text © 2023. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

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

Source: Water Resources Research

One of the challenges in global hydrology is to simulate water resources globally at a resolution that is fine enough to be of local relevance. However, these hyper-resolution (less than 1 kilometer) simulations are limited by the very high computational demand of routing water through the global river system.

Shrestha et al. [2025] devise a very clever upscaling algorithm for stream directions that allows simulating streamflow at low-resolution, while still being able to locally refine ate points of interest, such as locations where streamflow is measured. This computational breakthrough opens the door to very detailed global hydrological simulations, not only for global hydrology, but for Earth system science at large.

Citation: Shrestha, P. K., Samaniego, L., Rakovec, O., Kumar, R., & Thober, S. (2025). A novel stream network upscaling scheme for accurate local streamflow simulations in gridded global hydrological models. Water Resources Research, 61, e2024WR038183.  https://doi.org/10.1029/2024WR038183  

—Marc F. P. Bierkens, Editor, Water Resources Research

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.

If astronomers have learned one lesson from 6,000 or so confirmed exoplanets, it’s to expect the unexpected. Even so, a giant planet orbiting a red dwarf star recently caught them by surprise. It is the largest planet relative to its host star yet discovered, and it defies the leading theory of giant-planet formation, according to a new study.

TOI-6894 b orbits an M dwarf star roughly one fifth the size and mass of the Sun—60% the mass of the next-smallest star with a giant planet. TOI-6894 b is the size of Saturn and half its mass. The planet is 40% the diameter of the host star, making it by far the highest planet-star size ratio yet seen.

“Because the star is so low mass, based on what we currently understand about planet formation and protoplanetary disks, we wouldn’t have expected it to be able to form a gas-giant planet,” said Edward Bryant, an astrophysicist at the University of Warwick in the U.K. and first author of the study, published in Nature Astronomy.

The planet was first detected by the Transiting Exoplanet Survey Satellite (TESS) in early 2020 and confirmed with additional observations over the following 3 years. TESS looks for the dip in a star’s brightness that occurs when a planet passes between it and Earth, blocking some of its light.

Bryant and his colleagues scoured observations of 91,000 stars in the TESS catalog to determine the frequency of giant planets around low-mass red dwarfs, which are the smallest and faintest stars in the galaxy and the most common. They reported the discovery of several such planets in 2023.

The team’s new analysis shows that the transits of TOI-6894 b are record breakers, reducing the star’s brightness by 17% and hinting at how large the planet is relative to its star. The transits also show that it orbits every 3.37 days.

The follow-up observations with ground-based telescopes measured changes in the star’s radial velocity—back-and-forth “wobbles” in its motion caused by the planet’s gravitational pull that revealed the planet’s mass.

A Special Case?

The leading theory of giant planet formation, called core accretion, posits that such worlds form early in a star’s lifetime, when it is still encircled by a protoplanetary disk—a wide disk of gas and dust that comprises the raw building materials for planets. Heavier materials coalesce to form larger and larger bodies, eventually creating a core that can be several times the mass of Earth. When the core grows large enough, it gobbles up the surrounding gas, building a layered giant planet similar to Saturn or Jupiter.

“The total amount of heavy material in the disk determines how big of a core you can make,” said Joel Hartman, a research astronomer at Princeton University and a member of the study team. “It’s a surprise to find a giant planet around such a tiny star because we just didn’t think there would be enough material there.” Some studies, he added, have suggested that stars less than about one third the mass of the Sun should not be able to form giant planets at all.

“Theorists who model planet formation [with core accretion] are not able to create planets like TOI-6894 b,” said Emily Pass, an astrophysicist at the Massachusetts Institute of Technology who was not involved in the study. “So the question becomes, Are planets like TOI-6894 b special cases that formed in a different way, or does our entire model of giant planet formation need a revision?” Pass explained. “Understanding the occurrence rate of [such] planets will help test the various possibilities.”

Hinting at the Formation Mechanism

One possibility is a modified accretion mechanism, in which the growing planet hoovers up both heavy materials and gas simultaneously, forming a more mixed world.

Another possibility is direct collapse. “Instead of the core being built from the ground up, the disk fragments under its own self-gravity and directly collapses,” Bryant said. “If the disk becomes unstable in the right way, you can form giant planets around these low-mass stars. The problem is that some of the simulations predict that you would only form planets that are much, much more massive than Jupiter, which would be many times more massive than this planet. So none of these theories can really explain this planet. We’re really limited by our understanding of protoplanetary disks,” he said.

Hints of the planet’s formation mechanism may be found in its atmosphere, which is scheduled for study in the next year by the James Webb Space Telescope (JWST). As the planet passes in front of the star, starlight shining through the atmosphere will reveal its composition.

“We should be able to tell the difference in whether a planet formed from direct collapse versus core accretion by looking at the atmosphere’s metallicity,” which is the makeup of elements heavier than hydrogen and helium, Hartman said. “In the gravitational instability case, all the materials collapsed together, so the elements should all be mixed together. In the core accretion model, all the heavy elements should be in the core, with a gaseous envelope on top of it.”

Because of the large transit signal, TOI-6894 b should be “amenable” to additional ground-based studies, Hartman said, although none are currently planned. “We’ll wait and see what JWST tells us,” Bryant said.

—Damond Benningfield, Science Writer

Citation: Benningfield, D. (2025), A new exoplanet resets the scale, Eos, 106, https://doi.org/10.1029/2025EO250235. Published on 30 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.

An excellent new paper (Walden et al. 2025) examines the occurrence of accelerated movement in rock slope landslides in Alaska as adjacent glaciers melt.

The exceptional temperatures in recent days in both North America and Europe has once again highlighted the rate at which the climate is changing in response to anthropogenic increases in greenhouse gases. In most glaciated areas, retreat of the large ice masses is occurring. There has long been discussion of how the slopes adjacent to glaciers will respond to these changes.

There is a very good new open access paper (Walden et al. 2025) in the journal Natural Hazards and Earth System Sciences that examines this issue for eight landslides in southern coastal Alaska. These are large, rock slope failures in areas in which the adjacent glaciers are retreating rapidly. In some cases, the glacier has already retreated beyond the slope, leaving it bordering lakes or fjords. In other cases, the slope is still in contact with the ice, which is in retreat.

On of these landslides is at the actively retreating Barry Glacier – this is a very large rock slope failure, with an estimated volume of between 188 and 500 million cubic metres. This is a Google Earth image of the site in 1996:-

And this is the same site in 2019:-

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

The change in the glacier is, of course, startling, but the large rock slope landslide is also notable.

Walden et al. (2025) have used archive datasets extending back to the 1980s to examine these eight slopes as the glaciers below them changed. They found that six of the slopes have experienced a period of substantially increased rates of movement. In four sites, a pronounced acceleration was observed as the terminus of the glacier retreated past the landslide area. Two other sites showed rapid movement during a period of wet weather or as the glacier rapidly thinned. In two cases, the sites did not appear to undergo a change in behaviour.

This is illustrated by data from the Barry Glacier site. This is a part of Figure 4 from Walden et al. (2025), showing the measured landslide velocity (upper graph), the retreat of the terminus of the glacier (middle graph) and the change in thickness of the Barry glacier (lower graph). The pink shading shows onset of rapid movement. The slope underwent a really rapid phase of movement (over 20 metres per year) as the adjacent glacier thinned and the slope started to debuttress.

Large rock slopes are incredibly complex, and the ways in which they interact with their environment (including an adjacent glacier, but also rainfall, seismic forcing and suchlike) is also complex, so we would not expect them all to respond in the same way. But this study is important for two reasons.

First, it provides additional support for the notion that glacial debuttressing is an important element of the geomorphology of areas undergoing glacial retreat.

But second, large rock slope failures can be very hazardous, either through direct impact from the resulting rock avalanche or as a result of the generation of a localised displacement wave. This study once again highlights the need to monitor these types of slope better, to undertake hazard analyses and to ensure that local populations are prepared for the consequences of a rapid collapse event.

Reference

Walden, J., Jacquemart, M., Higman, B., Hugonnet, R., Manconi, A., and Farinotti, D. 2025. Landslide activation during deglaciation in a fjord-dominated landscape: observations from southern Alaska (1984–2022), Natural Hazards and Earth System Sciences, 25, 2045–2073, https://doi.org/10.5194/nhess-25-2045-2025.

Text © 2023. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

The morning of 23 July 2024 was like most summer mornings in Yellowstone National Park. Cars vied for parking spaces, bison lounged in meadows, and tourists strolled along boardwalks taking in sights of bubbling springs and spouting plumes of water and steam. All were unaware of the pressure that had built underneath Black Diamond Pool, a thermal spring in Wyoming’s Biscuit Basin about 3.5 kilometers northwest of famed Old Faithful Geyser.

Suddenly, just before 10:00 a.m., jets of muddy, rock-laden water and steam shot from the turbid depths of the pool, building into bursts as high as 400–600 feet (~120–180 meters) that showered the surrounding area and boardwalk with rocks and mud. Water from the pool surged toward the nearby Firehole River, carrying boulders and debris, and a steam plume was visible from kilometers away.

Fifty-five seconds after the explosion began, it was over. Left behind was a roughly 1-square-kilometer debris field, as well as many stunned onlookers, fresh from scrambling away from the unexpected outburst and wondering what had just happened.

Safety was the paramount concern in the immediate aftermath of the event. But scientists also mobilized quickly to monitor for additional activity and to collect timely observations that could help piece together why the explosion happened. On a longer timescale, federal, state, and academic organizations are working together to better understand the dynamics and triggers of hydrothermal explosions to recognize warning signs of future events before they occur.

What Are Hydrothermal Explosions?

Hydrothermal explosions, like the July 2024 event at Black Diamond Pool (Figure 1), occur in many volcanic-hydrothermal areas around the world. When a pressurized hot water reservoir instantaneously decompresses, superheated water violently flashes to steam that has enough energy to break surrounding rock [Muffler et al., 1971; Thiéry and Mercury, 2009; Browne and Lawless, 2001; Montanaro et al., 2022].

Such explosions exist on a continuum from large, destructive events to smaller geyser eruptions that routinely spew water and steam into the air. Geysers are caused by constrictions in hydrothermal plumbing systems that temporarily trap boiling water and steam until the pressure is high enough for the water to erupt. Hydrothermal explosions, on the other hand, occur less frequently. They are primed by the gradual pressure increase in a confined system, followed by rapid decompression caused either by rupturing of a hydrothermal seal or by an external event like a landslide or earthquake. Large geyser eruptions can destroy geysers’ plumbing systems and throw rock and mud like hydrothermal explosions, and small, spontaneously reoccurring hydrothermal explosions may arguably be more consistent with geyser activity.

In Yellowstone National Park, the occurrence of hydrothermal explosions has been recognized for decades. Since the end of the most recent glaciation roughly 14,000 years ago, at least 18 massive hydrothermal explosions have formed craters ranging from 300 to 2,500 meters across, the largest of which—formed about 13,800 years ago—is the biggest explosion crater on Earth [Muffler et al., 1971; Morgan et al., 2009; Christiansen et al., 2007].

More than 2 dozen hydrothermal explosions have been documented within Yellowstone National Park since its founding in 1872 [Christiansen et al., 2007]. One of the best-observed events prior to 2024 was the explosion of Porkchop Geyser in Norris Geyser Basin on 5 September 1989 [Fournier et al., 1991]. That event—witnessed by nine people, none of whom were injured—threw small rocks and debris 60 meters from the vent and left a crater more than 10 meters wide.

Smaller hydrothermal explosions occur more frequently than larger ones (maybe as often as annually), but they usually go unwitnessed because they occur in the backcountry, at night, or during winter months. Hydrothermally active areas around the world sometimes show signs of instability or increases in temperature prior to an explosion; however, there are no known universal precursory signals upon which forecasts can be based.

Keeping Watch over Yellowstone’s Activity

The lack of knowledge about hydrothermal explosion occurrence rates, precursory signals, and triggers motivated the Yellowstone Volcano Observatory (YVO), a consortium of nine federal, state, and academic organizations, to include hydrothermal processes and hazards in its recently developed hazards monitoring plan [Yellowstone Volcano Observatory, 2022]. The plan includes the installation of broadband seismic, infrasound, thermal, and deformation sensors within geyser basins to better detect anomalous hydrothermal activity and investigate the potential to forecast hazardous events.

A prototype hydrothermal monitoring station, installed in Norris Geyser Basin in 2023, immediately paid dividends. The station clearly detected infrasound signals from nearby geyser eruptions and a small hydrothermal explosion that occurred on 15 April 2024—the first hydrothermal explosion in Yellowstone National Park to be documented by instrumental monitoring [Poland et al., 2025].

However, no hydrothermal monitoring station was installed at Biscuit Basin in July 2024, and YVO’s volcano monitoring network barely detected the explosion, even though it was big enough to destroy a section of boardwalk adjacent to Black Diamond Pool. The destructive event—thankfully, no injuries resulted—emphasizes the importance of expanded monitoring in geyser basins of Yellowstone National Park. It also highlights the risk posed by even small explosions that occur when people are nearby.

Much remains unknown about the processes leading to hydrothermal explosions and how best to safeguard the more than 4 million visitors to Yellowstone National Park every year from this underappreciated hazard [e.g., Montanaro et al., 2022]. The goal of postexplosion scientific investigations is to develop understanding that will enable better monitoring, detection, and, potentially, forecasting of future dangerous hydrothermal events.

Black Diamond Pool’s Explosive Past and Present

Explosive activity has recurred sporadically at Black Diamond Pool over its roughly 120-year life. Broken, angular rocks from previous explosions that were cemented back together before being ejected on 23 July 2024 provide evidence of this repeated explosive activity.

According to early geologic maps and photographs, Black Diamond Pool did not exist before 1902. It likely formed dramatically from a hydrothermal explosion sometime between then and 1912. Documents preserved in the Yellowstone National Park archives reference a few short periods of explosive activity that enlarged the new pool and formed two additional springs.

The area was quiet after 1960 until a series of short explosive events of varying intensity (though none approaching the scale of the July 2024 event) reinitiated in 2006. The frequent activity ceased by early 2013, and only three isolated events were reported between then and July 2024.

The 23 July hydrothermal explosion—which occurred during the park’s busiest month—stunned tourists, National Park Service (NPS) officials, and the scientific community. Visitation numbers had peaked a few days earlier, and on the day of the explosion, cameras recorded 209 visitors to Biscuit Basin by 9:00 a.m. Within minutes of the approximately 10:00 a.m. event, law enforcement rangers arrived on the scene and quickly closed the basin to the public to prevent injuries should explosive activity continue.

YVO’s initial response primarily involved communicating to the public and emergency managers about the cause of the event and the potential for additional activity. Observatory scientists also fielded numerous media inquiries.

Coordination of the scientific response began in parallel with these communications activities. YVO scientists and experienced collaborators from other institutions deployed to the field within hours to days to install monitoring equipment and gather time-sensitive data using a variety of approaches.

Fanning Out in Biscuit Basin

Working near an unstable, potentially explosive pool in the immediate aftermath of the explosion was an exercise in situational awareness, but the extensive training and experience of the scientists involved helped to ensure their safety.

Field teams worked in pairs, with one person keeping an eye out for signs of an ensuing explosion while the other collected data. High-temperature areas surrounding the pool suggested the presence of boiling water or steam underneath a thin crust where the ground could easily collapse or another explosion could break out. Near the pool edge, slippery mud and overhangs that could crumble unexpectedly into the pool also posed particular hazards.

The field teams also knew that newly unsealed hydrothermal systems can emit higher-than-normal amounts of hazardous gases. Thankfully, blowing winds following the explosion diluted potentially dangerous concentrations as well as the strong perfume of acid, sulfur, and hydrocarbons, helping the teams get on with their work.

Geology and Mapping. Hydrothermal explosions leave behind debris fields that can be used to discern many properties of the explosions [Breard et al., 2014]. For example, the size and distribution of ballistic blocks around the vent provide clues about the energy of the explosion. This information also enables calculations of ballistic vulnerability—the probability of a human fatality at any given location around the vent in the event of another explosion of similar size. In addition, rocks excavated from the preexisting subsurface hydrothermal system are useful for understanding the pressure and temperature conditions before the explosion and how sealed the system was.

Field teams from Colorado State University, NPS, and the University of California, Berkeley documented the sizes, distribution, and lithology of ballistic blocks thrown by the explosion to begin piecing together what the underlying hydrothermal system looked like before and during the explosion. NPS also used an uncrewed aerial vehicle to collect thermal and structure-from-motion imagery of the deposits and the surrounding area. These images helped identify areas with elevated temperatures and quantify the volume of material ejected by the 23 July explosion.

Near-Surface Geophysics. Dense seismic networks, which can sense the vibrations of bubbles and the brecciation of rock, are powerful tools for resolving subsurface hydrothermal plumbing, detecting small explosions, and helping scientists assess hazards from ongoing activity.

To record seismic signals in the aftermath of the explosion at Black Diamond Pool, the University of Utah deployed a temporary array of 33 seismometers around the pool by 26 July, and the instruments recorded for about 2 months. Four infrasound microphones were also deployed roughly 300 meters northwest of the pool from 19 August to 18 October. These data will be processed to pinpoint and explore signals from geyser activity and subsequent small hydrothermal explosions in Biscuit Basin.

Several weeks after the explosion, field teams from the University of Wyoming and NPS collected nuclear magnetic resonance (NMR), electrical resistivity (ER), and transient electromagnetics (TEM) datasets. NMR data provide estimates of the volume and location of water stored in the subsurface, including in confining, low-permeability zones. ER, which measures resistivity encountered by electrical currents, is ideal for identifying water-saturated subsurface pathways, as hydrothermal waters contain dissolved salts and are electrically conductive. TEM uses pulses of electric current to induce electric and magnetic fields underground. How fast these fields decay is another indication of variations in subsurface resistivity.

Together these techniques paint 3D views of hydrothermal fluids and lithological contrasts in the subsurface—important information for understanding the conditions and characterizing hazard potential in the postexplosion Black Diamond Pool system.

Water and Gas Chemistry. Gas emissions and water chemistry data were collected after the 23 July explosion by the U.S. Geological Survey (USGS), Montana Technological University, and the University of Wyoming to help probe underground processes.

Gridded measurements of carbon dioxide gas efflux, for example, provide information on spatial variations in diffuse gas fluxes at the surface that can be used to map subsurface gas pathways. Simultaneous measurements of isotopes of the short-lived radioactive gas radon in the same samples used for carbon dioxide measurements can help identify the sources of emissions and timescales of gas movement.

The chemical composition of the water in Black Diamond Pool is important because the solubility of different chemical species depends on the temperature at which water and rocks react. Critically, silica solubility decreases with decreasing temperature, and as hydrothermal waters cool, amorphous (noncrystalline) silica precipitates in subsurface flow paths [Fournier, 1985].

Past analyses of water chemistry at Black Diamond Pool have indicated that water and rocks there react at lower temperatures compared with systems farther south in Upper Geyser Basin, including at Old Faithful [Price et al., 2024]. These lower temperatures are more favorable for silica precipitation and may contribute to sealing flow paths and building pressure for hydrothermal explosions in Biscuit Basin.

Early Insights into the 2024 Explosion

The data collected following the explosion of Black Diamond Pool on 23 July 2024 are still being analyzed to provide a detailed account of the conditions preceding and following the event. However, some preliminary insights are available from the initial observations.

Many indicators point to the explosion being caused by self-sealing in the hydrothermal system, with the result that increases in subsurface pressure eventually overcame the strength of the sealing rocks—a common mechanism for hydrothermal explosions globally [Morgan et al., 2009; Montanaro et al., 2022]. The lack of a strong earthquake nearby, either before or during the explosion, indicates it was not seismically triggered.

Furthermore, some of the ejected debris—namely, minimally altered, high-porosity, and high-permeability conglomerates and sandstones—likely contained much of the liquid water that flashed to steam and powered the explosion (Figure 2). On the other hand, completely silicified and intensely altered low-permeability rocks also found in the debris field likely constituted the seal that contained the pent-up pressure before the explosion.

The initial analyses of the seismic and infrasound data, as well as observations from scientists and passing visitors, indicate that small explosions at Black Diamond Pool have continued since 23 July 2024 through to the present, posing an ongoing hazard. Some of these explosions have been accompanied by water surges flowing east into the nearby Firehole River and have been large enough to carry seismic instruments several meters downhill and partially bury others in fine sediment. Two witnessed events were observed to throw water, mud, and small rocks 20–30 feet (6–9 meters) into the air. A webcam installed in mid-May 2025 to better document activity at Black Diamond Pool captured a similar small eruption on 31 May 2025.

Better Science for Better Response

The scientific response to the 23 July 2024 hydrothermal explosion has focused on improving understanding of the event to inform strategies that can be used to detect, and potentially forecast, similar future explosions. New hazard maps and recent geophysical investigations will guide NPS’s response to ensure public safety within Biscuit Basin, helping to address specific questions such as when the basin can be reopened, whether walkways must be relocated, and what the short-term probability of another large explosive event at Black Diamond Pool is. Scientific investigation will also guide YVO’s efforts to deploy targeted monitoring to other hydrothermal areas in Yellowstone National Park.

Hydrothermal explosions in Yellowstone National Park are an underappreciated hazard, and a pressing need exists to better understand where, why, and how often they happen. Filling these knowledge gaps requires multidisciplinary studies that consortia like YVO and its collaborators are well suited to undertake. Ultimately, improved monitoring of hydrothermal hazards will aid risk assessment and mitigation and help park officials and visitors avoid dangerous situations in Biscuit Basin, elsewhere in Yellowstone National Park, and at hydrothermal systems worldwide.

Acknowledgments

We especially thank Jamie Farrell, who assisted with preparation of this article and led the deployment of temporary seismometers and infrasound arrays in Biscuit Basin after the July 2024 explosion. We also acknowledge the many people involved in event response, scientific investigation, and management and policy decisions associated with the 23 July 2024 explosion of Black Diamond Pool. Scientists and personnel from USGS, NPS, Colorado State University, the University of Utah, the University of Wyoming, and Montana Technological University who have contributed include Phillip Kondracki, Alex Hammerstrom, Kiernan Folz-Donahue, Elle Blom, Blaine McCleskey, Sara Peek, Shaul Hurwitz, Steven Rice, Carrie Guiles, Jaclyn Mcllwain, Hillary Robinson, Andy Parkinson, Lexi Peterson, Lisa Morgan, Pat Shanks, Greg Vaughan, Jen Lewicki, Alycia Cox, Michael Loya, Andrew Miller, Katie Copeland, Kallen Snow, and Adaeze Ugwu. We thank Shaul Hurwitz and Patrick Muffler for constructive reviews. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. government.

References

Breard, E. C. P., et al. (2014), Using the spatial distribution and lithology of ballistic blocks to interpret eruption sequence and dynamics: August 6 2012 Upper Te Maari eruption, New Zealand, J. Volcanol. Geotherm. Res., 286, 373–386, https://doi.org/10.1016/j.jvolgeores.2014.03.006.

Browne, P. R. L., and J. V. Lawless (2001), Characteristics of hydrothermal eruptions, with examples from New Zealand and elsewhere, Earth Sci. Rev., 52(4), 299–331, https://doi.org/10.1016/S0012-8252(00)00030-1.

Christiansen, R. L., et al. (2007), Preliminary assessment of volcanic and hydrothermal hazards in Yellowstone National Park and vicinity, U.S. Geol. Surv. Open File Rep., 2007-1071, 94 pp., https://pubs.usgs.gov/of/2007/1071/.

Fournier, R. O. (1985), The behavior of silica in hydrothermal solutions, in Geology and Geochemistry of Epithermal Systems, Rev. Econ. Geol., vol. 2, edited by B. R. Berger, P. M. Bethke, and J. M. Robertson, pp. 45–61, Soc. of Econ. Geol., Littleton, Colo., https://doi.org/10.5382/Rev.02.03.

Fournier, R. O., et al. (1991), Conditions leading to a recent small hydrothermal explosion at Yellowstone National Park, Geol. Soc. Am. Bull., 103(8), 1,114–1,120, https://doi.org/10.1130/0016-7606(1991)103%3C1114:CLTARS%3E2.3.CO;2.

Montanaro, C., et al. (2022), Phreatic and hydrothermal eruptions: From overlooked to looking over, Bull. Volcanol., 84(6), 64, https://doi.org/10.1007/s00445-022-01571-7.

Morgan, L. A., W. C. P. Shanks III, and K. L. Pierce (2009), Hydrothermal processes above the Yellowstone magma chamber: Large hydrothermal systems and large hydrothermal explosions, Spec. Pap. Geol. Soc. Am., 459, https://doi.org/10.1130/2009.2459(01).

Muffler, L. J. P., D. E. White, and A. H. Truesdell (1971), Hydrothermal explosion craters in Yellowstone National Park, Geol. Soc. Am. Bull., 82(3), 723–740, https://doi.org/10.1130/0016-7606(1971)82[723:heciyn]2.0.co;2.

Poland, M. P., et al. (2025), The first instrumentally detected hydrothermal explosion in Yellowstone National Park, Geophys. Res. Lett., 52(11), e2025GL115850, https://doi.org/10.1029/2025GL115850.

Price, M. B., et al. (2024), Historic water chemistry data for thermal features, streams, and rivers in the Yellowstone National Park area, 1883–2021, data release, U.S. Geol. Surv., Reston, Va., https://doi.org/10.5066/P9KSEVI1.

Thiéry, R., and L. Mercury (2009), Explosive properties of water in volcanic and hydrothermal systems, J. Geophys. Res. Solid Earth, 114(B5), B05205, https://doi.org/10.1029/2008JB005742.

Yellowstone Volcano Observatory (2022), Volcano and earthquake monitoring plan for the Yellowstone Caldera system, 2022–2032, U.S. Geol. Surv. Sci. Invest. Rep., 2022-5032, 23 pp., https://doi.org/10.3133/sir20225032.

Author Information

Lauren Harrison (lauren.n.harrison@colostate.edu), Colorado State University, Fort Collins; Michael Poland, Yellowstone Volcano Observatory, U.S. Geological Survey, Vancouver, Wash.; Mara Reed, University of California, Berkeley; Ken Sims, University of Wyoming, Laramie; and Jefferson D. G. Hungerford, National Park Service, Mammoth, Wyo.

Citation: Harrison, L., M. Poland, M. Reed, K. Sims, and J. D. G. Hungerford (2025), Hydrothermal hazards on display in Yellowstone National Park, Eos, 106, https://doi.org/10.1029/2025EO250233. Published on 27 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.

Research & Developments is a blog for brief updates that provide context for the flurry of news that impacts science and scientists today.

It’s a bird! It’s a plane! It’s… a bolide!

People in Georgia, Tennessee, and the Carolinas reported sightings of a fireball overhead on Thursday afternoon, 26 June. It is unclear whether it was a meteor or space junk entering Earth’s atmosphere. Meteors can exceed one meter in size and are referred to as bolides when they explode in the atmosphere.

Sometimes, meteorite pieces can be recovered on the ground after such an event. In this case, they may need to be fished out of the foundation of a home. One fragment was reported to have struck a roof in Henry County, Georgia, according to Atlanta news station 11 Alive.

Mike Hankey, operations manager of the American Meteor Society, told 11 Alive that the organization received more than 100 reports of fireball sightings within 2 hours. Most reported said the sighting occurred between 12:25 and 12:40 p.m. EDT.

He explained that bolides can enter the atmosphere at speeds of up to 50,000 miles (80,000 kilometers) per hour, but slow to hundreds of miles per hour as they near Earth’s surface.

“You don’t want to get hit by one,” he clarified. (We at Eos tend to agree.) “It can cause a lot of harm, damages. They’ll go through multiple floors of a home, oftentimes.”

The bolide was bright enough that it was captured briefly by NOAA’s GOES-19 satellite, around the border of Virginia and North Carolina.

NASA Jet Propulsion Laboratory’s Center for Near Earth Object Studies (CNEOS) fireballs database reports that this marks the 20th fireball detected by U.S. government sensors this year. However, the Geostationary Lightning Mapper aboard the NOAA-operated GOES East and GOES West satellites detected nearly 700 this year. In April, another bolide made headlines when it flew over Mexico City.

According to the Swinburne University of Technology, about 5,000 bolides fall to Earth each year, but very few are observed, in large part because so many of them enter the atmosphere over the ocean.

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

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

Source: AGU Advances

Deep earthquakes are still a mystery that has been debated for a long time, but no consensus has been made so far. They originate at depths of 500 to 700 kilometers where there are extreme pressure and temperature conditions that should prevent the failure mechanisms that generate shallow earthquakes. Despite decades of observations and various proposed theories, a coherent mechanism that accounts for deep earthquake magnitudes has yet to be identified.

Jia et al. [2025] present an unprecedented analysis of 40 deep earthquakes worldwide with large magnitudes. They find that most of them are governed by a common mechanism facilitated by shear thermal runaway, ultimately allowing earthquakes to grow larger and release more energy. This explanation applies to deep earthquakes across diverse environments, from the coldest slabs such as Tonga, to the warmest, including those beneath South America.

Citation: Jia, Z., Fan, W., Mao, W., Shearer, P. M., & May, D. A. (2025). Dual mechanism transition controls rupture development of large deep earthquakes. AGU Advances, 6, e2025AV001701. https://doi.org/10.1029/2025AV001701

—Alberto Montanari, Editor-in-Chief, AGU Advances

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Lake Tahoe’s sparkling, clear water is a point of pride among locals and a draw for tourists. Although the water clarity—measured by how deep visible light can penetrate—has decreased since measurements began in 1968, conservation efforts over the past 2 decades have stabilized it.

However, a new study published last month in Limnology and Oceanography Letters shows that ultraviolet (UV) light tells a different story. The depths to which UV radiation reaches in Lake Tahoe vary dramatically between extreme wet and dry years. Because UV radiation can affect chemical and biological processes, shifting underwater light environments between years could have significant implications for Lake Tahoe’s ecosystem.

A Question of Clarity

To measure water clarity in Lake Tahoe, a 1,645-foot-deep (594-meter-deep) freshwater lake straddling the border of California and Nevada in the Sierra Nevada Mountains, scientists drop a white disk into the water and record how deep they can see it. They use a similar approach to measure UV light, but because it’s invisible to our eyes, they drop a sensor that measures different wavelengths of UV light as it sinks.

Eighteen years ago, scientists at the University of California, Davis Tahoe Environmental Research Center began collecting UV data from the lake every 2 to 3 weeks, creating a long-term record rare for lakes anywhere in the world.

“You can use satellites to look at long-term trends in water clarity, and people have done that all over the U.S. and around the world,” said Kevin Rose, a freshwater ecologist at Rensselaer Polytechnic Institute in New York, but “a multidecade record of UV radiation is a unique asset.” Rose was not involved in the study.

Several studies have used data from the record, but limnologist Shohei Watanabe at the Tahoe Environmental Research Center and his colleagues wanted to do a comprehensive analysis of whether Lake Tahoe was experiencing changes in the penetration of UV light between 2006 and 2023.

Watanabe initially expected to see a gradual decrease in UV penetration over the study period, mirroring the trend in visible light. “Instead, we found a huge fluctuation in UV transparency year to year,” he said.

In drought years, such as 2014–2015, UV radiation penetrated deeper than in exceptionally wet years such as 2017, when the Sierra Nevada received its second-highest amount of precipitation since 1910.

“It’s an amazing difference,” Watanabe said. The most dramatic differences occurred during the spring and early summer, when solar radiation is at its strongest. UV radiation was 100 times stronger 10 meters (32 feet) below the surface and reached up to nearly 4 times deeper in summers during drought years.

The phenomenon occurs because wet years wash more particulates and dissolved organic matter off the slopes of the surrounding mountains and into the lake, which blocks the UV radiation.

Visible light showed only a twofold difference in how deep it penetrated the lake between wet and dry years because the longer wavelengths of visible light are not as easily blocked by dissolved organic matter in the water. To the naked eye, visitors might notice some changes in the water clarity between years, “but it’s not like a 100-fold difference,” Watanabe said.

A Sunburn on the Ecosystem

The balance of UV light and visible light is crucial in freshwater ecosystems. UV radiation breaks down dissolved organic matter, releasing carbon dioxide into the atmosphere. Just like UV light can give us a sunburn, it can harm freshwater organisms by damaging DNA and inhibiting photosynthesis. It can also affect zooplankton behavior—these organisms actively avoid harmful UV light by migrating deeper during the day.

For the most biologically damaging UV wavelengths, including 305 and 320 nanometers, the differences from year to year in Lake Tahoe were most pronounced.

UV radiation isn’t always harmful to the ecosystem, however. Rose noted previous research showing that it prevents invasive fish, such as bluegill, from successfully reproducing in Lake Tahoe’s clear waters because larvae don’t survive high UV exposure. The fish become restricted to murky nearshore areas such as marinas.

Drastic shifts in UV penetration between wet and dry years therefore imply big changes in the ecosystems in the lake—and those swings could get more intense with human-caused climate change. “When we think about Lake Tahoe, now, going through precipitation cycles, that also means potential biological damage,” Rose said. Fully understanding how these communities will react will require continued monitoring.

Similar UV cycles might also occur in other clear mountain lakes worldwide, but each lake system has unique characteristics that would influence light patterns. “I really want to stress the importance of long-term monitoring for this kind of environmental study,” Watanabe said.

Watanabe and his colleagues are now planning and performing studies to determine how these UV variations affect Lake Tahoe’s carbon cycle, primary productivity, and other biological processes. “That’s the next step,” he said.

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

Citation: Chapman, A. (2025), Precipitation extremes drive swings in Lake Tahoe’s UV exposure, Eos, 106, https://doi.org/10.1029/2025EO250234. Published on 26 June 2025.

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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-

This image shows the crown of the landslide:-

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:-

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:-

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

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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.

“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?

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.

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?

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).

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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.

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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, 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.

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. 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.

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

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.

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. 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
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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 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:-

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]:-

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.

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