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Author(s): Magnus F. Ivarsen, Jean-Pierre St-Maurice, Glenn C. Hussey, Kathryn McWilliams, Yaqi Jin, Devin R. Huyghebaert, Yukinaga Miyashita, and David Sibeck

During the 23 April 2023 geospace storm, we observed chorus-wave-driven, energetic particle precipitation on closed magnetic field lines in the dayside magnetosphere. Simultaneously and in the ionosphere's bottom side, we observed signatures of impact ionization and strong enhancements in the ionosp…

[Phys. Rev. E 112, 045203] Published Wed Oct 08, 2025

Author(s): Magnus F. Ivarsen, Jean-Pierre St-Maurice, Glenn C. Hussey, Daniel Billet, Devin R. Huyghebaert, Yaqi Jin, Yukinaga Miyashita, Satoshi Kasahara, Kaili Song, P. T. Jayachandran, Shoichiro Yokota, Yoshizumi Miyoshi, Kazuhiro Yamamoto, Atsuki Shinbori, Yoshiya Kasahara, Iku Shinohara, and Ayako Matsuoka

At night in Earth's polar regions, energetic aurorae frequently penetrate into the atmosphere, with the peculiar effect of driving turbulent electrojet currents in the bottomside ionosphere. During the day, however, Earth's plasma environment becomes highly conductive, owing to the constant flux of …

[Phys. Rev. E 112, 045204] Published Wed Oct 08, 2025

Author(s): L. Verra, M. Galletti, M. P. Anania, A. Biagioni, M. Carillo, E. Chiadroni, A. Cianchi, G. Costa, L. Crincoli, A. Del Dotto, M. Del Giorno, R. Demitra, G. Di Pirro, A. Giribono, V. Lollo, M. Opromolla, G. Parise, D. Pellegrini, R. Pompili, S. Romeo, G. Silvi, F. Stocchi, F. Villa, and M. Ferrario

Resonances play a crucial role in media sustaining oscillatory phenomena, such as plasmas. We show with experimental results and numerical simulations that the wakefields driven by individual successive bunches in overdense plasma superpose linearly, and that their amplitude increases along the trai…

[Phys. Rev. E 112, 045205] Published Wed Oct 08, 2025

A major slope collapse in frozen sediments in Canada highlights the role of progressive failure.

Back in January of this year, I posted fascinating a piece by Derek Cronmiller of the Yukon Geological Survey about the 17 December 2024 Takhini River landslide and river-ice tsunami, which occurred in Whitehorse, Yukon, Canada. The location of this landslide is at [60.8611, -135.4180]. As a reminder, this is a figure from his post showing the landslide:-

Surface elevation change detection comparing 2013 lidar DTM to a 2025 DSM created from UAV photos for the Takhini River landslide.

Derek has now published a more detailed article in the journal Landslides (Cronmiller 2025) that provides the definitive description of this event. One element of the article caught my attention. The piece examines in some detail the initiation of the landslide. Cronmiller (2025) observes that:-

“In the case of the 17 December 2024 Takhini landslide, all common triggers are conspicuously absent, and the timing appears to be random.”

The article concludes (rightly in all probability) that the initiating mechanism was progressive failure – i.e. that the slope underwent brittle failure through a tertiary creep mechanism. Under these circumstances no external trigger is needed.

As such, Cronmiller (2025) is much more than a simple (although fascinating) case study. As Derek writes:

“While progressive failure mechanisms are commonly discussed in rockslide and gravitational slope deformation literature, their role in producing landslides in surficial sediments is discussed relatively infrequently as acute triggers commonly mask the effect of this phenomenon’s contribution to slope failure. This case study provides an important example to show that acute triggers are unnecessary to produce landslides in dry brittle surficial sediments.”

I wholeheartedly agree.

Reference

Cronmiller, D. 2025 The 17 December 2024 Takhini River landslide and river-ice tsunami, Whitehorse, Yukon, Canada. Landslides. https://doi.org/10.1007/s10346-025-02622-8

Return to The Landslide Blog homepage 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.

A new study by researchers at the European Commission's Joint Research Center reveals that the Amazon rainforest has just undergone its most devastating forest fire season in over two decades, which triggered record-breaking carbon emissions and exposed the region's growing ecological fragility despite a slowing trend in deforestation.

П.И. Арсеев, М.Ю. Каган, В.В. Кведер, Н.Н. Колачевский, М.М. Коршунов, И.А. Некрасов, С.Г. Овчинников, О.В. Руденко, М.В. Садовский, А.И. Смирнов

The Antarctic Circumpolar Current (ACC) is Earth's largest oceanic current, circling around Antarctica from west to east in alignment with Earth's rotation. This cold ocean current is driven primarily by the westerly wind drift. Connecting the Atlantic, Pacific and Indian Oceans, the ACC is critical for global heat transport, the carbon cycle and the interoceanic exchanging of nutrients. The ACC thus influences the regional and the global climate, and impacts biodiversity.

On a scorching Texas afternoon, some Houston neighborhoods heat up far faster than others. New research from Texas A&M University shows vacant and abandoned land is a big reason why.

A University of Sydney student has developed a completely new way to peer inside coral fossils to recover lost records of past climate change.

A new study from the University of British Columbia shows that even modest increases in river flows can dramatically raise flood frequency, with major implications for infrastructure and community safety. The researchers call for a shift in flood management—from focusing solely on rare, large floods to tracking how often floods occur.

A helicopter flies low over the Appalachian Mountains, moving slowly above mostly forested lands of Maryland, Pennsylvania, and West Virginia. The aircraft carries a blue-and-white box holding instrumentation to detect unseen photon gamma rays created by radioactive decay within the rocks below. When a gamma ray reaches a specially designed crystal inside the box, it produces a flash of light—a reaction called scintillation—that provides information about the gamma ray’s properties and origins.

Measurements of natural, low-level radioactivity have been used in geologic applications for nearly a century.

Scintillation is the foundation of radiometric methods that provide passive and rapid assessments of the geochemical compositions of rock samples, cores, and outcrops, as well as of swaths of Earth’s surface. These methods measure ambient gamma ray energy signatures to determine which isotopes most likely produced them. Such data are then used to create maps of Earth’s surface and near subsurface where radioactive elements are present, even in low amounts.

Measurements of natural, low-level radioactivity have been used in geologic applications for nearly a century. But a new phase of open-access, high-resolution, airborne data collection funded and executed through the U.S. Geological Survey’s (USGS) Earth Mapping Resources Initiative (MRI) is providing novel insights for geologic mapping, critical minerals research, mine waste studies, and other applications.

From Geiger Tubes to Spectrometry

Radiometric methods developed rapidly following the discovery of radioactivity in 1896. Only a few decades later, petroleum explorations in the 1930s made use of Geiger tubes and ionization chambers to measure gamma rays emitted from boreholes. These early methods, which counted the total number of gamma rays detected, couldn’t discern individual radioelements, but they could reveal different sedimentary layers.

By the 1940s, scintillation crystals were light enough that instruments could be carried aboard airplanes for use in total-count radiometric surveys. And by the late 1960s, gamma ray sensors were accurate enough to distinguish specific source isotopes, providing capabilities for full gamma ray spectrometry [Duval, 1980; International Atomic Energy Agency, 2003].

Airborne gamma ray spectrometry provides rapidly and continuously collected geochemical information over large areas that is impossible to obtain from the ground.

During an airborne radiometric survey, an airplane, helicopter, or drone flies back and forth in a “mow-the-lawn” pattern to produce map view estimates of radioelement concentrations. The spatial resolution of the data depends on how closely the survey flight lines are spaced and on flying height: The farther the sensor is from the ground, the wider the area that is imaged—and the lower the resolution—at each point in time.

The results represent gamma rays emitted from roughly the upper 50 centimeters of the ground surface, whether bedrock or soil; shielding of these rays by vegetation is typically limited. Although many radioelements produce gamma rays, potassium, uranium, and thorium are the primary elements evaluated because they are relatively abundant on Earth and their decay sequences generate gamma ray signatures strong enough to be measured by airborne sensors [Minty, 1997; International Atomic Energy Agency, 2003].

Airborne gamma ray spectrometry provides rapidly and continuously collected geochemical information over large areas that is impossible to obtain from the ground. These surveys are often paired with simultaneous collection of magnetic data because the optimal flying speeds and heights are similar for both. These methods, when combined with ground truth geologic observations and sample analyses, offer a powerful tool for geologic mapping.

Resource Exploration Drives Data Collection

The earliest airborne radiometric datasets were total-count surveys collected primarily for uranium exploration by Australia, Canada, the Soviet Union, and the United States immediately after World War II. In the 1970s, continued interest in uranium led to initiation of the National Uranium Resource Evaluation (NURE), which supported airborne gamma ray spectrometry surveys measuring potassium, thorium, and uranium over the conterminous United States and parts of Alaska. These data, along with concurrent magnetic data, were released publicly. Around the same time, similar interest in Australia and Canada motivated regional-scale coverage in those countries.

To achieve national coverage, the NURE surveys were designed with very widely spaced flight lines 5–10 kilometers apart, and only a few areas were chosen for higher-resolution data collection. The data were useful primarily for reconnaissance rather than detailed exploration.

In the decades following the NURE surveys, sensor and processing technology improved remarkably, but only a limited number of public high-resolution radiometric surveys—covering about 1% of the country’s area—were flown in the United States (Figure 1). The lack of radiometric data was even more severe than that of magnetic data, which by 2018 covered almost 5% of the country [Drenth and Grauch, 2019]. Magnetic surveys were more common, perhaps because of their use for mapping buried faults, folds, and other geologic features in studies of mineral resources, natural hazards, and water resources (Figure 1).

Fig. 1. This map shows the areas covered by high-resolution airborne surveys across the conterminous United States before and since the launch of the Earth Mapping Resources Initiative (MRI). Radiometric surveys typically also include magnetic data collection, but the converse is not always the case. (“high resolution” is defined here as “Rank 1” or “Rank 2” using the nomenclature of Johnson et al. [2019] and Drenth and Grauch [2019] for radiometric and magnetic surveys, respectively. These rankings consider a variety of survey conditions, including the flight line spacing, flying height, whether GPS navigation was used, and whether data were recorded digitally.)

Since 2019, Earth MRI has been addressing this data scarcity, with the goal of improving knowledge of domestic critical mineral resources and the geologic regimes, or frameworks, within which they form and concentrate. Critical mineral resources such as lithium, graphite, rare earth elements (REEs), and many others are commodities that are essential for the U.S. economy and security but are at risk from supply chain disruptions. They are key components in numerous technologies, from cell phones and medical devices to advanced defense systems and renewable energy technologies.

These datasets and interpretations can also inform studies in other disciplines, such as of earthquake hazards.

Earth MRI takes a multidisciplinary approach that includes geologic mapping and collection of new data using lidar, airborne geophysical methods, and analyses of sample geochemistry, mineralogy, and geochronology. These datasets and interpretations, all freely and publicly available, provide broad information about critical minerals, their mineralizing systems, and their geologic frameworks. Such information can also inform studies in other disciplines, such as of earthquake hazards, and is especially useful for advising land use planners (e.g., in making decisions about setting areas for natural preservation, grazing, and recreation) and for informing and reducing the economic risk of costly mineral resource exploration.

Magnetic and radiometric data are the foundation of Earth MRI’s airborne geophysical coverage because they provide valuable information about geology, including areas under cover and vegetation, and their relatively low cost enables surveying of large areas. Additional funding from the 2021 Infrastructure Investment and Jobs Act has facilitated targeted studies using both hyperspectral and electromagnetic methods, which provide complementary imaging.

Bird’s-Eye Views of Geology Fig. 2. Airborne radiometric data collected over the Appalachian Valley and Ridge Province in Maryland, Pennsylvania, and West Virginia are shown here using a ternary color scale (magenta = potassium (K), cyan = thorium (Th), yellow = uranium (U)). These data, which are available from the USGS, highlight different lithologies of shallow and outcropping sedimentary layers. The image is draped over a shaded relief image of lidar-derived elevation for context. Click image for larger version.

Heavily folded and faulted sedimentary rocks of the Appalachian Valley and Ridge Province provide a dramatic example of the value of Earth MRI’s data collection for geologic applications. Earth MRI supported new airborne magnetic and radiometric data collection in 2022–2023 in this region to better understand the geologic framework of critical minerals in metal-bearing shales and manganese-iron sedimentary layers (Figure 2).

The data illustrate a diverse array of lithologies in close proximity (sometimes <1 kilometer apart), reflecting the structure and stratigraphy of layered sedimentary rocks. They reveal outcrops of shale formations containing varying amounts of potassium, thorium, or both, highlighting compositional information. Weathered carbonates and carbonate regolith show only elevated levels of potassium, whereas quartz sandstone is mostly devoid of radioelements except for sparse patches of uranium enrichment.

Accurate interpretation of airborne radiometric datasets requires complementary geologic knowledge from other sources because the presence of potassium, thorium, and uranium can be linked to several different minerals. For example, in hard rock terranes, elevated potassium often indicates mica and potassium feldspar in granites, granodiorites, or felsic volcanic rocks. However, elevated potassium may also indicate a history of hydrothermal alteration that formed potassium-rich minerals associated with economically significant ores, such as gold-copper porphyry deposits [e.g., Shives et al., 2000].

Radiometric detections of potassium can illuminate broad transport pathways from sites of erosion to sites of deposition.

In sedimentary environments, elevated potassium measurements may represent minerals such as illite. Or they may indicate recently eroded sands (from which potassium has not been dissolved and mobilized), such as those found in river floodplains. In those scenarios, radiometric detections of potassium can therefore illuminate broad transport pathways from sites of erosion to sites of deposition [Shah et al., 2021].

Colocated magnetic field data can provide needed complementary constraints on geologic interpretations, especially within hard rock terranes. For example, both mafic rocks and quartz sandstone usually show similarly low potassium, thorium, and uranium signatures. However, mafic rocks often express prominent magnetic anomalies, unlike quartz sandstone, allowing scientists to easily distinguish the two.

Critical Mineral Frameworks

In addition to their use for fundamental geologic mapping, new Earth MRI datasets are providing key information on domestic critical minerals—and in some cases imaging them directly. This is especially the case for REEs because many minerals that host REEs also contain thorium. For example, at California’s Mountain Pass, presently the only site of active REE production in the United States, airborne radiometric data show elevated thorium, uranium, and potassium concentrations over mineralized areas [Ponce and Denton, 2019].

Airborne radiometric surveys have also led to discoveries of critical minerals. In one case, data from a remote part of northern Maine revealed a highly localized thorium and uranium anomaly. The finding motivated a subsequent effort in which a multidisciplinary and multi-institutional team quickly investigated the area on foot. By combining geophysical data, geologic mapping, and analyses of rock samples, they discovered an 800- × 400-meter area with high concentrations of REEs, niobium, and zirconium, all considered critical commodities [Wang et al., 2023]. The depth of the mineralization, and thus the potential economic value, is not yet known, but a deposit in Australia with similar rock type, composition, and areal extent has been valued in the billions of dollars.

In another study, researchers used Earth MRI radiometric data collected over Colorado’s Wet Mountains to map REE mineralization in carbonatite dikes, veins in alkaline intrusions, and syenite dikes [Magnin et al., 2023]. Additional analyses of thorium levels and magnetic anomalies provided insights into the geologic environment in which these REE-bearing features formed, namely, that the mineralization likely occurred as tectonic forces stretched and rifted the crust in the area.

And over South Carolina’s Coastal Plain sediments, Shah et al. [2021] imaged heavy mineral sands containing critical commodities: REEs, titanium, and zirconium (Figure 3). These researchers are developing new constraints on critical mineral resource potential within individual geologic formations by evaluating the statistical properties of thorium anomalies.

Fig. 3. Critical minerals in ancient shoreline sands near Charleston, S.C., are highlighted in this map of airborne radiometric thorium data draped over lidar-derived shaded relief topography. Thorium is present in the mineral monazite, which also contains rare earth elements. Detecting Impacts from—and on—Humans

A new frontier in critical mineral studies focuses on the potential to tap unconventional resources, especially those present in mining waste and tailings.

A new frontier in critical mineral studies focuses on the potential to tap unconventional resources, especially those present in mining waste and tailings. Mining and mine waste features are scattered across the United States, sometimes presenting environmental or public health hazards. If critical minerals could be reclaimed economically from waste, proceeds could help to fund cleanup actions.

Early work with airborne data on this frontier focused, for example, on examining anomalous thorium concentrations in tailing piles from abandoned iron mines in the eastern Adirondack Highlands of upstate New York. Researchers found that the piles that contained REEs in the mineral apatite expressed thorium anomalies, whereas other piles were devoid of these critical commodities.

More recently, scientists identified uranium anomalies in datasets collected over stacks of phosphate mining waste, known as phosphogypsum stacks or “gypstacks,” in Florida (Figure 4). And data collected over coal mining waste sites in the Appalachian Mountains show elevated potassium, thorium, and uranium. Mine waste in both these areas is now being studied more closely as possible REE resources.

Fig. 4. Uranium anomalies (yellow and red) highlight mining areas, waste stacks, and, in some areas, dirt roads in this image of airborne radiometric data collected over the phosphate mining district in central Florida. Click image for larger version. Credit: background imagery: Google, Airbus; data: USGS

Radiometric surveys can also shed light on natural geologic hazards that affect human health. Radon gas, a well-known risk factor for lung cancer, is produced from the breakdown of radioelements, especially uranium, in soil and rock. By imaging areas with elevated uranium, radiometric surveys can delineate areas with higher radon risk.

In the 1980s, the U.S. Department of Energy commissioned a total-count survey over a small section of the Reading Prong in Pennsylvania, a geologic unit with known instances of uranium that also extends into New Jersey and New York, to map radon hazards. New Earth MRI datasets collected west of that part of Pennsylvania and elsewhere cover much larger areas and distinguish uranium, thorium, and potassium, providing a means for extensive radon risk evaluation.

Much More to Explore

Earth MRI airborne magnetic and radiometric surveys funded as of September 2025 have provided a roughly 18-fold increase in publicly available high-resolution radiometric data compared with what was available in 2018, and additional surveys are planned for 2026. However, the new total still represents only about 19% of the area of the United States (including Alaska, Hawaii, and Puerto Rico), so there is still a long way to go to achieve full national coverage.

A drone collects radiometric data over mining waste piles in southwestern New Mexico. These and other mine waste piles are being studied to see whether they hold critical mineral resources. Credit: Anjana Shah/USGS, Public Domain

The new open-access data present a wide variety of opportunities for study, from qualitative revisions of geologic maps to quantitative analyses that address questions about critical mineral resources and other societally important topics. These data are also inspiring innovative approaches, such as drone-based surveys using new ultralightweight sensors that can provide unprecedented spatial resolution, with uses in detailed mine waste studies, radon evaluation, and other applications [e.g., Gustafson et al., 2024]. Another new approach combines airborne radiometric data with sample geochemical data to evaluate critical minerals in clays [Iza et al., 2018].

Other novel applications that encourage economic development, maintain national security, and enhance public safety are waiting to be developed and explored.

Acknowledgments

We thank Tom L. Pratt and Dylan C. Connell for helpful 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

Drenth, B. J., and V. J. S. Grauch (2019), Finding the gaps in America’s magnetic maps, Eos, 100, https://doi.org/10.1029/2019EO120449.

Duval, J. S. (1980), Radioactivity method, Geophysics, 45(11), 1,690–1,694, https://doi.org/10.1190/1.1441059.

Gustafson, C., et al. (2024), Mine waste identification and characterization using airborne and uncrewed aerial systems radiometric geophysical surveying, Geol. Soc. Am. Abstr. Programs, 56(5), 1-6, https://doi.org/10.1130/abs/2024AM-403640.

International Atomic Energy Agency (2003), Guidelines for Radioelement Mapping Using Gamma Ray Spectrometry Data, IAEA-TECDOC-1363, Vienna.

Iza, E. R. H. F., et al. (2018), Integration of geochemical and geophysical data to characterize and map lateritic regolith: An example in the Brazilian Amazon, Geochem. Geophys. Geosyst., 19(9), 3,254–3,271, https://doi.org/10.1029/2017GC007352.

Johnson, M. R., et al. (2019), Airborne geophysical survey inventory of the conterminous United States, Alaska, Hawaii, and Puerto Rico (ver. 4.0, April 2023), data release, U.S. Geol. Surv., Reston, Va., https://doi.org/10.5066/P9K8YTW1.

Magnin, B. P., Y. D. Kuiper, and E. D. Anderson (2023), Ediacaran-Ordovician magmatism and REE mineralization in the Wet Mountains, Colorado, USA: Implications for failed continental rifting, Tectonics, 42(4), e2022TC007674, https://doi.org/10.1029/2022TC007674.

Minty, B. (1997), Fundamentals of airborne gamma-ray spectrometry, AGSO J. Aust. Geol. Geophys., 17, 39–50.

Ponce, D. A., and K. M. Denton (2019), Airborne radiometric maps of Mountain Pass, California, U.S. Geol. Surv. Sci. Invest. Map, 3412-C, scale 1:62,500, https://doi.org/10.3133/sim3412C.

Shah, A. K., et al. (2021), Mapping critical minerals from the sky, GSA Today, 31(11), 4–10, https://doi.org/10.1130/GSATG512A.1.

Shives, R. B., B. W. Charbonneau, and K. L. Ford (2000), The detection of potassic alteration by gamma-ray spectrometry—Recognition of alteration related to mineralization, Geophysics, 65, 2,001–2,011, https://doi.org/10.1190/1.1444884.

Wang, C., et al. (2023), A recently discovered trachyte-hosted rare earth element-niobium-zirconium occurrence in northern Maine, USA, Econ. Geol., 118(1), 1–13, https://doi.org/10.5382/econgeo.4993.

Author Information

Anjana K. Shah (ashah@usgs.gov), U.S. Geological Survey, Lakewood, Colo.; Daniel H. Doctor, U.S. Geological Survey, Reston, Va.; Chloe Gustafson, U.S. Geological Survey, Lakewood, Colo.; and Alan D. Pitts, U.S. Geological Survey, Reston, Va.

Citation: Shah, A. K., D. H. Doctor, C. Gustafson, and A. D. Pitts (2025), New maps of natural radioactivity reveal critical minerals and more, Eos, 106, https://doi.org/10.1029/2025EO250370. Published on 7 October 2025. Text not subject to copyright in the United States.
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

Hidden in Arctic sea ice are microscopic organisms that do more than eke out a meager existence on scraps of light filtered through their frozen habitat. New research has shown that ice diatoms have adapted to move efficiently through the ice, allowing them to navigate to better sources of light and nutrients. During in situ and laboratory experiments, ice diatoms glided through the ice roughly 10 times faster than diatoms from temperate climates and kept gliding even at −15°C, the lowest temperature recorded for single-celled organisms.

“People often think that diatoms are at the mercy of their environment,” said Manu Prakash, a bioengineering researcher at Stanford University in California and lead researcher on this discovery. “What we show in these ice structures is that these organisms can actually move rapidly at these very cold temperatures to find just the right home. It just so happens that home is very cold.”

These findings, published in the Proceedings of the National Academy of Sciences of the United States of America, may help scientists understand how microorganisms and polar ecosystems respond to climate change.

Gliding Through Life Researchers drilled several cores from sea ice in the Chukchi Sea to understand the movement patterns of diatoms. Credit: Natalie Cross

Diatoms are microscopic, single-celled algae that photosynthesize. Up to 2 million species of diatoms produce at least 20% of the oxygen we breathe and form the backbone of ecosystems throughout the world, from the humid tropics to the frigid poles. Scientists have known since the 1960s that diatoms live within and move through the ice matrix but have been unable to decipher how they do it.

“Ice is an incredible porous architecture of highways,” Prakash explained. “Light comes from the top in the ice column, and nutrients come from the bottom. There is an optimal location that [a diatom] might want to be, and that can only be possible with motility.” (Motility is the ability of an organism to expend energy to move independently.)

Prakash and a team of researchers sought to observe ice diatoms’ movements in situ and so set off for the Chukchi Sea aboard the R/V Sikuliaq. On a 45-day expedition in 2023, they collected several cores from young sea ice, extracted diatoms from the cores, and studied the diatoms’ movements on and within icy surfaces under a temperature-controlled microscope customized for subzero temperatures.

At temperatures down to −15°C, Arctic ice diatoms actively glided on ice surfaces and within ice channels. The researchers said that this is the lowest temperature at which gliding motility has been observed for a eukaryotic cell.

“Life is not under suspension in these ultracold temperatures. Life is going about its business.”

“Life is not under suspension in these ultracold temperatures,” Prakash said. “Life is going about its business.”

“This is a notable discovery,” said Julia Diaz, a marine biogeochemist at Scripps Institution of Oceanography in San Diego. “These diatoms push the lowest known temperature limit of motility to a new extreme, not just compared to temperate diatoms, but also compared to more distantly related organisms.” Diaz was not involved with this research.

“Since the 1960s, when J. S. Bunt first described sea ice communities and observed that microbes were concentrated in specific layers of the ice, it has been obvious that they must have a means to navigate through ice matrices,” said Brent Christner, an environmental microbiologist at the University of Florida in Gainesville who also was not involved with this research. “This study makes it clear that some microbes traverse gradients in the ice by gaining traction on one of the most slippery surfaces known!”

“While these diatoms are clearly ice specialists, they nevertheless appear to be equipped with the equivalent of all-season tires!”

The team compared the movement of ice diatoms to those of diatoms from temperate climates. On both icy and glass surfaces under the same conditions, ice diatoms moved roughly 10 times faster than temperate diatoms. In cold conditions on icy surfaces, temperate diatoms lost their ability to move completely and just passively drifted along. These experiments show that ice diatoms adapted specifically to their extreme environments, evolving a way to actively seek out better sources of light to thrive.

“I was surprised the ice diatoms were happily as motile on ice as glass, and much faster on glass that the temperate species examined,” Christner said. “While these diatoms are clearly ice specialists, they nevertheless appear to be equipped with the equivalent of all-season tires!”

On ice (left) and on glass (right) surfaces, ice diatoms (top) move faster than temperate diatoms (bottom). All experiments here were conducted at 0°C and are sped up 50 times to highlight the diatoms’ different gliding speeds. Credit: Zhang et al., 2025, https://doi.org/10.1073/pnas.2423725122, CC BY-NC-ND 4.0 Can Diatoms Adapt to Climate Change?

The Arctic is currently experiencing rapid environmental changes, warming several times faster than the rest of the world. Arctic climate change harms not only charismatic megafauna like polar bears, Prakash said, but microscopic ones, too.

“These ecosystems operate in a manner that every one of these species is under threat.”

Diatoms are “the microbial backbone of the entire ecosystem,” Prakash said. “These ecosystems operate in a manner that every one of these species is under threat.”

Prakash added that he hopes future conservation efforts focus holistically on Arctic ecosystems from the micro- to macroscopic. Future work from his own group aims to understand how diatoms’ gliding ability changes under different chemical conditions like salinity, as well as how the diatoms shape their icy environment.

“Scientists used to think that sea ice was simply an inactive barrier on the ocean surface, but discoveries like these reveal that sea ice is a rich habitat full of biological diversity and innovation,” Diaz said. “Sea ice extent is expected to decline as climate changes, which would challenge these diatoms to change the way they move and navigate their polar environment. It is troubling to think of the biodiversity that would be lost with the disappearance of sea ice.”

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

Citation: Cartier, K. M. S. (2025), Ice diatoms glide at record-low temperatures, Eos, 106, https://doi.org/10.1029/2025EO250371. Published on 7 October 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.

Georgia Tech researchers have developed a mathematical formula to predict the size of lakes that form on melting ice sheets—discovering their depth and span are linked to the topography of the ice sheet itself.

An analysis of forest-based projects funded through the sale of carbon credits shows that 10% of them may have a net warming effect on the climate because of the way they alter Earth's albedo, or how much sunlight is reflected back into space.

Author(s): Lipan Qin, Ze Chen, Meiqi Sun, Jin Yan, Yan Tian, Zhongyi Chen, Yan Wang, Xunjie Ma, Xueqing Yan, and Yunliang Wang

A unique coherent bremsstrahlung (CB) regime is proposed for the generation of an isolated half-cycle attosecond pulse (AP), even for the case of a multicycle driving laser pulse, which is realized by the laser pulse interacting with the double-foil target. When the rising edge of the laser pulse in…

[Phys. Rev. E 112, 045202] Published Tue Oct 07, 2025

The June 2023 heat wave in northern European seas was "unprecedented but not unexpected," new research shows.

In July 2025, I recorded 71 fatal landslides worldwide, with the loss of 214 lives.

Each year, July is one of the key months for the occurrence of fatal landslides globally as the Asian monsoon season cranks up to full strength. Thus, it is time to provide an update on fatal landslides that occurred in July 2025. This is my dataset on landslides that cause loss of life, following the methodology of Froude and Petley (2018). At this point, the monthly data is provisional. I will, when I have time, write a follow up paper to the 2018 one that describes the situation since then.

In July 2025 I recorded 71 fatal landslides worldwide, with the loss of 214 lives. The average for the period from 2004 to 2016 was 58.1 fatal landslides, so this is considerably higher than the long term mean, although it is much lower than 2024, which saw 99 fatal landslides.

So, this is the monthly total graph for 2025 to the end of July:-

The number of fatal landslides to the end of July 2025 by month.

Plotting the data by pentad to the end of pentad 43 (29 July), the trend looks like this (with the exceptional year of 2024, plus the 2004-2016 mean, for comparison):-

The number of fatal landslides to 29 July 2025, displayed in pentads. For comparison, the long term mean (2004 to 2016) and the exceptional year of 2024 are also shown.

The data shows that the acceleration in the rate of fatal landslides occurred much later in the annual cycle than was the case in 2024. It was only late in the month that the rate started to approach that of 2024. Indeed for much of the month, the fatal landslide rate (the gradient of the line) is broadly similar to the long term mean, albeit with a much higher starting point.

But note also the distinct acceleration late in the month, which makes what then happened in August 2025 particularly interesting. Watch this space.

Notable events included the 8 July 2025 catastrophic debris flow at Rasuwagadhi in Nepal, but no single landslide killed more than 18 people in July 2025.

I often draw a link between the rate of fatal landslides and the surface air temperature. The Copernicus data shows that July 2025 was “0.45°C warmer than the 1991-2020 average for July with an absolute surface air temperature of 16.68°C“. It was the “third-warmest July on record, 0.27°C cooler than the warmest July in 2023, and 0.23°C cooler than 2024, the second warmest.”

Reference

Froude M.J. and Petley D.N. 2018. Global fatal landslide occurrence from 2004 to 2016. Natural Hazards and Earth System Science 18, 2161-2181. https://doi.org/10.5194/nhess-18-2161-2018

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SummaryA strong earthquake sequence in Storfjorden, south of Svalbard, was initiated by an Mw 6.1 event on 21 February 2008. Earthquake distribution and fault plane solutions indicate that seismic activity is controlled by unmapped NE-SW striking oblique-normal faults, contrasting with the major N-S oriented faults mapped onshore Svalbard. We present a geophysical model derived from an ocean bottom seismometer profile crossing the seismogenic zone to identify structures in the crust and uppermost mantle that potentially control the earthquake source mechanism. Travel-time forward modeling using raytracing, combined with travel-time tomography and gravity-magnetic modeling, reveal distinct crustal domains across the earthquake region. Crystalline crustal P-wave velocities range from 6.1 km/s to 6.7 km/s at the Moho depth in the eastern section. The western profile section exhibits a higher Vp velocity lower crust (6.6–7.0 km/s) with Vp/Vs ratios of 1.75–1.8 and high density (∼3100 kg/m³). Basement depth reaches 8 km in the west, forming a sedimentary basin, and shallows eastward. The Moho remains relatively flat at 29-32 km depth throughout the profile. The N-S oriented Caledonian suture, identified from deep seismic and potential field data, traverses the Storfjorden earthquake zone. The lithological contacts within the suture zone, inferred from the new OBS data, may facilitate seismic failure oblique to the N-S oriented structure, following the regional stress field.

SummaryWe developed a new amplitude correction method for receiver function imaging to analyze velocity contrasts along dipping interfaces. Because receiver function imaging typically assumes a horizontally layered structure, corrections are needed for amplitude and polarity variations of P-to-S converted phases when analyzing dipping interfaces. However, previous studies have not adequately addressed these effects, and improved receiver function analysis is required to better delineate dipping structures, such as subducting plate surfaces and the oceanic Moho. Therefore, we propose formulae that quantify converted S-wave amplitude variations between horizontal and dipping interfaces. This relationship is expressed as a function of the back azimuth, the ray parameter of an incident P wave, and the dip angle and dip direction of a dipping interface, and in this study, the geometry of the dipping interface (dip angle and dip direction) is assumed. We applied these formulae to receiver function imaging using synthetic and observed data and confirmed that the amplitude of seismic discontinuities was successfully reproduced. This method enables the use of numerous receiver functions regardless of the back azimuths of incident P waves, thereby providing more detailed amplitude estimations for dipping interfaces.

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