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SummaryCharacterizing ore deposits or mining dumps in terms of mineral content and grain size remains a challenge. Since the 1950s the Induced Polarization (IP) method has been successfully applied in ore prospecting. However, reliably interpreting field survey data requires comprehensive laboratory studies to establish a link between the IP parameters from empirical or phenomenological models and the type and quantity of ore minerals. In this study, we use numerical electrical networks to replicate the complex electrical resistivity spectra observed in experiments on sand-pyrite-water mixtures. A network consists of a 3D assembly of resistors, representing the saturated pore space, and leaky capacitors simulating the electrical behaviour of ore minerals. A sophisticated fitting procedure enables the precise determination of resistor and capacitor parameters, ultimately leading to strong agreement between measured and synthetic IP spectra. The results obtained from the 3D network align well with the classical Pelton model, which is based on a simple equivalent circuit. Our findings indicate that the network's chargeability depends on the fraction of capacitors in the system (i.e. the number of capacitors divided by the number of capacitors and resistors), and that the Pelton time constant of the measured spectra is closely related to the resistor and capacitor parameters. We argue that a 3D approach offers a more realistic framework, paving the way for future studies on the effects of ore grain size distribution, and the spatial arrangement of ore grains.

SummaryThe most widely used method to derive global geomagnetic field models for historical and longer timescales has long been regularized non-linear least squares inversion. It is based on spherical harmonics for the spatial part and cubic B-splines for the temporal dynamics. Recently, different versions of Bayesian inversion have been applied for this purpose. Early literature on the traditionally used formalism states the inverse problem in a Bayesian setting and discusses uncertainty estimation via the posterior covariance, but this view was lost in subsequent studies in the geomagnetic community. Here we aim to provide both geomagnetic field modellers and users of such models with a comparative view of the methods to enable them to better evaluate strengths and weaknesses of different models. We first describe the connection between regularized least squares and Bayesian inversion in general form in a linear, one-dimensional setting. A fully Bayesian perspective allows interpreting the regularization term as a form of prior and offers new ways of comparing models from both approaches. We then discuss the particular case of geomagnetic field modelling. We find that in comparison to Bayesian modelling approaches the prior corresponding to the widely used regularization does not imply reasonable field properties and does not lead to meaningful uncertainty estimates.

AbstractThis study presents a refined interpretation of the Jeokjung-Chogye Basin (JCB), a confirmed meteorite impact structure in South Korea, by integrating high-resolution gravity data, microtremor measurements, and borehole information. A total of 1 700 gravity stations including 1 000 newly acquired in 2023, were used alongside horizontal-to-vertical spectral ratio (HVSR) analysis and well-log constraints to characterize subsurface structures. To isolate the impact-induced deformation from overlying sedimentary effects, gravity stripping was applied to remove the signal from post-impact ejecta deposits. The residual gravity field was analysed using dip-curvature mapping and Euler deconvolution, which revealed concentric ring structures with displaced centres. These asymmetries, corroborated by 3D forward gravity modelling using IGMAS+, suggest a northeast-to-southwest impact trajectory with an oblique incidence angle of approximately 45°, contrasting with earlier estimates of ~55° from east to west. The final 3D density model achieves a strong correlation with observed anomalies (R ≈ 0.95) and successfully resolves variations in the autochthonous and basement layers.

Despite a warming climate, bone-chilling winter cold can grip parts of the U.S. In a study appearing in Science Advances, researchers found that two specific patterns in the polar vortex, a swirling mass of cold air high in the stratosphere, steer extreme cold to different regions of the country. One pattern drives Arctic air into the Northwest U.S., the other into the Central and Eastern areas.

Tungsten (W), a hard, heat-resistant, and corrosion-resistant metal, is indispensable to modern high-tech industries—from aerospace and defense to computing. While its global distribution is uneven, most tungsten deposits share defining geological traits: close ties to highly evolved, volatile-rich granites; formation from melted sedimentary rocks (anatexis) in tungsten-rich granitoids; and occurrence in back-arc or intraplate zones rather than convergent tectonic margins. These features have long supported theories of a purely crustal origin for tungsten mineralization.

Source: Global Biogeochemical Cycles

Whether from a forest on fire or gasoline powering a car, organic matter rarely combusts completely: Remnants such as char and soot can persist in the environment for decades. Over time, as physical and biological processes break down the scorched leftovers, some of the carbon they contain leaches into groundwater, lakes, and rivers, eventually making its way to the ocean.

This carbon, known as dissolved black carbon (DBC), represents the ocean’s largest identified reservoir of stable dissolved organic carbon. Yet the isotopic signature of DBC in the ocean does not match what rivers alone supply. This discrepancy suggests there are one or more unknown sources of DBC entering the ocean that are not accounted for in the global carbon budget.

To address this knowledge gap, Zhao et al. conducted six field surveys along China’s eastern coast, in the Jiulong, Changjiang (Yangtze), and Pearl River estuaries. By gathering samples during all four seasons, the researchers aimed to quantify changes in DBC and shed light on how it moves through coastal ecosystems toward the sea. Prior research focused only on individual estuaries and didn’t always account for how processes may vary across seasons and tide cycles.

The findings from the new study reveal submarine groundwater discharge (SGD) as a likely missing source of DBC. The scientists observed that as seawater pushed into estuaries during flood tides, DBC levels rose. Conversely, when water flowed out of the estuaries during ebb tides, DBC concentrations fell. They suggest that this pattern occurs because the salty ocean water that mixes into the estuaries during flood tides promotes the release of DBC from groundwater into the water column.

The researchers estimate that globally, SGD contributes approximately 20% of the riverine discharge of DBC that enters the ocean each year. Given the role that DBC plays in carbon sequestration and biogeochemical cycling in the ocean, the findings underscore the importance of including estuarine processes in global carbon models. (Global Biogeochemical Cycles, https://doi.org/10.1029/2025GB008532, 2025)

—Aaron Sidder, Science Writer

Citation: Sidder, A. (2025), Tracing black carbon’s journey to the ocean, Eos, 106, https://doi.org/10.1029/2025EO250248. Published on 11 July 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.

Marine scientist Matthew Mulrennan was piggybacking on a tourist vessel around the Antarctic Peninsula’s coasts, surveying a seabed teeming with life, when his underwater cameras came across a gray seafloor scarred with ridges.

Anchoring had churned up the sediment, leaving lifeless patches strewn with crushed sponges. The damage had narrowly missed three giant volcano sponges, which can live for up to 15,000 years and grow larger than the divers who study them.

“We saw a lot of life on the seafloor and not a lot of regulation around its protection,” said Mulrennan, founder of KOLOSSAL, an ocean exploration and conservation nonprofit in California.

Anchoring churns up the seabed, destroying life and leaving regular furrows, akin to plow marks. Credit: Matt Mulrennan/KOLOSSAL

Mulrennan’s footage, which was released alongside a recent study in Frontiers in Conservation Science, provides evidence that the seafloor impacts of anchoring now extend to remote polar waters.

A Vulnerable Ecosystem

Retreating sea ice is opening Antarctica’s coast to increasing amounts of ship traffic, including tourist cruises. “Most visitors want to see the penguins, seals, and whales,” Mulrennan said, but the seafloor, which is home to 95% of the continent’s biodiversity, “is where the real action is.”

With large areas of the Southern Ocean unexplored, scientists estimate that as many as 17,000 species might live on the seabed.

Colorful life lies on the Antarctic seabed, including the 50-armed death star starfish and the giant volcano sponge, the oldest animal on the planet. Credit: Matt Mulrennan/KOLOSSAL

Many Antarctic species, such as the giant volcano sponge, are uniquely adapted to extreme cold and play an important ecological role, Mulrennan said. “They filter water, sequester carbon, provide food and habitat.”

“These are probably some of the most vulnerable ecosystems to anchor in in the world.”

“These are probably some of the most vulnerable ecosystems to anchor in in the world,” Mulrennan said. Although relatively fast-growing tropical reef communities may start to recover from anchoring in roughly a decade or so, “it could take hundreds or potentially thousands of years for Antarctic ecosystems to grow in the exact same way,” he said.

Mulrennan surveyed 36 sites around the Antarctic Peninsula between 2022 and 2023, finding anchor damage only at Yankee Harbour on Greenwich Island.

He showed the footage to Sally Watson, a geophysicist at Earth Sciences New Zealand and a study coauthor, who matched the characteristically uniform, curved gouges to anchor damage observed elsewhere.

Anchors can dig through 80 centimeters of sediment, but most damage is caused by the connected chain, which sweeps sideways because of winds and currents and can excavate 50 centimeters of sediment where it lies on the seafloor. From above, the scars resemble a broomstick, explained Watson, composed of one main scour stemming from the anchor connected to a series of branching gouges dug as the chain shifts in the sediment.

“Most of the really important life is within the uppermost 10 centimeters,” Watson said. “Anchoring blasts through that.”

In 2022, Watson and her colleagues published the first estimate of anchoring’s global footprint, putting its damage on par with bottom trawling.

Anchors and Icebergs

Anchoring isn’t the only thing churning up the Antarctic seafloor. Icebergs can drift into shallow water and drag along the seabed—causing well-documented impacts around the Antarctic Peninsula’s coastline, said Lloyd Peck, a marine biologist from the British Antarctic Survey who was not involved in the study.

Diver surveys show that iceberg scouring can destroy up to 99% of life on the shallow seabed. Regularly uprooted by icebergs, shallow-living species recover relatively quickly, in around a decade.

Waters deeper than 30 meters are struck less often, Peck said, allowing complex, slow-growing organisms to establish themselves. The slow growth also means these deeper areas take longer to recover.

At Yankee Harbour, Mulrennan observed the scours in waters 70 meters in depth, so he is confident they were caused by anchoring rather than by icebergs. Peck agreed, noting the large, slow-growing volcano sponges nearby. “That suggests the iceberg scouring is going to be very rare here,” he explained.

“Activities in Antarctica are bound by strict conservation rules, yet ship anchoring goes almost completely unregulated.”

Peck said that compared to iceberg scouring, anchoring will have a minor imprint across the Antarctic Peninsula. But the location of an anchoring impact is as important as its scope, he noted. “This is about disrupting sheltered areas that icebergs can’t reach.”

Species-rich areas in deeper waters, such as Yankee Harbour, could be acting as refugia, Peck explained, reseeding surrounding areas with life after they are scoured by icebergs. To avoid wider ecosystem impacts, he said, “we should be making every effort to avoid anchoring in areas of undisturbed biodiversity.”

In addition to tourist cruises, research vessels, shipping fleets, and private yachts operate in Antarctic waters. “Activities in Antarctica are bound by strict conservation rules” for all visitors, Mulrennan said, “yet ship anchoring goes almost completely unregulated.”

Watson and Mulrennan have several suggestions to mitigate anchoring impacts, including limiting time vessels spend on anchor and the use of designated anchorages, where ecological impact can be monitored and limited.

Above all, anchoring needs wider recognition as a conservation concern, not just in Antarctica but globally, Watson said. “I think we could do better, by changing the way we anchor, the gear we use, but at least understanding that this is not a no-consequences game.”

—Erin Martin-Jones, Science Writer

Citation: Martin-Jones, E. (2025), Anchoring is damaging the fragile Antarctic seabed, Eos, 106, https://doi.org/10.1029/2025EO250246. Published on 11 July 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.

As Great Salt Lake's levels continue to sag, yet another strange phenomenon has surfaced, offering Utah scientists more opportunities to plumb the vast saline lake's secrets.

Rivers are Earth's arteries. Water, sediment and nutrients self-organize into diverse, dynamic channels as they journey from the mountains to the sea. Some rivers carve out a single pathway, while others divide into multiple interwoven threads. These channel patterns shape flood risks, erosion hazards and ecosystem services for more than three billion people who live along river corridors worldwide.

The remains of landscapes thought to have formed when ancient rivers flowed across East Antarctica have been discovered—and could help predictions of future loss from the ice sheet.

A new study conducted by geologists from the University of Florida and the University of Maryland reveals that, as land is exposed by melting glaciers, chemical reactions in the newly uncovered glacial sediments initially suppress greenhouse gas emissions.

A new study published in Nature Communications has found that 17.31% of tropical tree cover—an area spanning 395.9 million hectares (Mha)—has been consistently overlooked by global forest monitoring systems, exposing significant gaps in efforts to track deforestation and ecological degradation.

Four years ago, summer floods in Limburg—in the south of the Netherlands—drastically altered the riverbed of the Meuse, making accurate high-water forecasts even more difficult than usual. "This shows just how vulnerable and unpredictable the Meuse really is," says researcher Hermjan Barneveld.

A new real-time monitoring system captures minute-by-minute changes in toxic metals resulting from traffic pollution. Research indicates that non-exhaust sources, including brake wear, significantly contribute to urban health risks.

A total collapse of the roughly 80-mile-wide Thwaites Glacier, the widest in the world, would trigger changes that could lead to 11 feet of sea-level rise, according to scientists who study Antarctica. To better predict fractures that could lead to such a collapse—and to better understand the processes driving changes in Antarctic ice shelves—a team led by researchers at Penn State developed a new method to evaluate cracks that destabilize ice shelves and accelerate those losses.

Colossal volcanic eruptions like the kind that may have obliterated the dinosaurs more than 65 million years ago are caused by mantle plumes that rise from shifting underground mountains deep within the Earth's mantle, new research led by University of Wollongong (UOW) geophysicists and statistical scientists has revealed.

Mud volcanoes may be less imposing and less familiar than their distant cousins, lava volcanoes, but they come with hazards of their own, and their presence can signal hidden geologic processes shaping a landscape.

A team of geologists has now made a global map of submarine mud volcanoes, which they hope will help further the understanding of these little-known landforms. The study, published earlier this year in Scientific Data, mapped more than a thousand mud volcanoes in shallow seas. A million more may sit undiscovered deep in the world’s oceans.

No one had put all the mapped mud volcanoes in a single dataset until now, said study author Daniele Spatola, a marine geologist at Sapienza Università di Roma. Patterns that Spatola and his colleagues spotted in the dataset were published in another study appearing in the Journal of Marine Science and Engineering.

Hazards and Emissions

Mud volcanoes erupt when the pressure of gas trapped in rock becomes so strong that the rock is not able to hold it anymore, Spatola explained. Instead of lava, mud volcanoes spew a mix of gas, sediment, dissolved minerals, organic matter, water, and other fluids.

Fields of mud volcanoes are found in different geologic settings around the world, including in oil and gas fields, above mantle hot spots, near active faults, and at the edge of tectonic plates. Their presence and activity can give scientists important clues about tectonic and volcanic activity, said Nils Asp, a marine geologist at the Universidade Federal do Pará in northern Brazil who was not involved in the research.

“Mud volcanoes can be really dangerous.”

The unstable ground mud volcanoes create can put oil rigs, telecom cables, and other subsurface infrastructure at risk. “Mud volcanoes can be really dangerous,” Spatola said, particularly those on land.

They are also a not-insignificant source of methane and can also spew oxide-rich material and gases like carbon dioxide. “Carbon balances and climate models don’t take these emissions into account, and locally, they can be a problem in terms of increasing water acidity,” Asp said.

Having a global inventory of what submarine mud volcanoes look like and where they occur could help scientists estimate how much methane is bubbling through these vents and reveal where hazards lie.

Digging Through Records

Spatola and his colleagues gathered data from earlier published studies for roughly 1,100 submarine mud volcanoes—the majority in water no deeper than about 200 meters (650 feet). For 700 of them, the researchers either had full size, shape, and location information or had location information and were able to estimate geometry.

From these data, Spatola’s team created a freely available and downloadable database.

Most of the mud volcanoes in the database (65%) are located in the Mediterranean Sea. This distribution may reflect sampling bias, according to the authors. Areas in the eastern Mediterranean are often prospected for oil and gas, for example, and had more data available for the researchers to mine.

Other regions are less well mapped. “Probably, the number of mud volcanoes in the Atlantic is higher than what [appears in] the database, for example,” Spatola said.

Roughly 60% of mud volcanoes in the database are medium sized, with an area of 0.5–9 square kilometers. Small (<0.5 square kilometer) and large (>9 square kilometers) volcanoes together make up less than a third of the mapped volcanoes.

Giant mud volcanoes (defined as those covering an area larger than 20 square kilometers) are the rarest features in the database, making up about 4.5% of the mapped and classified total. Most of the very large or giant mud volcanoes are found in an area southeast of Japan where the Pacific and Philippine tectonic plates meet.

An initial analysis of the database showed that the more small-sized volcanoes a region has, the fewer large or giant volcanoes there are. This kind of pattern, known as a power law, is recognizable in many geologic processes, including earthquake distribution. The researchers also found that the size of a mud volcano is not necessarily related to how deep it sits below the sea surface.

The database could help inform regional health and safety measures, the study suggests, as the morphology of a mud volcano influences its geohazard potential. Tall and narrow volcanoes, for instance, are the most hazardous because they are more prone to instability.

Deep Challenges

Asp said that the database is “a solid starting point to be extended upon in further studies.”

Researchers don’t know how many submarine mud volcanoes there are because only a small portion of the ocean floor has been mapped.

“We need the help of the scientific community to improve this dataset. The more information we put into it, the better it will be.”

“In many areas, there might be a dozen kilometers of distance between one mapped stretch and another,” Asp said. “So we have no information of what is in that [unmapped] part of the seafloor.”

Some satellite imagery can penetrate a few dozen meters below the surface but not the deep ocean floor. To look that deep, marine researchers need ships capable of bathymetric mapping, but such instrumentation, including sonar and lidar equipment, is often prohibitively expensive.

The new study is a first attempt to create a database of submarine mud volcanoes, one that can be refined as more data are contributed. “We need the help of the scientific community to improve this dataset,” said Spatola. “The more information we put into it, the better it will be.”

—Meghie Rodrigues (@meghier.bsky.social), Science Writer

Citation: Rodrigues, M. (2025), Mapping mud volcanoes in shallow seas, Eos, 106, https://doi.org/10.1029/2025EO250245. Published on 10 July 2025. Text © 2025. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

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

Our modern society is increasingly reliant on multiple technologies that are vulnerable to the adverse effects of space weather. This necessitates effective public communication and awareness of various space weather phenomena as well as increased public engagement and preparedness for risk mitigation.

Chabanski et al. [2025] advocate for the development and implementation of a standardized naming convention of geomagnetic storms, along the lines of existing naming conventions in meteorology, astronomy, and geography.

The authors surveyed the top 50 geomagnetic storms over the past 47 years (since 1978), of which only five had names assigned by the scientific community. Drawing on lessons learned in other scientific disciplines, they propose the possible formation of an international working team comprised of International Space Weather Coordination Forum participants. This international team would implement a theoretical framework and a unified international standard for defining the criteria, protocols, and procedures for naming and cataloguing geomagnetic storms based on their minimum Disturbance Storm Time (Dst) indices and their solar origins.

This proposed initiative is about not only assigning names to geomagnetic storms but also empowering the public with the knowledge necessary to navigate the challenges of the 21st-century space environment.

Citation: Chabanski, S., de Montety, F., Lilensten, J., Poedts, S., & Spogli, L. (2025). The power of a name: Toward a unified approach to naming space weather events. Perspectives of Earth and Space Scientists, 6, e2025CN000285. https://doi.org/10.1029/2025CN000285

—Andrew Yau, Editor, Perspectives of Earth and Space Scientists

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.

Author(s): Tie-Huai Zhang, Wei-Min Wang, Yu-Tong Li, and Jie Zhang

Seeking for a high-gain fusion scheme is a hot issue in inertial confinement fusion community, especially after the successful fusion ignition at National Ignition Facility. Fast ignition provides an alternative due to its potential to reduce the energy of driven lasers and achieve higher target gai…

[Phys. Rev. E 112, 015204] Published Thu Jul 10, 2025

Author(s): Martin Lemoine

Building on his previous work, the author develops an analytical theory for particle acceleration due to electric fields in magnetohydrodynamic turbulence. The theory, that is also valid in several nonturbulent cases – and captures nonresonant mechanisms such as Fermi and betatron acceleration, magnetic pumping, curvature drift, and transit-time damping – should be of high value in the area of astrophysics, in particular for the study of relativistic particle acceleration.

#ClearMotivation #TechnicalAdvancement

[Phys. Rev. E 112, 015205] Published Thu Jul 10, 2025