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Researchers have built on past studies and introduced new methods to explore the nature and role of subsurface fluids, including water, in the instances and behaviors of earthquakes and volcanoes. Their study suggests that water, even heavy rainfall, can play a role in or even trigger seismic events. This could potentially lead to better early warning systems.

Publication date: Available online 17 September 2025

Source: Advances in Space Research

Author(s): Xue Chen, Na Yang, Yifan Qi

Publication date: Available online 15 September 2025

Source: Advances in Space Research

Author(s): Rabia Rasheed, Biyan Chen, Wenfei Mao, Syed Amer Mahmood, Wu Lixin

Publication date: Available online 15 September 2025

Source: Advances in Space Research

Author(s): Meltem Koroglu, Ozan Koroglu, Feza Arikan, Orhan Arikan

Publication date: Available online 13 September 2025

Source: Advances in Space Research

Author(s): Oladayo O. Afolabi, Claudia M.N. Candido, F. Becker-Guedes, Christine Amory-Mazaudier, Rolland Fleury

Publication date: Available online 13 September 2025

Source: Advances in Space Research

Author(s): Emilia Correia, Eduardo P. Macho, Juliano Moro, Alessandro J. de Abreu, Christiano G.M. Brum, José H. Fernandez, Gareth Chisham, José V. Bageston

If you've ever held or beheld a diamond, there's a good chance it came from a kimberlite. Over 70% of the world's diamonds are mined from these unique volcanic structures. Yet despite decades of study, scientists are still working to understand how exactly kimberlites erupt from deep in Earth's mantle to the surface.

The largest salt flat in the world is Salar de Uyuni in Bolivia, a popular tourist attraction due to its stunning mirror-like surface when covered with a thin layer of water. While considered by many to be the "world's largest natural mirror," this claim had not been scientifically verified. Now, in a study published in the journal Communications Earth & Environment, scientists set out to confirm the effect and discovered that the surface is more complex than previously thought.

Ephemeral desert rivers known as wadis—lifelines for biodiversity and water in some of the world's driest landscapes—are being dangerously constricted by human activity, new research has found.

A new study published in the journal Nature Communications by researchers from the IBS Center for Climate Physics (ICCP) at Pusan National University in the Republic of Korea reveals that global warming is accelerating the risk of multi-year droughts that can lead to extreme water scarcity, threatening water demands in cities, agriculture, and livelihoods worldwide, already within the coming decades.

University of Nebraska–Lincoln's S. Kathleen Lyons is providing a new framework—Earth system engineering—for examining how organisms, including humans, have fundamentally altered ecosystems on a global scale across hundreds, thousands or millions of years.

Andean glaciers advanced during an acute period of climate change at the end of the last Ice Age, new research has found.

For decades, as Jill Kenny drove around her hometown of Tāmaki Makaurau Auckland, Aotearoa New Zealand, the now-retired geologist and geomorphologist wondered about the shape of the landscape. Auckland, the country’s largest urban area, is located on a volcano-studded isthmus on the North Island. Obvious volcanic mounds aside, why does the city have the shape it does?

Kenny noticed similar flat, eroded surfaces at different heights above sea level and one day in 2004 had an aha moment: Maybe these surfaces were at different elevations because they had been offset by faults. In other places, scientists can trace the echo of fault lines in the landscape or through seismic data, but Auckland has few earthquakes and is covered over by a patchwork of small lava flows and ash deposits, as well as by a modern concrete jungle.

Were there faults hidden beneath the city, and could any of them still be active?

A Passion Project

For years, Kenny trawled through paper and digital records detailing data culled from boreholes drilled through the lava and into Auckland’s underlying sedimentary rock. The boreholes were part of geotechnical investigations conducted for construction purposes and resulted in a total of 2,000 logs.

In those records was evidence of Miocene epoch layers of sandstone and mudstone called the Waitematā Group. The top of this layer, which eroded between 15 million and 5 million years ago, is the “only potential marker horizon that can be followed with any certainty across the Auckland region,” wrote Kenny and University of Auckland volcanologist Jan Lindsay in a 2012 paper describing the borehole research. That study identified a number of previously hidden faults under Auckland, as indicated by adjacent boreholes showing the surface suddenly raised or lowered along a consistent line.

In the years since Kenny and Lindsay’s 2012 paper, Auckland borehole data have proliferated. Logs that were once closely guarded by companies and organizations have been brought together in the New Zealand Geotechnical Database.

“Every little extra piece of information adds to the overall jigsaw puzzle,” said Lindsay.

Now, in a new study published in the New Zealand Journal of Geology and Geophysics, Kenny, Lindsay, and colleagues have used information from 8,200 boreholes in addition to new remote sensing and geophysical data to provide a revised model of post-Miocene faulting in the Auckland region. The model includes a new geospatial database, fault maps, and a suggested standard methodology for classifying obscured urban faults. The research identifies 10 likely and 25 possible faults in the region and erases some nonfaults that have been incorrectly propagated through the literature for decades.

Jill Kenny and colleagues trawled through data from 8,000 urban boreholes to identify 10 likely and 25 possible faults under Auckland. Credit: Kenny et al., 2025, https://doi.org/10.1080/00288306.2025.2519722, CC BY-NC-ND 4.0

“This paper is really a passion project,” said Lindsay. “It was a long, painstaking process, but we think we’ve ended up with a really robust catalog of buried faults in Auckland with a range of different confidences attached to them.”

Finding Urban Faults

While earthquakes are among the deadliest threats to urban areas, cities are tricky places to find faults, said Nicolas Harrichausen, who studies crustal deformation at the University of Alaska Anchorage but was not involved in the New Zealand research. Surface offsets can be just a few meters across, and when a shopping center, road, high-rise, or house is built, evidence of the fault is erased.

Another problem is access. “Say you do find something that is interesting—you can’t go dig a trench in somebody’s yard or dig up a street in the name of finding a potential fault,” said Harrichausen, who recently discovered an active fault in the city of Victoria on Vancouver Island, Canada.

Finally, seismic surveying is one of the most common fault-finding methods, and cities are just seismically noisy places. Vibrations from construction and highways consistently interfere with seismic signals. Some cities restrict or even ban seismic surveys for ecological reasons.

However, cities do have some advantages when compared to places like the extremely remote Alaskan fault he’s currently investigating, Harrichausen said: People are already digging lots of holes.

The new Auckland borehole database is a great starting point for research into the geomorphology of the region, Harrichausen said, but because of the ancient age of the marker horizon, “for earthquake hazard, it’s just kind of a baseline.” The United States considers a fault active if it’s ruptured in the past 12,000 years. In New Zealand, it’s 125,000 years. So far, the faults Kenny and Lindsay have identified can be constrained only to the past 5 million or so years.

“It may be that none of [the suggested Auckland faults] are active,” Lindsay acknowledged. “But we need to better understand our faults and how active they are in order to work out what our actual seismic risk is.”

The study has revealed several compelling candidates for further investigation, she said, including one fault near the peninsula suburb of Bucklands Beach, where offset evidence from the boreholes lines up with a visible scarp through a golf course. “If I were studying faults in Auckland, that’s where I would start,” said Harrichausen.

Where Magma Meets Fault

Even if none of the Auckland faults turn out to be active, for Lindsay, a volcanologist who leads the transdisciplinary Determining Volcanic Risk in Auckland project, the fault maps and database are also the starting point for another line of inquiry with significant implications for the people of the city.

“We need to know as much as we can about the rocks beneath our feet.”

The new maps show that the region’s volcanoes consistently erupted near the faults and associated structures, but not right along them. “Volcanologists are not in agreement as to whether magma prefers to move along faults or whether it prefers to move between faults,” said Lindsay. There seems to be some relationship between the structural fabric of the region and its volcanism, she and her coauthors wrote.

“In order to better understand the active volcanoes in Auckland, we need to know what the subsurface looks like,” Lindsay said. “We need to know the structure, we need to know where the faults are—we need to know as much as we can about the rocks beneath our feet.”

—Kate Evans (@kategevans.bsky.social), Science Writer

Citation: Evans, K. (2025), “Passion project” reveals Auckland’s hidden urban faults, Eos, 106, https://doi.org/10.1029/2025EO250354. Published on 23 September 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.

Kelp forests are underwater jungles and some of Earth’s most productive ecosystems, absorbing carbon, providing refuge for a myriad of marine life, and buffering vulnerable shoreline communities and infrastructure. But kelp ecosystems are under increasing climate stress and have been whittled down by overgrazing urchins as key food webs have collapsed.

“Our results suggest that kelp canopy can be a useful indicator of ecosystem resilience within MPAs under climate stress.”

New research led by a team from the University of California, Los Angeles (UCLA) and published in the Journal of Applied Ecology examines the effects of marine protected areas (MPAs) on giant and bull kelp forests off the coast of California. When comparing kelp in protected and unprotected waters, researchers found only modest differences in the surface layer of fronds. Following climate disturbances like marine heat waves, however, kelp within MPAs proved far more resilient, especially in Southern California.

“Our results suggest that kelp canopy can be a useful indicator of ecosystem resilience within MPAs under climate stress,” said Emelly Ortiz-Villa, a graduate student at UCLA and lead author of the study.

California as a Bellwether

California’s kelp forest ecosystems are threatened by factors such as marine heat waves and imbalanced food webs. As sea surface temperatures get hotter, researchers say, California’s experience may be a bellwether for temperate ecosystems globally.

During a catastrophic marine heat wave that struck the California coast between 2014 and 2016, Northern California lost more than 90% of its kelp canopy, which wreaked havoc on marine food webs as well as coastal economies that rely on tourism and fishing.

Compounding the threat posed by marine heat waves is the purple sea urchin, an animal that can devour kelp faster than the seaweed can reproduce. Predators of the sea urchin, including sea stars and sea otters, face pressures, including disease and habitat loss. When urchins outnumber their predators, once lush and verdant kelp forests can become spindly outcrops nicknamed “urchin barrens.”

In the future, said Ortiz-Villa, “research should examine how multiple stressors interact to influence kelp forest recovery, so we can better pinpoint where and when MPAs are most effective at enhancing resilience.”

“What We Mean by Protected”

Marine managers have long sought tools to buy time for kelp forests to recover.

MPAs are one such tool. Many MPAs limit or ban extractive activities, including fishing, but until now, their effectiveness for kelp conservation remained understudied. Using 4 decades of Landsat imagery of the California coast, researchers compared 54 kelp forests in MPAs to those with similar environmental features in unprotected waters.

Following climate disturbances like the 2014–2016 marine heat wave, researchers found an 8.5% increase in kelp coverage in fishing-restricted MPAs. In these protected areas, healthy populations of predator species like California sheepshead and spiny lobsters helped control sea urchin populations that might otherwise have overwhelmed compromised kelp forests.

There’s “a growing body of evidence that we need to be more targeted in terms of what we mean by protected.”

Previous research established the value of MPAs for preserving biodiversity, but this study is among the first to document their advantage to kelp forests. “It’s important to demonstrate that there is an additional benefit of MPAs, and they can be an extra part of the toolbox for protecting kelp forests,” said Aaron Eger, director of the Kelp Forest Alliance and a postdoctoral fellow at the University of New South Wales in Australia who was not involved in the study.

While MPAs tend to follow guidelines established by the International Union for Conservation of Nature, their levels of protection and management can differ greatly. Reserves range from strictly protected “no-take” areas, where all extractive activities are prohibited, to “multiple-use” zones that accommodate fishing and industrial operations. Some MPAs even allow controversial bottom-trawling practices.

The differing standards are “part of a growing body of evidence that we need to be more targeted in terms of what we mean by protected,” said Eger.

—Amelia Macapia (@ameliamacapia), Science Writer

Citation: Macapia, A. (2025), Marine protected areas show promise for kelp forest recovery, Eos, 106, https://doi.org/10.1029/2025EO250350. Published on 23 September 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.

Australia's worrying future under climate change was laid bare last week when the first National Climate Risk Assessment was released. It revealed extreme heat, fires, floods, droughts and coastal inundation already threatens lives and livelihoods—and will wreak further havoc in coming decades.

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

Ice sheets can have a large impact on the surrounding land and sea where they form, which can create many different landforms. One such landform is called a “glacial forebulge,” which is a long hill that forms in front of an ice sheet. These glacial forebulges are important to understand since they influence sea level and earthquake activity in North America and Europe.

A new article in Reviews of Geophysics digs deeper into the characterization of glacial forebulge dynamics. Here, we asked the authors to give an overview of glacial forebulges, how scientists study them, and what questions remain.

How would you define a glacial forebulge to a non-specialist?

Figure 1: Conceptual model of a glacial forebulge. The glacial forebulge is the upheaval of the lithosphere in front of the ice sheet. This model is based on Stewart et al. [2000], Grollimund and Zoback [2003], Keiding et al. [2015], and R. Steffen et al. [2021]. Lithostatic strength distribution based on Bürgmann and Dresen [2008]. Credit: Brandes et al. [2025], Figure 1

A glacial forebulge is an upheaval of the Earth’s surface that is formed in front of an ice sheet and runs parallel to the ice margin. These form because the ice mass bends the lithosphere and deforms the Earth’s surface. Below the ice load, a depression is formed, whereas outside the ice sheet, there is a gentle upward bending of the surface that forms the forebulge. This bending is supported by Earth’s lithosphere and mantle material that flows away from the area pushed down by the ice sheet.

For the large ice sheets that covered northern Europe and North America during the last glacial period, state-of-the-art numerical models show that the crest, or the highest point, of the forebulge has a maximum height of approximately 50 meters and 90 meters in these areas, respectively. Additionally, the crest can be one or two hundred kilometers away from the ice margin’s maximum extent around 20,000 years ago.

Why is it important to understand glacial forebulges?

The formation, geometry, and motion of the glacial forebulge affects sea level, river flow paths, and earthquake activity in North America and Europe. Though the large ice sheet of the last glaciation is already gone, remnants of the forebulge still exist. With the ice load gone, the area that was below the ice is uplifting and, consequently, the area of the forebulge now subsides. This process is slow and still ongoing, because the lithosphere cannot move independently from the underlying mantle. The mantle has a high viscosity and flows slowly. The subsidence in the forebulge area is on the order of a few millimeters per year. At coastlines, this subsidence can result in a rising sea level. The subsidence of the forebulge area also changes the stress state of the lithosphere, which could lead to a reactivation of pre-existing faults that can cause earthquakes.

Figure 2: Stresses in the lithosphere related to the glacial forebulge. The ice sheet loads the lithosphere and causes a depression below the ice sheet and an upheaval outside the ice sheet. The bending causes stresses in the lithosphere indicated by the arrows. Arrows that point towards each other indicate compressional stresses (material is pushed together), whereas arrows pointing in opposing directions indicate extensional stresses (material is pulled apart). These stresses change, when the ice melts. The figure is based on Stein et al. [1989], Stewart et al. [2000], Grollimund and Zoback [2003], and Keiding et al. [2015]. Credit: Brandes et al. [2025], Figure 14

How do scientists observe and measure glacial forebulges?

In the early years of forebulge research, the existence of a glacial forebulge was predicted by theoretical considerations and calculations assuming that the Earth’s surface before the onset of glaciation was “more-or-less flat,” and the deformation was due to the loading and unloading of a single ice sheet. These models were used to interpret the observed relative sea level data in the near field of the ice centers in Northern Europe and North America. In particular, these correspond to a transition zone between a zone showing pure land emergence and a zone showing pure land submergence in the pattern of global sea level change. These zones are carefully explained in our study.

Figure 3: Visualization of the different zones of relative sea level, predicted by state-of-the-art numerical models that simulate glacial isostatic adjustment processes like surface uplift/subsidence, changes in the rotation of the Earth, changes in the gravitational attraction due to the ice mass loss etc. Melting of the large ice sheets in both the northern and southern hemispheres after the Last Glacial Maximum led to changing sea levels around the world. However, changes are not uniform, and the different zones are visualized in different colors here, with zones II to V being affected by the dynamics of the glacial forebulge. Credit: Brandes et al. [2025], Figure 13

How have these methods evolved over time?

Today, high-quality sea level data are used in the study of glacial forebulges and the numerical models used to simulate Earth deformation and relative sea level change are more refined and realistic. For example, the change in ice-thickness history and the migration of ice margins for all the globally important ice sheets and their interactions on Earth deformation are included. Earth material properties can now change both radially and laterally. Mantle flow-law can be linear, nonlinear, and composite.

In the computation of sea level change, effects such as time-dependent coastlines (land-sea boundaries that change geographically over time) and rotational feedback (the concept that the redistribution of Earth’s surface and internal mass can change its rotational or spin motion and thus sea levels) are included. Besides sea level data, other measurements from modern geodetic techniques are also used. For example, forebulge decay is inferred from the Global Navigation Satellite System (GNSS).

What are some of the major controlling factors of glacial forebulge behavior/evolution?

The most important controlling factors for the geometry and behavior of a glacial forebulge are the structure and material properties of the lithosphere and the viscosity, as well as the flow pattern, in the underlying mantle (including the asthenosphere). A thick and rigid lithosphere leads to a lower forebulge crest that is located at a greater distance from the ice margin. If the lithosphere is thinner and less rigid, the forebulge crest is higher and lies closer to the ice margin. In addition, the forebulge can migrate through time. The flow behavior of the material in the mantle determines how the forebulge migrates when the ice sheet decays. When the ice melts, the forebulge can either retreat with the ice margin, move away from the ice margin, or decay in place.

Figure 4: Schematic view showing the controlling factors for forebulge evolution. The height and width of the forebulge depends on properties of the lithosphere. A thick lithosphere makes the forebulge lower and further away from the glacier. If the lithosphere is thinner, the forebulge is higher and closer to the glacier. The highest part of the forebulge can migrate through time. The type of material flow in the mantle controls how the forebulge moves when the ice melts. This figure is based on the work of Wu and Peltier [1983], Wu [1993], Kaufmann et al. [1997], O’Keefe and Wu [1998]. Credit: Brandes et al. [2025], Figure 3

What are some of the recent advances in our understanding of glacial forebulges?

GNSS data have allowed researchers to map the position of the now decaying forebulge with a higher accuracy. GNSS data for North America and Europe show that there is a belt of subsidence parallel to the former ice margin. This subsiding area is the decaying forebulge.

In North America, it can be found in the southern parts of the central Canadian provinces and the northern United States, making a north-east turn just south of the Great Lakes, then following the northeastern US east coast states into the Maritimes. In Central Europe, there is a subsidence zone that runs from the Netherlands across northern Germany into Poland and southern Lithuania.

This knowledge about today’s forebulge behavior can help to better predict future sea level positions along the US east coast and the coasts of northern Central Europe, the Baltic countries and southern Scandinavia.

What are the major unsolved or unresolved questions and where are additional research, data, or modeling efforts needed?

Because of its small magnitude today, the forebulge in Europe is difficult to observe. Moreover, there are overlapping processes from sediment compaction and large-scale tectonics that hamper a clear determination with geodetic techniques in northern Central Europe. In northeastern Europe, the forebulge cannot be traced yet because of insufficient geodetic data.

To solve these questions, more high-quality data and improved modeling of glacial isostatic adjustment are needed. An integrated study should interpret all the observations and modeling results related to the glacial forebulge (including, for example, height and direction of bulge movement, uplift pattern, relative sea level changes, stress changes and seismicity, etc.) to get a more coherent view of the glacial forebulge dynamics. Precise terrestrial GNSS measurements and satellite data should be utilized to enhance the understanding of forebulge evolution and help to distinguish its subsidence signal from the subsidence caused by groundwater extraction or natural gas recovery.

—Christian Brandes (brandes@geowi.uni-hannover.de, 0000-0003-2908-9259), Leibniz Universität Hannover, Germany; Holger Steffen (0000-0001-6682-6209), Lantmäteriet, Sweden; Rebekka Steffen (0000-0003-4739-066X), Lantmäteriet, Sweden; Tanghua Li (0000-0003-0501-0155), Nanyang Technological University, Singapore; and Patrick Wu (0000-0001-5812-4928), University of Calgary, Canada

Citation: Brandes, C., H. Steffen, R. Steffen, T. Li, and P. Wu (2025), How glacial forebulges shape the seas and shake the earth, Eos, 106, https://doi.org/10.1029/2025EO255030. Published on 23 September 2025. This article does not represent the opinion of AGU, Eos, or any of its affiliates. It is solely the opinion of the author(s). Text © 2025. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

As the frequency and intensity of heat waves increase across the U.S., a similar but more striking phenomenon is occurring in American rivers.

Is your city prepared for flooding caused by extreme rainfall under climate change? In many regions, the uncertainty surrounding this threat is a major cause for concern and an obstacle to adaptation. However, according to researchers from Japan, their new statistical method increases the accuracy of flood risk projections across about 70% of Earth's landmass.

The Dadiwan Culture, a key representative of China's Neolithic period in the Yellow River Basin and considered one of the origins of the Yangshao Culture, experienced a mysterious 500-year gap between its first and second phases, according to new research.

"Atmospheric rivers" are large-scale extreme weather systems that are making headlines more frequently. When viewed in satellite images, they appear just as described—like rivers in the sky. Though they are often reported in places like California, these weather systems have the potential to bring high heat and dump disastrous amounts of precipitation on areas throughout the mid and high latitudes.