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A multinational scientific team led by UiT has uncovered the deepest known gas hydrate cold seep on the planet. The discovery was made during the Ocean Census Arctic Deep–EXTREME24 expedition and reveals a previously unknown ecosystem thriving at 3,640 meters on the Molloy Ridge in the Greenland Sea. The groundbreaking findings regarding the Freya Hydrate Mounds, which hold scientific significance and implications for Arctic governance and sustainable development, have recently been published in Nature Communications.

A 400-mile blanket of fog has socked in California's Central Valley for weeks. Scientists and meteorologists say the conditions for such persistent cloud cover are ripe: an early wet season, cold temperatures and a stable, unmoving high pressure system.

When it comes to landslides, some of our planet’s largest have occurred underwater. But out of sight shouldn’t mean out of mind—submarine landslides can be both damaging and dangerous.

Researchers have now mapped the Stad Slide, an underwater megaslide that occurred in the Norwegian Sea several hundred thousand years ago. Material raining out of ancient glaciers set the stage for this event, and an earthquake might have been the ultimate trigger, the team surmised. And with a smaller nearby landslide known to have created a significant tsunami, the hunt is on for evidence of the waves that the Stad Slide might have unleashed. These results were published in the Journal of Quaternary Science.

Follow the Chaos

In many places around the world, jumbled layers of sediment lurk beneath the seafloor.

“The next best thing is to map these deposits.”

Such sedimentary chaos is evidence of one or more ancient underwater landslides that occurred on a grand scale. Humans have never witnessed such an event, but these megaslides are apt to damage undersea infrastructure like communications cables and trigger tsunami, said Bridget Tiller, a geographer at Newcastle University in the United Kingdom. By studying what’s left behind, it’s possible to better understand these events and potentially prepare for similar ones in the future, she added. “The next best thing is to map these deposits.”

Tiller and her colleagues recently focused on the Stad Slide, which occurred off the coast of Norway roughly 400,000 years ago. It’s one of at least five landslides that took place in the region over the past 3 million years. But given its hidden nature—the deposits of the Stad Slide lie roughly 1 kilometer beneath the seafloor, which is, in turn, capped by several hundred meters of water—it was first identified just a decade ago. That earlier investigation mapped less than 5% of the Stad Slide’s deposits, however.

Contrasting Sediments

Tiller and her team have now mined observations that cover nearly the entirety of this Switzerland-sized megaslide. Those data were collected from 2014 to 2018 by TGS, a company that amasses geological and geophysical data for energy exploration. The observations are seismic reflection data, meaning that they were generated by launching sound waves downward from a ship-based platform and measuring how those waves were reflected.

These measurements reveal not only the properties of the seabed but also the nature of the sediment layers beneath the seafloor, said Tiller. “Any time there’s a change in the properties of the sediment below the seabed, you can see these different reflections.”

The researchers discovered interspersed layers of sediment, some measuring up to hundreds of meters thick. Those layers appeared to be composed of either coarse material or fine-grained, sand-dominated material. That layering of contrasting sediments likely predisposed the region to sloughing off in a landslide, the team concluded.

The coarser sediments probably built up over time as a result of ancient glacial activity in the region, the team surmised. Glaciers literally scrape the landscape, depositing sediments entrained within them, explained Rob McKay, a sedimentologist at the Antarctic Research Centre at Victoria University of Wellington in New Zealand not involved in the research. “They basically bulldoze a lot of sediment,” said McKay. “In some places, it can be meters per year of sediment coming out.”

The finer, sand-rich sediments naturally accumulated over the eons because of erosion, the researchers found. Those sediments could well contain biological material, added McKay, which might predispose their layers to sliding down the continental shelf. Aquatic microorganisms known as diatoms create slippery mats when they settle out of the water column, and McKay and his team have suggested that such layers could predispose a region to sliding. “That creates a slide plane,” said McKay.

But a trigger of some sort was probably likely to send those layers moving downslope, the researchers concluded. “It wouldn’t fail just on its own,” said Tiller. An earthquake is a likely culprit, the team noted. However, ground movement due to isostatic rebound might also have done it, said McKay.

Stairs Beneath the Seafloor

“We think it formed in multiple stages.”

Tiller and her collaborators inferred that the sediments that composed the Stad Slide failed in several stages. Finding multiple scarps in a kind of stair-step profile indicated that material had let loose sequentially, said Tiller. “We think it formed in multiple stages.”

The current dataset doesn’t reveal anything about how closely in time those failures might have occurred, however, said Tiller. “It could be almost instantaneous, it could be up to several hundred years apart.”

The team estimated that roughly 4,300 cubic kilometers of sediment were displaced by the Stad Slide. That’s roughly 1,000 times the volume of material ejected by the largest volcanic eruption of the 20th century, the team calculated. And all that material in motion would have displaced seawater, potentially resulting in a tsunami.

Another underwater landslide in the area, the much younger Storegga Slide, is known to have produced a tsunami whose waves reached more than 10 meters above sea level. The Stad Slide is about 30% larger by volume than the Storegga Slide, so it’s highly plausible that it too triggered a large tsunami. But finding evidence of waves from that long ago is a tall challenge, said Tiller. “It’s nearly half a million years ago now. It’s possible they wouldn’t have been preserved.”

But don’t give up yet, said McKay, because there’s good evidence for far older tsunamis. In New Zealand, unusual rock outcroppings originally attributed to tectonic activity are now believed to be due to the tsunami waves that rolled up on shorelines 65 million years ago following the dinosaur-killing asteroid impact marking the end of the Cretaceous.

—Katherine Kornei (@KatherineKornei), Science Writer

Citation: Kornei, K. (2025), New eyes on one of the planet’s largest submarine landslides, Eos, 106, https://doi.org/10.1029/2025EO250469. Published on 22 December 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.

This is an audio story from Eos, your trusted source for Earth and space science news. Do you like this feature? Let us know in the comments or at eos@agu.org.

TRANSCRIPT

Emily Gardner: Justin Higa is a geologist, a postdoctoral researcher at the University of Hawaiʻi at Mānoa, where he studies landslides.

But like most of us, he does more than just work. He has hobbies. When he was in high school, he started taking lessons on the sanshin, a three-string lute that has been called “the soul” of the music tradition in the Ryukyu Islands, a chain of southern Japanese islands that include Okinawa. Higa himself is Okinawan, and he wanted to learn more about his culture. So he joined the Ryukyu Koten Afuso Ryu Ongaku Kenkyu Choichi Kai USA, Hawaiʻi Chapter. His instructor was June Uyeunten, or, as he calls her, June Sensei.

At AGU’s Annual Meeting in New Orleans this December, Higa presented research that aimed to bridge the worlds of geoscience and Indigenous Ryukyuan music.

Justin Higa: This started because when I was an undergrad at the University of Hawaiʻi, there was a lot of focus on place-based science and Indigenous Knowledge and Hawaiian knowledge in geology. So because of this background in the arts that I had, and I knew that we’d sung songs about nature and animals and plants, I thought, “Oh, you know, we could do similar things with the songs that we sing and interpret science from lyrics.”

Gardner: Higa went to California for grad school, but when he came back to Hawaii for his postdoc, he had a little more freedom to pursue different research interests, and he was back in a place with a strong Okinawan diaspora presence. Maybe he could use this music to teach the public, and people interested in music, about the geosciences. His mentor, Uyeunten, was excited for the inverse reason: Maybe this could be a way to get the public, and scientists, interested in Ryukyuan music.

June Uyeunten: I got superexcited, cause I’m like, if Justin can get that excitement out into the public, maybe we can tap other people who are not interested in this type of music to learn more about it, right? And so you don’t know which audience we’re going to appeal to. And so we just have to try different ways to educate others. And music is universal. You don’t need to understand the lyrics, but you could feel it when a performer sings it, right? 

Gardner: Higa teamed up with Uyeunten and Kenton Odo, who are both instructors in the same chapter, to look at how Indigenous Ryukyuan music could be used to teach about geoscience and the climate.

They focused their analysis on a pair of sailing songs, both composed in the 18th century. One is called “Nubui Kuduchi”; Kuduchi is a subgenera of Ryukyuan classical music. And nubui means “climbing up.” The song starts with a description of a group of envoys walking from the Ryukyu capital to the main port on Okinawa, stopping at temples along the way to pray, and then saying goodbye to their families. Then, they set sail to the Kyushu islands:

 (sample of “Nubui Kuduchi” plays)

The lyrics here say, “Sailing across the rough seas off the coast of Iheya, we look out over the route of many islands. To see the Tokara Islands and Strait, and pass without mishap. How lucky we are.”

The south-southwesterly winds described in the song, taking place between May and September, match with observations from the 20th and 21st centuries, which have documented the same wind patterns at the same time of year. The researchers further looked at historical records, which showed that during this period of history, about 20 such envoy departures took place each year between approximately May and August. It all lined up perfectly.

They also analyzed another song called “Kudai Kuduchi.” Kudai means “climbing down.” In this song, the envoy returns to Okinawa island via north-northeasterly winds.

 (sample of “Kudai Kuduchi” plays)

The lyrics here say, “The winds are directly from the north-northeast, with Cape Sata behind us. Sailing comfortably over the seas of the Tokara Islands and Strait.”

Once again, it all lines up: The northeasterly boreal winter monsoon typically occurs from September to May, and historical records show the envoys returning to port at that time of year.

Higa: We could make implications and a discussion about how this kind of implies a reliance on a very constant monsoon season for travel, and when that breaks down, that’s a problem for them. 

Gardner: In another line, the sailors observe an active volcano.

Higa: It’s kind of cool in that this volcano that they observed as active during their boat journey, it was kind of in a location that’s a little outboard from the main Japanese islands that had a lot of written historical records.

So maybe the earliest record was from, I think the 12th century, and then we have our song from the 18th century and then modern instrumented science. So it’s these three points of volcanic activity and ours is kind of bridging that in the middle, kind of implying that, yeah, this volcano has been active for continuously for a very long time and that aligns with geochronologic dating, geologic mapping of this area.

Gardner: James Edwards is an ethnomusicologist at the SINUS Institute, an institution for market and social research in Germany. He wrote his dissertation on the Okinawan performing arts, tracking its development from the 17th century to today. He focuses in part on ecomusicology, a field that examines, among other things, how music mediates the relationships between humans and the environment.

Edwards was not involved in this work, but he said the project was really interesting and could be a launching point for potential interdisciplinary collaboration.

James Edwards: Traditional ecological knowledge can be a valuable intervention contra the overreach of Western scientism and the privileging of Western knowledge systems, right? In this case, you have the opposite. You have a traditional ecological system and Western scientific knowledge synergizing and complementing each other in a really beautiful way.

Gardner: On top of the research presented at AGU25, the authors have published a paper about their work in Geoscience Communication and shared the work in the science and art worlds, including at the Geological Society of America conference and an Okinawan festival in Hawaii. September of 2025 marked 125 years since the first Okinawan immigrants arrived in Hawaii. Especially during such a landmark year, Higa and Uyeunten have high hopes for the work. Incorporating such music into science lessons, for instance, could help educators demonstrate the value of Indigenous Knowledge throughout history.

Uyeunten: If you can blend your career with your culture and with some art form, I think that’ll just, you know, be a good thing to just broaden everyone’s lenses.

Higa: I guess it, I hope it really shows the legitimacy of Indigenous Knowledge from all cultures and it inspires other people to….think of themselves as you can be a scientist and you can be an artist.

Reading List

Paper in Geoscience Communication: Place-based science from Okinawa: 18th-century climate and geology recorded in Ryukyuan classical music

AGU25 abstract: Transforming Indigenous Ryukyuan Music into Geo- and Climate Science Lessons for the Ryukyuan-Okinawan Diaspora in Hawaiʻi

Ryukyu Koten Afuso Ryu Ongaku Kenkyu Choichi Kai USA

University of Hawaiʻi press release

(“Kudai Kuduchi” fades in)

Gardner: Thank you to Justin Higa and June Uyeunten for speaking with me and to their coauthor, Kenton A. Odo. All are members of Ryukyu Koten Afuso Ryu Ongaku Kenkyu Choichi Kai USA, Hawaiʻi Chapter. Thank you also to James Edwards for providing an outside perspective. Credits for the music are as follows:

Translation and interpretation: Hooge Ryu Hana Nuuzi no Kai Nakasone Dance Academy, Clarence T. Nakosone

Singing and Sanshin by Kenton Odo

Tēku (the drums) and fwansō (the bamboo flute) by June Uyeunten

Thanks for listening to this story from AGU’s Eos, your source for Earth and space science news. As always, you can find a transcript of this story, as well as links to the relevant research, at Eos.org.

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

Citation: Gardner, E. (2025), What Okinawan sailor songs might teach us about the climate, Eos, 106, https://doi.org/10.1029/2025EO250486. Published on 22 December 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.

A swarm of at least a dozen earthquakes reaching up to magnitude 3.9 rattled San Ramon near San Francisco, the U.S. Geological Survey reports.

SummaryThis study develops a Bayesian optimisation method of coseismic slip distributions and the correlation lengths of the von Kármán autocorrelation function, which can realize more reliable regularisation grounded in geophysical analysis (VKR). To validate VKR and its dependence on the observation, synthetic tests using data from inhomogeneously distributed Global Navigation Satellite System (GNSS) stations and Synthetic Aperture Radar (SAR) were conducted. When observation stations surround the source fault, the assumed slip distribution and the correlation length were well recovered with some artificially extended slip due to the inhomogeneity of the observation network. Moreover, when observation stations exist only on one side of the fault, the method recovered the slip and other parameters with accuracy comparable to that of the surrounding-case scenario, albeit with slightly increased uncertainty of the parameters. This highlights the importance of uncertainty evaluation for slip and correlation length parameters, especially under biased observation networks. Applying existing Laplacian smoothing methods to the same experiments produced models globally consistent with VKR, demonstrating that the proposed method, despite additional non-linear parameters, achieves comparable estimation accuracy. Existing method showed isotropic correlations of slip variables, whereas VKR exhibited correlations elongated along the strike direction, reflecting its ability to independently regularise along strike and dip via correlation length parameters. These correlation patterns were most pronounced in deeper fault regions, where regularisation dominated over observational constraints. Cluster analysis of the Markov samples revealed that VKR captured a more diverse set of slip distribution models, with cluster differences most evident in deeper fault regions. These analyses underscore the importance of regularisation choice and its impact when evaluating and interpreting slip distributions. We also applied VKR to the actual data of the 2024 Noto Peninsula earthquake in Japan, observed by dense GNSS networks and SAR. The estimated slip distribution featured multiple slip areas in the eastern and western peninsula, consistent with previous studies and Laplacian smoothing-based results. The correspondence between estimated slip distribution and correlation length was confirmed, although it did not match previous empirical findings. To further examine the effect of observation network configuration, we performed additional inversions using a reduced set of actual data. The resulting slip distribution was smoother, and the estimated correlation lengths were larger and more uncertain. Our results reconfirm that simultaneous estimation of slip distribution and correlation length produces mutually consistent values, both of which depend on the spatial distribution of observation points. The results also demonstrate the strong dependence of estimated slip distribution and correlation lengths on the observation network. Therefore, future studies of coseismic slip self-similarity, using observed data, should incorporate parameter analyses that account for network resolution effects.

SummaryThe precise extraction of tidal signals from non-stationary gravity observations is a central challenge in geophysics, where accuracy is often limited by mode mixing in data preprocessing algorithms. This study evaluates the performance of the Time-Varying Filter-based Empirical Mode Decomposition (TVF-EMD) method to address this issue. We employed a progressive validation pipeline: the method was first verified on simulated signals, then rigorously tested against a high-fidelity benchmark from a superconducting gravimeter (SG), and finally applied to one month of continuous data from an Atom Gravimeter (AG) at the Yilan station. Results demonstrate that TVF-EMD dramatically suppresses mode mixing, with the energy of transient spikes in its residual being an order of magnitude lower than that from the conventional Ensemble Empirical Mode Decomposition (EEMD) method. The tidal signal reconstructed by TVF-EMD achieved the highest cross-correlation coefficient and the smallest root mean square error when compared to the theoretical gravity tide. Subsequent harmonic analysis confirmed that TVF-EMD yielded the lowest errors across all major tidal constituents. These findings validate TVF-EMD as a superior preprocessing framework for tidal analysis, particularly for enhancing the reliability of geophysical parameter inversion from short-duration records obtained with next-generation quantum sensors.

SummaryStructural boundaries are often the features of most interest geologically, but imaging them can be difficult due to wavefield scattering and interference caused by the sharp velocity contrasts. One example of this is the apparent Rayleigh-wave anisotropy (1-psi anisotropy) that has been observed near major structural boundaries using seismic arrays. The cause of the apparent anisotropy is the interference between the incident surface wave and waves scattered from velocity discontinuities. In this study, we first investigate the sensitivity of apparent anisotropy measurements to lateral boundary sharpness through 2D full waveform simulations. We demonstrate that 1-psi anisotropy can vary based on boundary sharpness, station spacing, and period of surface waves. We show that a misfit defined using triple-difference travel times, i.e. the difference in double-difference travel times between station pairs with opposite propagation directions, well characterizes the apparent anisotropy. The sensitivity kernel for this triple-difference misfit can be constructed using the adjoint method. We show that triple-difference travel times are mainly sensitive to velocity contrasts rather than absolute velocities, in contrast to double-difference travel times. With sensitivity kernels constructed, we demonstrate how triple-difference travel times can be combined with double-difference travel times into a tomography inversion. We show that by including triple-difference travel times, seismic inversions converge faster and resolve boundary and average structure better in early iterations, compared to using double-difference travel times alone. Recent advancements in dense array experiments could facilitate the application of this method to better delineate tectonic and basin structural boundaries.

"Kablooey!" That's the word U.S. Geological Survey volcanic experts used to describe a muddy eruption at Black Diamond Pool in Yellowstone National Park on Saturday morning.

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