EOS

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

What better way to study an entire planet’s monthly exchange of CO2 between the atmosphere, oceans, and land than to position a satellite in space that measures these swings in the atmosphere’s CO2 on a daily basis? We’ve had that tool, NASA’s Orbiting Carbon Observatory-2 (OCO-2), since 2014, and it has yielded an impressive body of science, demonstrating the impacts of natural and human-induced changes in emissions and sinks of CO2, including large-scale fires, ocean warming, and the economic shutdown during the COVID-19 pandemic.

The monthly growth rate of global atmospheric CO2 (ppm yr-1) measured by the OCO 2 satellite‐ (black line) demonstrates a relationship with the Earth’s global surface temperature increase (relative to the preindustrial baseline; red dashed line). The fossil CO2 emissions (black dashed line) are interpolated annual values (also expressed as ppm yr-1), which dipped during the pandemic of 2020, but have resumed growing since then. Credit: Pandey [2025], Figure 1a

In addition to unprecedented frequency of global CO2 measurements, it also provides spatial resolution that enables attribution to changes of sources and sinks across latitudes and continents. This science is driven, in part, by concerns about climate change, but even if we take climate out of the equation to remove political implications, the basic science of understanding the Earth’s carbon cycle has advanced tremendously by this extraordinary tool in space.

Pandey [2025] likens the possible premature decommissioning of this satellite to removing stethoscopes from medical doctors’ toolkits, and yet that is precisely what the current U.S. Administration’s proposed 2026 budget would do. This commentary elegantly describes what has been learned from the OCO-2 mission and how it can inform policy; it should be mandatory reading for anyone, from members of Congress to their constituents, who could possibly influence funding for the OCO-2 mission.

Citation: Pandey, S. (2025). Taking Earth’s carbon pulse from space. AGU Advances, 6, e2025AV002085. https://doi.org/10.1029/2025AV002085

—Eric Davidson, Editor, AGU Advances

Text © 2025. The authors. CC BY-NC-ND 3.0
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Successfully predicting earthquakes sounds like a dark art.

However, new research hints it may be possible: Sediment cores extracted from the Pacific seafloor suggest that two major fault systems along the western coast of the United States and Canada might be partially synchronized. After an earthquake on the southern part of the Cascadia subduction zone, an earthquake soon after on the northern part of the San Andreas fault appears to occur roughly half of the time, the new findings reveal. These results, published in Geosphere, provide evidence of stress triggering, which has long been invoked to explain how activity on one fault might lead to activity on another nearby.

Fault zones persist across wide swaths of our planet, but the one that stretches onshore and offshore from California to British Columbia, Canada, is particularly complex. The vertical strike-slip San Andreas fault, in the south, intersects the Cascadia subduction zone off the coast of Northern California at a point known as the Mendocino Triple Junction.

There’s an amalgam of different types of large, active faults, and the Mendocino Triple Junction itself is migrating northward, said Chris Goldfinger, an earthquake geologist at Oregon State University in Corvallis. “It’s a very complicated situation.”

Earthquake Here, Earthquake There

Researchers have long wondered whether the northern region of the San Andreas fault and the southern part of the Cascadia subduction zone might be affecting one another. The idea isn’t far-fetched: Scientists know that earthquakes, which result from sudden releases of stored-up energy on a fault, relieve stress on one part of a fault but often do not make that stress disappear. “When it ruptures, [a fault] relieves the local stress. But then it transfers stress to other things around it,” said Goldfinger. Such stress transfer could, in turn, trigger activity on another nearby fault.

In 2008, Goldfinger and his colleagues published a study of earthquakes along the northern San Andreas and Cascadia subduction zone. To determine when the earthquakes happened, the team used radiocarbon dating of turbidites, which are sedimentary deposits left on the seafloor when ground shaking causes underwater landslides. The researchers found several apparent pairs of earthquakes that seemed to have occurred around the same time—that is, within decades or centuries of one another. However, the significant age uncertainties precluded drawing any definitive conclusions about paired earthquakes, Goldfinger said.

Mysterious Turbidites

Since then, Goldfinger and his collaborators have obtained more turbidite records from sediments in the ocean and also analyzed inland sediments from places like Lake Merced near San Francisco. With those new data, which stretch back roughly 3,100 years, in hand, the team returned to the question of paired earthquakes. The researchers also revisited a mystery that had been bothering them since the late 1990s: Why did some turbidites collected from near the Mendocino Triple Junction appear to be upside down?

“They had all of the sand at the top, which is not where it should be.”

Turbidites are layers of sand, mud, clay, and silt that typically are coarsest near the bottom and become finer grained at the top. That’s because gravity causes the coarsest particles—the sand—to settle out first and smaller particles to be deposited later as the current slows down. But many of the turbidite beds recorded in cores from near the Mendocino Triple Junction appear to be capped with sand, rather than finer sediment. That’s unexpected, said Goldfinger. “They had all of the sand at the top, which is not where it should be.”

It’s taken more than 2 decades for the team to finally arrive at an explanation for those anomalous turbidites.

They are, in fact, two turbidite beds, Goldfinger and his colleagues concluded. The sand on top is actually a second turbidite bed formed close to an earthquake source whose finer particles were carried away and deposited at more distant locations.

The researchers furthermore inferred that these so-called doublet turbidites were created by two different earthquakes occurring on different fault systems—one in the Cascadia subduction zone and one on the San Andreas fault. The tip-off was that the occurrence of doublet turbidites systematically decreases with increasing distance from the Mendocino Triple Junction. The San Andreas–derived turbidite beds fade away to the north, and Cascadia-derived turbidite beds fade away to the south. That’s expected because shaking from San Andreas earthquakes will be weaker the farther north one goes and shaking from Cascadia earthquakes will correspondingly be weaker the farther south one goes.

“These doublets should fade in a specific way, and they do,” said Goldfinger.

The team found that slightly more than half of the 18 turbidites they studied in the southern Cascadia subduction zone were closely associated in time with turbidites from the northern San Andreas. In those 10 cases, the median ages of the earthquakes inferred from radiocarbon measurements differed from their associated quake on the other fault system by roughly 60 years, which is about equal to the data’s uncertainty. Eight of those pairs furthermore exhibited a doublet structure, indicating that they occurred especially close together in time.

The similar timing and unique stacking pattern of the doublets suggest that Cascadia earthquakes generate regional stresses that trigger subsequent earthquakes on the northern San Andreas fault.

These findings convincingly demonstrate that the northern San Andreas and the southern Cascadia subduction zone are at least partially synchronized, said Kathryn Materna, a geophysicist at the University of Colorado Boulder not involved in the work. “Seeing half of them correlated on opposite sides of the triple junction is a pretty striking correlation,” she said. Because these faults tend to unleash earthquakes at different rates, there’s no reason their events should line up closely in time, said Materna. “They’re different systems with different recurrence intervals.”

Patiently Ducking and Covering

“The best fit to the data, by far, is to have Cascadia go first.”

Goldfinger and his colleagues believe that in cases of paired earthquakes, Cascadia is the one leading the charge. “The best fit to the data, by far, is to have Cascadia go first,” said Goldfinger.

Understanding why will take some modeling work. It’d also be interesting to dig into whether a Cascadia event of a certain magnitude is necessary to unleash shaking on San Andreas, he said. “It makes sense that there must be a triggering threshold.”

These findings suggest that a large Cascadia earthquake might be followed by ground shaking on the San Andreas. But ducking and covering after Cascadia lets loose could require some patience. The timing between paired earthquakes likely varies substantially, Goldfinger said. “It could be anything from minutes to decades.”

—Katherine Kornei (@KatherineKornei), Science Writer

Citation: Kornei, K. (2025), When Cascadia gives way, the San Andreas sometimes follows, Eos, 106, https://doi.org/10.1029/2025EO250419. Published on 12 November 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.

In 2008, NASA’s now-departed Cassini spacecraft made its fastest flyby of Enceladus, the moon of Saturn that’s spewing its subsurface ocean into space. A new analysis of data from that flyby has revealed a bevy of complex organic compounds that hadn’t been detected before and confirmed the origin of several previously known organics. The speed at which the flyby occurred, a zippy 18 kilometers per second, helped convince the researchers that the organics truly originated from Enceladus’s interior ocean and were not a product of postejection space weathering.

When combined with the slate of previously detected organic compounds, “these new organics could support chemical networks or chemical pathways that potentially could lead to biologically relevant compounds,” said Nozair Khawaja, lead researcher on this discovery and a planetary scientist at Freie Universität Berlin in Germany.

Connecting Chemistries

Enceladus emits plumes of water from its subsurface ocean through icy cracks near its south pole. Enough material has been released into space to create a ring around Saturn called the E ring. During its 13 years exploring the Saturn system, Cassini collected and analyzed multiple samples from the E ring and discovered a wide variety of organic and inorganic molecules, including aromatics and oxygen-bearing species, that hinted at complex chemistry happening within Enceladus.

“If you capture some particles in the E ring, that means, indirectly, you are sampling the subsurface ocean.”

“If you capture some particles in the E ring, that means, indirectly, you are sampling the subsurface ocean,” Khawaja said.

However, planetary scientists have debated whether all of the organic compounds discovered in E ring material could truly be traced back to the Enceladean ocean. After all, material sits in the E ring for years, and the material’s chemistry may have been altered through exposure to radiation from Saturn and the solar system, a process called space weathering.

Material ejected from Enceladus creates Saturn’s E ring, imaged here by Cassini in 2006. Credit: NASA/JPL/Space Science Institute

But Cassini didn’t just fly through Saturn’s rings. It also flew directly through Enceladus’s plumes. During those flybys, the spacecraft’s onboard Cosmic Dust Analyzer (CDA) collected and measured spectra from freshly ejected material. Grains of material entered the CDA collector and shattered into chemical constituents—mostly water ice with smatterings of other molecules. The CDA measured chemical spectra and reported what those grains were made of.

The trouble is that water molecules are very sticky, Khawaja explained. After shattering, ice molecules quickly cluster around and shield other molecules from detection. The slower the grains traveled through the instrument, the less time CDA had to spot those other compounds, which were the ones that scientists were most interested in decoding.

Previous analyses of Enceladus and E ring flybys, most of which occurred at relative speeds less than 12 kilometers per second, detected five of the six elements essential for Earth’s biology—the CHNOPS elements—but other materials remained elusive.

Speed Is Everything

Luckily, Cassini’s fifth Enceladus flyby was particularly speedy. Plume material traveled through the CDA at 18 kilometers per second. Analysis of data from that flyby, conducted by Khawaja and his team, revealed that the freshly ejected ice grains contained many of the same compounds that had previously been found in E ring material.

New models suggest that organic molecules could originate in hydrothermal vents at the base of Enceladus’s ocean, float upward toward the bottom of the moon’s ice shell, and condense onto ice grains as they travel through vents, before being ejected into space. Credit: NASA/JPL-Caltech

“These new particles, they were very young in age and very fresh material,” Khawaja said. “That means, if we observe in these fresh grains the same compounds [seen] in the E ring grains, which are months or many years old, that means that those compounds are actually coming from the subsurface of Enceladus.”

Because the material collected in this flyby did not have time to be altered by space radiation, these chemical commonalities “effectively rule out” space radiation or another process external to Enceladus as the source of complex organic material in the E ring and Enceladus’s ocean, explained Alexander Berne.

The results “indicate that endogenic processes, such as hydrothermal activity, i.e., energy-releasing interactions between silicate rock and water, form the observed chemistry,” Berne said. “This hydrothermal activity is potentially a key process for sustaining metabolic reactions to support astrobiology within Enceladus,” like black smokers near Earth’s mid-ocean ridges. Berne, a planetary scientist at the California Institute of Technology in Pasadena, was not involved with this research.

New Ingredients in the Soup

The swiftness of this particular flyby also enabled the CDA to measure the spectra of several previously undetected complex organic compounds before they were shielded behind an icy curtain. These compounds, including oxygen- and nitrogen-bearing species, aryls, alkenes, and ethyls, strengthen the theory that they were generated through geochemical processes at the base of the Enceladean ocean.

“The new compounds confirm that organics are present in the subsurface ocean and may indicate more complex, potentially hydrothermal processes there,” said Larry Esposito, a planetary scientist at the University of Colorado Boulder who was not involved with this research. “The new findings are consistent with the likely habitability of the ocean, which may resemble a complex organic ‘primordial soup.’”

These results were published in Nature Astronomy in October.

Khawaja cautioned that these newly detected organics do not mean that life exists in Enceladus’s ocean or that life is an inevitable result of mixing together this primordial soup. Continued analysis of archival Cassini data, bolstered by future laboratory experiments, could reveal the many potential outcomes of this chemical mixture and could piece together its origin story.

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

Citation: Cartier, K. M. S. (2025), Speedy flyby adds new organics to Enceladus’s “primordial soup,” Eos, 106, https://doi.org/10.1029/2025EO250416. Published on 12 November 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.

In August 2025, I recorded 104 fatal landslides leading to 2,365 fatalities, a record total number of landslides for August.

Loyal readers will know that each year, August is one of the two peak months for fatal landslides. In 2025, I recorded 104 fatal landslides leading to 2,365 fatalities (but please see below as I have severe doubts about the latter number).

This is an unusually high level of loss both in terms of the number of fatalities and the number of events.

This is the monthly total number of landslides for 2025 to the end of August:-

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

Loyal readers will also be aware that I like to use pentads (five day blocks) for inter-annual comparisons. This is the 2025 plot to pentad 49 (2 September 2025):-

The number of fatal landslides to 2 September 2025, displayed in pentads. For comparison, the long term mean (2004 to 2016) from Froude and Petley (2018) and the exceptional year of 2024 are also shown.

The graph demonstrates that to the end of August, 2025 was running a very long way above the long term mean number of landslides, and indeed was close to the absolutely exceptional number recorded in 2024.

The number of fatal landslides in August 2025 was dominated by events in South Asia, and in particular in India. That will need further analysis in due course. In terms of fatalities, the total was driven by the 31 August 2025 landslide at Tarasin in Sudan, which is reported to have killed 1,573 people. However, as I noted in a blog post, I have severe doubts about this total. At this stage, I do not have a reliable alternative total, so I have included the number as reported locally.

In terms of the number of fatal landslides, 2025 had the highest August total in my dataset. The previous highest total was 78 in 2018.

August 2025 was the third warmest August globally in the instrumental record, but it was cooler than both 2023 and 2024. In this case, it appears that the rainfall pattern from the summer monsoon in South Asia has had a major impact.

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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A weak spot in Earth’s protective magnetic field is growing larger and exposing orbiting satellites and astronauts to more solar radiation, according to more than a decade of measurements by three orbiting observatories.

“The region of weak magnetic field in the South Atlantic has continued to increase in size over the past 11 years.”

The observations by the European Space Agency’s Swarm trio of satellites found that Earth’s already weak magnetic field over the South Atlantic Ocean—a region known as the South Atlantic Anomaly (SAA)—is getting worse and that it has grown by an area half the size of continental Europe since 2014. At the same time, a region over Canada where the field is particularly strong has shrunk, while another strong field region in Siberia has grown, the measurements show.

“The region of weak magnetic field in the South Atlantic has continued to increase in size over the past 11 years since the launch of the Swarm satellite constellation,” explained Chris Finlay, a geomagnetism researcher at the Danmarks Tekniske Universitet. “Although its growth was expected based on early observations, it is important to confirm this change in Earth’s magnetic field is continuing.” Finlay is the lead author of a new study published in the journal Physics of the Earth and Planetary Interiors that analyzes data from the Swarm satellites.

Geomagnetic Field

The three satellites were launched in 2014 to precisely monitor magnetic signals from Earth’s core and mantle, as well as from the ionosphere and magnetosphere. Earth’s magnetic field (technically, the “geomagnetic field”) is thought to be generated by a rotating core of molten iron, roughly 2,900 kilometers, or 1,800 miles, beneath our feet. But the strength of the field changes continuously, and scientists are still learning about its exact mechanisms.

“Satellites experience higher rates of charged particles when they pass through the weak field region…astronauts will also experience these charged particles.”

The geomagnetic field protects life on Earth’s surface from harmful charged particles in solar radiation. We can see the effects of charged particles from the Sun interacting with the geomagnetic field in the upper atmosphere during aurorae such as the northern lights.

And because it extends into space, the geomagnetic field also protects orbiting spacecraft, including most satellites and the International Space Station (ISS). However, the study authors warn that spacecraft—and spacefarers—that enter the South Atlantic weak spot during their orbits of our planet could now be exposed to more radiation.

For spacecraft hardware, this radiation could cause more malfunctions, damage, or even blackouts. “The main consequence is for our low-Earth-orbit satellite infrastructure,” Finlay said. “These satellites experience higher rates of charged particles when they pass through the weak field region, which can cause problems for the electronics.”

Danger to Astronauts

People in orbit will also face higher risks from radiation, including a greater chance of DNA damage and of suffering cancer during their lifetimes. “Astronauts will also experience these charged particles, but their times in orbit are shorter than the lifetime of most low-Earth-orbit satellites,” Finlay said. (On average, astronauts on the ISS spend about 6 months in low Earth orbit, but satellites typically spend more than 5 years there—about 10 times as long.)

The geomagnetic field is relatively weak compared with more familiar forms of magnetism: Its intensity ranges from about 22,000 to 67,000 nanoteslas. In comparison, a typical refrigerator magnet has an intensity of about 10 million nanoteslas.

In the SAA, the geomagnetic field’s intensity is lower than 26,000 nanoteslas. According to the study, the region’s area has grown by almost 1% of the area of Earth’s surface since 2014. The weakest point in the SAA now measures 22,094 nanoteslas—a decrease of 336 nanoteslas since 2014.

In the region of strong geomagnetic field over northern Canada, the intensity is greater than 57,000 nanoteslas. The study found that the area has shrunk by 0.65% of the area of Earth’s surface, while its strongest spot has fallen to 58,031 nanoteslas, a drop of 801 nanoteslas since 2014. In contrast, a strong field region in Siberia has grown in size, increasing in area by 0.42% of Earth’s surface area, with the maximum field intensity increasing by 260 nanoteslas since 2014 to 61,619 nanoteslas today.

Scientists have discovered that the weak region in Earth’s magnetic field over the South Atlantic—known as the South Atlantic Anomaly—has expanded by an area nearly half the size of continental Europe since 2014. Credit: ESA (Data source: Finlay, C.C. et al., 2025)

These changes in the Northern Hemisphere were unexpected, Finlay said. “It is related to the circulation patterns of the liquid metal in the core, but we are not certain of the exact cause,” he said.

The study did not, however, find any sign of an impending magnetic field reversal. Earth’s magnetic field has already reversed hundreds of times, but “we know from paleomagnetic records that Earth’s magnetic field has weakened many times in the past, displaying weak field regions like the South Atlantic Anomaly, without reversing,” Finlay said. “We are more likely seeing a decade to century timescale fluctuation in the field.”

“Hardened” Spacecraft

The heightened danger from solar radiation to satellites and astronauts passing over the SAA could be mitigated by ensuring that spacecraft are “hardened” to withstand it, Finlay said: “Since the weakness is growing, the satellites will experience such effects over a larger area, [so] this should be taken into account when designing future missions.”

Geophysicist Hagay Amit of Nantes Université in France, who wasn’t involved in the latest study but who has studied the SAA, noted that several scientists have proposed possible reasons for the observed changes in the geomagnetic field, but the actual mechanisms remain unknown. “Overall, [the authors] convincingly demonstrated that continuous high-quality geomagnetic measurements are crucial for providing vital insights into the dynamics in the deep Earth,” he told Eos in an email.

—Tom Metcalfe (@HHAspasia), Science Writer

Citation: Metcalfe, T. (2025), A weak spot in Earth’s magnetic field is going from bad to worse, Eos, 106, https://doi.org/10.1029/2025EO250417. Published on 10 November 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.

Source: Geophysical Research Letters

The way clusters of differently sized water droplet populations are distributed within clouds affects larger-scale cloud properties, such as how light is scattered and how quickly precipitation forms. Studying and simulating cloud droplet microphysical structure is difficult. But recent field observations have provided crucial, centimeter-scale data on cloud droplet size distributions in stratocumulus clouds, giving researchers an opportunity to better match their models to reality.

The simulations of characteristic droplet size distributions that those models are providing are likely too uniform, say Allwayin et al. This muddled microphysical structure could be leading cloud simulations, and the climate models that use them, astray.

The authors compare the new observed data on cloud microphysical structure with results from large-eddy simulations (LES) of stratocumulus clouds. At convective scales, the model showed intriguing correlations between droplet cluster characteristics and overall cloud physics. For example, regions of the clouds dominated by drizzle tended to have larger drops but not necessarily more total water content, and the updraft regions of clouds tended to have smaller drops and a narrower distribution of droplet size.

However, across larger spatial scales, the characteristic droplet size distributions in the model looked very similar across different parts of a cloud. This diverges sharply from the observations, which show that the size distributions vary across large-eddy scales within the cloud.

One explanation could be that the process of entrainment—in which drier air is introduced into a cloud and causes evaporation—is not well resolved in these models, the authors say, noting a relationship between observations of characteristic droplet size distributions and local entrainment rates. In addition, models often assume that boundary layer properties such as surface fluxes and aerosol types are uniform across clouds.

The authors argue that a better understanding of cloud microphysics and its link to entrainment and boundary fluxes is needed to advance atmospheric modeling. The LES runs in this study are idealized cases, the researchers add, which should be kept in mind when interpreting their results. Future work should focus on understanding the role of horizontal gradients in aerosol concentrations, as well as on improving model entrainment layers, the authors suggest. Lagrangian schemes in LES models could hold more promise for this work. (Geophysical Research Letters, https://doi.org/10.1029/2025GL116021, 2025)

—Nathaniel Scharping (@nathanielscharp), Science Writer

Citation: Scharping, N. (2025), Understanding cloud droplets could improve climate modeling, Eos, 106, https://doi.org/10.1029/2025EO250420. Published on 10 November 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.

The Landslide Blog is written by Dave Petley, who is widely recognized as a world leader in the study and management of landslides.

According to Wikipedia, Pikillaqta is a large archaeological site located 20 km to the east of Cusco in Peru. Inhabited by the Wari people, it was abandoned at about 900 AD for reasons that have not been clear. At the point of abandonment, the site was incomplete, with several key buildings still being under construction. Thus, there has been considerable speculation as to why the site was left by the Wari people.

This area of Peru has a high level of seismic hazard. In the historical record, major earthquakes occurred in 1650, 1950 and 1986 in the immediate area. In a paper just published in the journal Geoarchaeology, Garcia et al. (2025), explore the hypothesis that the abandonment of Pikillaqta might be associated with earthquakes and a landslide at the site. Note that, although the paper is behind a paywall, the link should provide access for all.

The image below shows the site in 2017 – note the scarp to the northeast of the site:-

Google Earth image from 2017 showing Pikillaqta (note the different spelling on Google Earth), and the projected source of the debris flow.

A large part of Garcia et al. (2025) focuses on documenting so-called Earthquake Archaeological Effects at Pikillaqta – these are pieces of evidence in the archaeological record of past earthquake events. They have found 149 pieces of evidence, such as collapsed walls, and they infer from the orientations of these that they record the impacts of two large earthquakes (one between 856 and 988 CalAD and one between 770 and 900 CalAD) that have been identified from palaeoseismological studies of local faults.

But interestingly, Garcia et al. (2025) have also investigated a geological deposit, up to 3 m deep, in and around some of the buildings. This has the sedimentological characteristics of a debris flow, and it contains a fragment of an animal bone that has been dated to 766–898 cal AD. They have then used a high resolution digital elevation model to map the debris flow deposit. They have concluded that it initiated from the scarp to the northeast (see the label on the the Google Earth image) and then flowed through parts of Pikillaqta.

Radiocarbon dating is not precise, so this debris flow could have been triggered by an earthquake, or it could have been associated with exceptional rainfall (or a combination of the two, of course). But there is little doubt that the earthquakes and the landslide caused substantial damage to the site at about the time of abandonment, even when construction was ongoing.

The authors recognise that this is an unproven hypothesis, and encourage further research. But it is deeply fascinating to see how earthquakes and landslides may have shaped the events at this key archaeological site.

Reference

García, B., C. Benavente, M. Á. Rodriguez-Pascua, et al. 2025. Prehistoric Evidence of Crustal Earthquakes and Debris Flow in Archaeological Site of Pikillaqta in Cusco: Archaeological Implications. Geoarchaeology  40: 1-14. https://doi.org/10.1002/gea.70033.

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