Geology topics

Antoine S. Lucas

Publications and source records attributed to Antoine S. Lucas.

3 recordsLinked to original sources

USGS2026

Frictional weakening in the highly mobile 2025 Blatten rock and ice avalanche in Switzerland

Cascading slope failures are increasing as glaciers retreat and slopes adjust to a warming climate, yet reconstructing their full dynamics from precursor to deposition remains challenging. Here we show that the 28 May 2025 Blatten rock-ice avalanche, which mobilized about 9.3 million cubic metres, can be reconstructed from seismic, geomorphological, and geotechnical evidence and numerical modeling. The observations reveal the timing, source, volume, and friction of over two weeks of accelerating rockfalls and minor glacier collapses before the main failure, followed by four stages of avalanche motion. Only with drastically reduced friction can both depth-averaged and three-dimensional models reproduce the center-of-mass force history and the deposit distribution. These friction values reflect effective frictional weakening. Geotechnical observations suggest that transient excess pore pressures possibly contributed to this weakening, but are insufficient to rule out additional mechanisms such as ice frictional reduction, segregation, and fragmentation. This work provides a reproducible and robust framework for analyzing catastrophic avalanches under a changing climate.

Birch Glacier↗

USGS2024

A rockslide-generated tsunami in a Greenland fjord rang Earth for 9 days

Climate change is increasingly predisposing polar regions to large landslides. Tsunamigenic landslides have occurred recently in Greenland (Kalaallit Nunaat), but none have been reported from the eastern fjords. In September 2023, we detected the start of a 9-day-long, global 10.88-millihertz (92-second) monochromatic very-long-period (VLP) seismic signal, originating from East Greenland. In this study, we demonstrate how this event started with a glacial thinning–induced rock-ice avalanche of 25 × 106 cubic meters plunging into Dickson Fjord, triggering a 200-meter-high tsunami. Simulations show that the tsunami stabilized into a 7-meter-high long-duration seiche with a frequency (11.45 millihertz) and slow amplitude decay that were nearly identical to the seismic signal. An oscillating, fjord-transverse single force with a maximum amplitude of 5 × 1011 newtons reproduced the seismic amplitudes and their radiation pattern relative to the fjord, demonstrating how a seiche directly caused the 9-day-long seismic signal. Our findings highlight how climate change is causing cascading, hazardous feedbacks between the cryosphere, hydrosphere, and lithosphere.

Science↗

USGS2019

Persistence of intense, climate-driven runoff late in Mars history

Mars is dry today, but numerous precipitation-fed paleo-rivers are found across the planet’s surface. These rivers’ existence is a challenge to models of planetary climate evolution. We report results indicating that, for a given catchment area, rivers on Mars were wider than rivers on Earth today. We use the scale (width and wavelength) of Mars paleo-rivers as a proxy for past runoff production. Using multiple methods, we infer that intense runoff production of >(3–20) kg/m 2 per day persisted until <3 billion years (Ga) ago and probably <1 Ga ago, and was globally distributed. Therefore, the intense runoff production inferred from the results of the Mars Science Laboratory rover was not a short-lived or local anomaly. Rather, precipitation-fed runoff production was globally distributed, was intense, and persisted intermittently over >1 Ga. Our improved history of Mars’ river runoff places new constraints on the unknown mechanism that caused wet climates on Mars.

Science Advances↗