A Magnitude 6.5 Shook an Uninhabited Arctic Island and Knocked a Mountainside Onto a Glacier. Thawed Permafrost Was the Reason It Let Go.

Permafrost is frozen ground, and in steep terrain the ice does a specific mechanical job: it fills the fractures in the rock and holds the slope together the way cement holds concrete. When it thaws, the rock is still there, but nothing is gripping it.

On March 10, 2025, a magnitude 6.5 earthquake struck Jan Mayen, a small volcanic island in the far northern Atlantic that belongs to Norway and is uninhabited except for the crew of a weather station. It sits about 500 kilometers (310 miles) east of Greenland and 550 kilometers (340 miles) north of Iceland, thrown up by the same Mid-Atlantic Ridge volcanism that built Iceland. Within minutes of the main shock, a slope above the Kjerulf Glacier collapsed. Volcanic rock and permafrost debris poured down and spread across the ice, leaving mounds known as molards and covering the glacier nearly to the shoreline, roughly 7 kilometers (4 miles) from the epicenter. Satellite data also caught the neighboring Weyprecht Glacier calving from the shaking.

An international team has now published its reconstruction of the event in the Proceedings of the National Academy of Sciences, and its central question was not why an earthquake happened — Jan Mayen shakes often — but why this one tore the mountain down.

"This 2025 earthquake is a striking example of cascading natural hazards," said lead author Guilherme W. S. de Melo, a postdoctoral researcher in the Marine Geodynamics unit at the GEOMAR Helmholtz Center for Ocean Research Kiel. "Our study documents, for the first time, an earthquake-triggered rock avalanche on Jan Mayen island. The volcanic slope may have become increasingly unstable due to permafrost degradation."

To pin the sequence down, the researchers combined local and regional seismic records, ground-shaking models, high-resolution satellite imagery, air temperature and climate records, and infrasound — low-frequency sound below human hearing — which let them time the slope failure precisely against the shaking that caused it.

The comparison that makes the case is historical. The island is home to Beerenberg, the world's northernmost active volcano, which last erupted in the 1980s and sends glaciers roughly 2,000 meters (6,600 feet) from its crater rim down to the sea. Earthquakes here are routine. Yet 40 years of satellite observations show no earthquake-triggered rock avalanche on Jan Mayen with a debris field remotely comparable to this one.

The team reads that as evidence of a slow change in the rock itself rather than anything unusual about the quake. As the Arctic warms, the ice inside fractures that stabilized these steep volcanic slopes for thousands of years is losing its binding effect. The shaking has not gotten worse. The mountain has gotten weaker — which means the same earthquakes that a warming Arctic has always had are now capable of doing things they did not used to do.