When people think of tsunamis, they usually picture giant waves caused by undersea earthquakes. That image is accurate, but the story is larger. Earthquakes and glaciers are often connected, and in certain parts of the world, the retreat of glaciers can play an unexpected role in generating destructive waves.
A tsunami begins when the seafloor shifts suddenly, displacing water. The most common cause is a powerful earthquake along a subduction zone, where one tectonic plate slips beneath another. Alaska, Japan, and Chile are familiar examples. These massive jolts can push up or drop sections of the ocean floor, setting in motion waves that race across entire ocean basins.
But glaciers also enter the picture. In regions such as Alaska, Greenland, and parts of the Himalayas, glaciers sit close to tectonically active zones. Earthquakes can destabilize glacial valleys, triggering landslides of ice and rock into fjords. The sudden collapse of a glacier tongue or a massive calving event can displace water in the same way an earthquake does, creating a tsunami that may devastate nearby communities. In fact, some of the tallest tsunami waves ever recorded did not come from undersea earthquakes but from landslides linked to glacial valleys.
One dramatic example occurred in 1958 in Lituya Bay, Alaska, when a magnitude 7.8 earthquake shook loose about 30 million cubic meters of rock into a fjord bordered by retreating glaciers. The impact sent a wave more than 500 meters high surging across the bay, stripping trees and reshaping the landscape. While rare, such events highlight how glaciers can magnify earthquake impacts.
Climate change adds another layer to this story. As glaciers retreat and thin, they leave behind steep, unstable slopes. Earthquakes in these regions become more likely to trigger landslides, which in turn can produce localized tsunamis. In Greenland, where large glaciers end in fjords, scientists have recorded smaller tsunami waves created by collapsing ice chunks. These events serve as warnings of what might happen if larger volumes of ice were to fail during a seismic event.
Understanding the links between earthquakes, glaciers, and tsunamis is critical for hazard planning. Remote communities in Alaska or the Arctic may face overlapping risks: strong shaking from tectonic faults and sudden waves from destabilized glacier valleys. Monitoring systems that track both seismic activity and glacial changes are becoming essential tools for early warning.
Tsunamis remind us that Earth’s systems are interconnected. Quakes deep below the crust and ice high in the mountains may seem worlds apart, but together they can unleash forces powerful enough to reshape coastlines and challenge human resilience. In a warming world, the icy role in tsunami hazards will likely grow more important.