Why this massive Alaskan ice lobe is technically not a single glacier at all

Countries & Cities · Published 30 September 2026 Swipe more like this →

In short: Spanning thousands of square kilometers in southeastern Alaska, the Malaspina Glacier is the world's largest piedmont glacier. Yet, geologically speaking, it is a phantom. It is actually a compound merger of several distinct valley glaciers that spill onto the coastal plain, creating a spectacular, crinkled landscape of ice and moraine.

The Malaspina Glacier serves as the classic example of a piedmont glacier, a formation occurring when valley glaciers exit a mountain range and spread out onto lowlands, no longer confined by steep walls. In this case, the system is formed by the convergence of the Agassiz, Seward, and Marvine/Hayden glaciers as they descend from the Saint Elias Mountains. Because these components are officially classified as independent entities, the Malaspina does not technically exist as a singular geological unit, though it is widely recognized as a massive, unified lobe.

The glacier's surface is marked by spectacular, contorted moraines—elongated piles of rock and debris—created as the ice is pushed from behind by faster-moving valley glaciers. Beneath this surface, the ice reaches thicknesses of up to 600 meters, with parts of its base estimated to sit 300 meters below sea level. Despite its proximity to the Gulf of Alaska, the ice does not reach the ocean, meaning it is not classified as a tidewater glacier.

As a sensitive indicator of climatic change, the Malaspina provides critical data for researchers. Satellite imaging, including Landsat and the Shuttle Radar Topography Mission (SRTM), has allowed scientists to map its extent since 1972. Evidence suggests that between 1980 and 2000, the system lost approximately 20 meters of thickness. Given its immense scale, this shrinkage alone contributed about 0.5% to the rise in global sea levels during that period, highlighting the glacier's significant role in planetary climate dynamics.

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