Largest Piedmont Glacier in North America

Caitlin Dempsey

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A piedmont glacier is a valley glacier which has spilled out onto relatively flat plains, spreading into bulb-like lobes.  The formation of a piedmont glacier happens when ice flows down a steep valley and spills out onto a relatively flat plain.

Alaska’s Largest Glacier

The largest piedmont glacier in North America, and outside the polar regions, is in found in southeastern Alaska and is known as the Malaspina Glacier.  Malaspina Glacier is also Alaska’s largest glacier and lies west of Yakutat Bay.

The glacier is named after Alessandro Malaspina, an Italian explorer with the Spanish Navy who visited the area in 1791.  Malaspina Glacier was designated as a National Natural Landscape in 1968.

This piedmont glacier is 65 km (40 mi) wide and 45 km (28 mi) long, with an area of some 3,900 km(1,500 sq mi).


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Aerial view of a piedmont glacier in Alaska.
The Malaspina Glacier is located in Wrangell-St. Elias National Park, Alaska. Photo: National Park Service, public domain.

Compound Glacier

Malaspina Glacier is a compound glacier, formed by the merger of several valley glaciers. The Malaspina is divided into three lobes. The western lobe of the Malaspina is formed by the Agassiz glacier, the center lobe by the Seward glacier, and the eastern lobe by the Marvine glacier.

This perspective view of Malaspina Glacier was created from Landsat satellite imagery and topography from Shuttle Radar Topography Mission (SRTM).  This color composite shows glacial ice in light blue, snow in white, vegetation in green, bare rock in grays and tans, and the ocean (foreground) in dark blue. Agassiz Glacier is on the left and Seward Glacier is on the right with Malaspina Glacier in the middle.

Titled visualization based on satellite data of the Malaspina Glacier.
Malaspina Glacier. Source: NASA.

In this Landsat image, the brown lines are due to moraines. Moraines are areas where soil, rock, and other debris have been scraped up by the glacier and deposited at its sides.

The moraines’ curves and zig-zag pattern are created when the glacier “surges.” Glaciers in this region of Alaska “surge” on a periodic basis, lurching forward rapidly for one to several years. As a result of this uneven flow, the moraines along the borders and between glaciers can get folded, crushed, and sheared, resulting in the Malaspina’s unique loops.

The different lobes of the Malaspina Glacier are labeled in this image.

Satellite image of a piedmont glacier in Alaska with the different lobes labeled.
Malaspina Glacier. Image acquired September 24, 2014. Source: NASA.

References

AGU research spotlight: Student’s research provides insight into world’s largest Piedmont glacier. (2021, December 14). Geophysical Institute. https://www.gi.alaska.edu/news/agu-research-spotlight-students-research-provides-insight-worlds-largest-piedmont-glacier

Hansen, K. (2015, October 11). Malaspina glacier, Alaska. NASA Earth Observatory. https://earthobservatory.nasa.gov/images/86767/malaspina-glacier-alaska

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About the author
Caitlin Dempsey
Caitlin Dempsey is the editor of Geography Realm and holds a master's degree in Geography from UCLA as well as a Master of Library and Information Science (MLIS) from SJSU.