Muir Glacier is a

glacier A glacier (; or ) is a persistent body of dense ice, a form of rock, that is constantly moving downhill under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires ...

in Glacier Bay National Park and Preserve in the U.S. state of

Alaska Alaska ( ) is a non-contiguous U.S. state on the northwest extremity of North America. Part of the Western United States region, it is one of the two non-contiguous U.S. states, alongside Hawaii. Alaska is also considered to be the north ...

. It is currently about wide at the terminus. As recently as the mid-1980s the glacier was a tidewater glacier and calved

iceberg An iceberg is a piece of fresh water ice more than long that has broken off a glacier or an ice shelf and is floating freely in open water. Smaller chunks of floating glacially derived ice are called "growlers" or "bergy bits". Much of an i ...

s from a wall of ice 90 m (200 feet) tall. The glacier is named after Scottish-born naturalist

John Muir John Muir ( ; April 21, 1838December 24, 1914), also known as "John of the Mountains" and "Father of the national park, National Parks", was a Scottish-born American naturalist, author, environmental philosopher, botanist, zoologist, glaciologi ...

, who traveled around the area and wrote about it, generating interest in the local environment and in its preservation. His first two visits were in 1879 (at age 41) and 1880. During the visits, he sent an account of his visits in installments to the '' San Francisco Bulletin''. Later, he collected and edited these installments in a book, ''Travels in Alaska'', published in 1915, the year after he died.

Retreat

Muir Glacier has undergone very rapid, well-documented retreat since its

Little Ice Age The Little Ice Age (LIA) was a period of regional cooling, particularly pronounced in the North Atlantic region. It was not a true ice age of global extent. The term was introduced into scientific literature by François E. Matthes in 1939. Mat ...

maximum position at the mouth of Glacier Bay around 1780. In 1794, the explorer Captain George Vancouver found that most of Glacier Bay was covered by an enormous ice sheet, some in places. In 1904 the glacier reportedly "broke through the mountains" with Pyramid Peak to the west and Mt. Wright and Mount Case to the east. From 1892 to approximately 1980, it had retreated nearly . Between 1941 and 2004, the glacier retreated more than and thinned by over . Ocean water has filled the valley replacing the ice and creating Muir Inlet. The 1941 image shows the Muir Glacier as a tidewater glacier, prominently up to 700m thick, with its terminus visible on the lower right corner of the photo, well connected to its tributary, the Riggs Glacier, visible in the upper right part of the photo. By 1950, the Muir Glacier had retreated by more than 3 km and had thinned by more than 100m but remained connected to the Riggs Glacier. By 2004, the Muir Glacier had retreated further inland, and its terminus was no longer visible in the photograph. The Riggs Glacier had also undergone significant changes, retreating by 0.25 km and becoming disconnected from the Muir Glacier.

Vegetation Vegetation is an assemblage of plants and the ground cover they provide. It is a general term, without specific reference to particular Taxon, taxa, life forms, structure, Spatial ecology, spatial extent, or any other specific Botany, botanic ...

began to dominate the landscape where ice once prevailed.

References

Glaciers of Glacier Bay National Park and Preserve Glaciers of Hoonah–Angoon Census Area, Alaska Glaciers of Unorganized Borough, Alaska {{Alaska-glacier-stub

Retreat

See also

References