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Largest glacier in Yosemite stops moving

February 8, 2013

The Lyell Glacier, seen here at the far right of the range of mountains, lies at the headwaters of one fork of the Tuolumne River and has now stopped moving. The glacier is the largest glacier in Yosemite National Park and the second biggest-glacier in the Sierra. Photo/Wendilyn Grasseschi

 

The Lyell Glacier, the largest glacier in Yosemite National Park, has stagnated, or ceased its downhill movement, according to a recent study conducted by scientists from the National Park Service and the University of Colorado.

The adjacent Maclure Glacier is still moving at its historical rate, about one inch a day.

 Glaciers are defined as long-lasting ice masses that arise from the accumulation of snow, and move downhill by flowing and sliding, according to the park.

“A glacier’s health is determined by the amount of winter snowfall compared to summertime melting of snow and ice,” according to a National Park Service news release. “The movement of a glacier is primarily determined by the glacier’s thickness and steepness. Because they are sensitive to environmental conditions, glaciers are important indicators of climate change.

“Building on historical research conducted by John Muir and other notable individuals in Yosemite’s history, the research team monitored the Lyell Glacier and the Maclure Glacier, deep in Yosemite’s high-country. Data collected from the stakes placed on the Lyell Glacier showed that no movement has occurred within the last several years. Earlier research on the glacier showed that it was moving in the 1930s.

“Stagnation has therefore occurred since that time, perhaps within the past decade. In addition, the Lyell Glacier has decreased in size by about 60 percent since 1900, and has thinned by approximately 120 vertical feet. This thinning of the glacier is most likely why the glacier has stopped moving.

“The Lyell Glacier has historically been recognized as the largest glacier in Yosemite National Park and the second largest in the Sierra Nevada,” said Yosemite National Park Geologist Greg Stock, who co-led the investigation with Robert Anderson of the University of Colorado.

“However, the lack of movement suggests that the term ‘glacier’ no longer accurately describes this feature.”

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