Gauteng and NW Province

5-mile-long landslide in Alaska national park; warming eyed as possible culprit

By Miguel Llanos, msnbc.com

A massive landslide sent tons of rock and debris tumbling more than five miles down a glacier in Alaska, the National Park Service reported in an event that could be yet another sign of a warming world.

Located in a remote area of Glacier Bay National Park, the slide was so big it registered on earthquake monitors as a magnitude 3.4 event.

Officials noticed the monitor blip on June 11 but it wasn’t until July 2 that a pilot passing over the site took photos that showed just how large it was.

“It’s certainly the largest that we’re aware of” inside the park, Glacier Bay ecologist Lewis Sharman told msnbc.com.
Larger landslides have happened over geologic time, Marten Geertsema, a natural hazards researcher for the Forest Service in nearby British Columbia, told msnbc.com, but it definitely was “one of the longest runout landslides on a glacier in Alaska and Canada in recent times.”

Moreover, the force was enormous, Geertsema said. No one was present, but had anyone been there they probably “would be blown over by the air blast,” he told the Associated Press.

Officials ruled out an earthquake as the trigger that caused part of the nearly 12,000-foot Lituya Mountain to give way, smothering the ice-white Johns Hopkins Glacier with dark rock and debris over an area a half-mile wide and 5.5 miles long.

One possibility is that thawing permafrost, which is ground that stays frozen for two or more years, caused the slide.

“We are seeing an increase in rock slides in mountain areas throughout the world because of permafrost degradation,” said Geertsema.

“I don’t know whether permafrost degradation played a role here, but we can be almost certain that permafrost exists on Lituya Mountain,” said Geertsema,”Certainly this type of event could happen from permafrost degradation.”

Many areas of mountain permafrost have been thawing in recent decades as temperatures warm, and some experts are becoming convinced that thawing is a factor in the frequency of rock slides, Geertsema said, pointing to data by Swiss scientists studying the Alps.

“It plays an important role,” Geertsema said of climate change. “I think we have been underestimating the role it might play.”

Sharman, the park ecologist, echoed that sentiment, saying he’s heard from experts that “they would not be surprised” to see more such landslides inside the national park if temperatures continue to warm.

“The landslide is approximately 12-14 miles up the glacier,” the park said, and the glacier itself moves material towards the bay only about 10-15 feet a day. “So this debris may not reach the face of the glacier for many years,” it added.

The frozen ground that covers the top of the world has been thawing rapidly over the last three decades. But there is cause for concern beyond the far north, because the carbon released from thawing permafrost could raise global temperatures even higher.

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