Mount Everest climbers blocked by massive 10-story-high ice chunk

A massive, unstable chunk of ice, roughly the size of a 10-story building, is blocking the Nepali access route of Mount Everest, stranding hundreds of climbers who are left unsure of when they’ll attempt their ascent.

The towering ice block, called a serac, is in the Khumbu Icefall above South Base Camp and nearly 1,000 feet below Camp One. It was officially declared unsafe April 24.

Seasoned Sherpa climbers known as Icefall Doctors prepare the path for Everest climbers each spring. They discovered the serac April 10 and determined it could collapse onto the route.

That means safety specialists will have to find an alternate route, or wait for the serac to melt enough to collapse on its own. It could fall soon – or it could take some time, Reuters said.

Meanwhile, would-be climbers continue to arrive at Base Camp. At least 410 of them have been issued permits, at a price of $15,000 each, to make the ascent.

Where is ice blocking Mount Everest route?

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The Mount Everest climbing season runs from April to May, when the weather conditions are best for reaching the 29,032-foot summit. The route usually opens by the third ​week of April.

Mountain climbing is ​a major source of income ⁠and employment for Nepal, home to eight of the world’s 14 highest peaks.

"Expeditions are all being delayed because of the impasse," Garrett Madison ​of U.S.-based Madison Mountaineering told Reuters from base camp.

Among those waiting to ascend are 98 climbers, including 24 women, from China, the most from any country so far. Official data also showed 49 from the United States and 46 ⁠from India, Reuters said.

Everest straddles the border between Nepal and China’s Tibet region. It can be climbed from both sides, though most climbers approach from ​the Nepali side.

The seracs and crevasses of the Khumbu Icefall are dangerous for climbers of Mount Everest and the neighboring peaks of Lhotse and Nuptse. All three share part of the ascent route, according to ExplorersWeb.

On the mountains, fast-moving glaciers create building-size blocks of ice. As glaciers move, the ice blocks become unstable and collapse, burying mountainsides in tons of ice.

Collapses in the Khumbu Icefall have killed many climbers, including more than a dozen sherpas in 2014.

SOURCE USA TODAY Network reporting and research; Reuters; explorersweb.com; himalayan-masters.com