Prakash Mathema / AFP / Getty Images The Khumbu Glacier, one of the longest glaciers in the world, in the Everest-Khumbu region, on Dec. 4, 2009.

Melting glaciers and rising temperatures are forming a potentially destructive combination in the deep ravines of Nepal’s Himalayan foothills, and the Phulping Bridge — on the Araniko Highway linking Kathmandu with the Chinese border — is a good place to see just how dangerous the pairing can be.

A bare concrete pillar stands there, little noticed by the drivers of trucks, laden with Chinese goods, that rattle along at high speeds across the bridge, about 110 km from Kathmandu. The pillar is all that’s left of the original Phulping Bridge, which was swept away by floodwaters in July 1981. The deluge was not caused, as is common, by monsoon rain, but by the bursting of a glacial lake. The force of the raging torrent was strong enough to dislodge boulders 30 m across. They still lie in the Bhote Koshi River.

(PHOTOS: Vanishing Glaciers)

Glacial-lake outbursts, as they’re known, are not new. They occur every time the natural dams of ice or accumulated rocky deposits that hold back glacial lakes give way because of seismic activity, erosion or simple water pressure. Millions of cubic meters of meltwater can be released as a result, sometimes over the course of a few days or — far more frighteningly — in a matter of minutes. During the past century, at least 50 glacial-lake outbursts were recorded in the Himalayas, according to data maintained by the Kathmandu-based International Centre for Integrated Mountain Development (ICIMOD). But what is new is that the lakes are forming and growing much more quickly because the glaciers are melting faster than ever.

The potential of a Himalayan tsunami is a hazard of global warming that has yet to be given much attention by outsiders, but it is a daily preoccupation of ICIMOD program coordinator Pradeep Mool. He told TIME that there were some 20,000 glacial lakes in the Hindu Kush Himalayan region, extending from Afghanistan to Burma. In some parts of the Himalayas, like the Dudh Koshi area in eastern Nepal, the melt rate is alarmingly high.

“Almost all the glaciers [in Dudh Koshi] are retreating at rates of 10 to 59 m annually,” Mool says, “but the rate for some has accelerated during the last half-decade to 74 m annually.” He explained that this had created 24 new glacial lakes in the area, which now had a total of 34 such bodies of water. At least 10 of them are considered dangerous.

Research by a team from the University of Milan, released this month, found that in the past 50 years glaciers in the Everest region had shrunk by 13% and the snow line was now seen about 180 m higher up. Sudeep Thakuri, a researcher with the team, says the melting was most likely caused by warming temperatures and was certain to continue. Since 1992, premonsoon and winter temperatures in the Everest region have increased by 0.6ºC.

Earthquakes also add to the risk. “Earthquakes could act as major triggers for glacial-lake outbursts,” Mool says. He feels that much better monitoring of the lakes is needed to get a proper assessment of the dangers.

Down in the Bhote Koshi Valley, villagers now rely on text messages for warnings of potential floods, landslides and other hazards. The power station near the village of Jhirpu Phulpingkatt will issue a warning of a glacial-lake outburst, but people in the area will only have a few minutes’ notice before the floodwaters arrive, and only glacial-lake outbursts in Nepali territory can be immediately detected. There are at least six glacial lakes close by in Tibet that lie outside the warning system, and their outbursts will be detected only when the waters enter Nepali territory, according to the plant’s acting manager Janak Raj Pant. But regardless of where an outburst originates, he says, “All of us would have to run for our lives.” Seaborne tsunamis have already unleashed enough terror this century. Let’s hope that no comparable disasters dwell in the Himalayas’ icy ravines.

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