Earthquakes 'could rupture glacial lakes' in Himalayas

Karachi, May 16, 2011 (PPI): Glacial lakes in the Himalayas could pose a major hazard to population centres if they are ruptured by earthquakes, BBC says quoting scientists. The true risk to settlements and infrastructure downstream in Hindu-Kush-Himalayas region is difficult to assess.

But the Himalayan region is dotted with glacial lakes and is in a seismically active zone. Experts say that, on the basis of past records, a large quake in the region is overdue. Many glacial lakes are said to be growing - some of them alarmingly - because of melting glaciers. Some are at risk of rupturing, which would flood areas downstream.

There have been at least 35 glacial lake outburst events in Nepal, Pakistan, Bhutan & China during the last century, United Nations Environment Programme (UNEP) says. But increased risk from quake-induced rupture of glacial lakes has been rarely discussed. "Such a disaster is very much possible, more so, when we are expecting a big earthquake in the region now," says Sushil Kumar, a geophysicist with Indian Wadia Institute of Himalayan Geology. "If acceleration is very high in epicentre of earthquake, everything will be in the air as things will not be stable. So, naturally liquids like waters in glacial lakes will burst out."

A number of these lakes are located near seismic faults. "Given the location of lakes, if the epicentre of earthquake happens to be nearby them, they will certainly explode," says Pradeep Mool, a glaciologist with International Centre for Integrated Mountain Development (ICIMOD) that works on mountain issues in the region. A recent report by World Bank and Global Facility for Disaster Reduction & Recovery said such a hazard "is a possibility that should be considered, although prediction [of earthquakes] is beyond current competence."

Officials with Nepal's National Seismological Centre (NSC) say at least half a dozen minor tremors are recorded in the Himalayas every day. "And when the tremor is [Magnitude] five or above... we record many aftershocks as well," says Dilliram Tiwari of NSC. Landslides and avalanches can make even smaller lakes dangerous, especially during earthquakes, experts say. For instance, outburst of Dig Tsho glacial lake near Mount Everest in eastern Nepal in 1985 was triggered by a large ice and rock avalanche.

Although not created by glacial melting, a lake that formed after a landslide blocked Hunza river in Pakistan last year was caused by an earthquake, scientists there say. What has happened in these lower parts of Hindu Kush Himalayas could also occur in higher areas with glacial lakes. Glaciologists say round of glacial melting leading to formation of most new glacial lakes in Himalayas began in 1950s. The last big earthquake to hit region was in 1934.

But studies have so far focused only on retreating glaciers and expanding glacial lakes. "They have not been monitored in relation to seismicity," says Professor Asif Khan, a geologist with Pakistan's Peshawar University. "It is indeed quite worrying given the scale of impending risk."