Posted on 04/15/2003 10:09:31 AM PDT by blam
Glacier crack places Peruvian city in peril
15:46 15 April 03
NewScientist.com news service
The city of Huaraz lies at the end of several valleys headed by glacial lakes (Image: NASA/GSFC/METI/ERSDAC/JAROS and ASTER Science Team)
A glacial flood is threatening to sweep away a Peruvian city, satellite imagery has revealed.
An ominous crack has been spotted in a large glacier high in the Peruvian Andes. The glacier feeds into Lake Palcacocha, which is at the head of a valley leading down to the city of Huaraz.
NASA scientists are warning that if a large glacier chunk breaks off and falls into the lake, it will flood the Rio Santa Valley and devastate Huaraz in less than 15 minutes. The city, with a population of 60,000, is 270 kilometres north of the capital Lima.
The crack was detected by an Earth-monitoring instrument called ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) aboard NASA's TERRA satellite on 8 April.
"Aster's unique vantage point from space gives scientists another tool with which to see early signs of potential glacial flood-burst events and to monitor changes in glacial behaviour over time," says Michael Abrams, associate ASTER team leader at NASA's Jet Propulsion Laboratory in California.
Abrams says the Peruvian authorities will incorporate the ASTER data with information from ground-based monitoring and would then take the necessary steps to minimise the risk to people and property.
"There certainly have been large falls of ice and rock in these Peruvian glaciers which, especially if associated with lakes, tend to cause a lot of devastation," said David Vaughan, a glaciologist with British Antarctic Survey in Cambridge, UK. "ASTER is a very good way of monitoring."
Recurring nightmare
Ice from the glacier has already fallen into the lake in 2003, cutting off the water supply to Huaraz for eight days in March, according to John Reynolds, an expert on the country's glaciers.
His company, Reynolds Geo-Sciences, is working with the authorities in Peru. They are dealing with the problem, he says, but they have limited resources and need international help. "This problem is not unique to Peru either," Reynolds told New Scientist. "It's an ongoing manifestation of climate change."
The Rio Santa Valley has suffered glacial floods since at least 1702. A particularly terrible event struck in 1941, killing as many as 7000 people in Huaraz.
"You can't stop the ice avalanche, so the only way really to mitigate it is to take water out of the lake," says Reynolds. This is done by using siphons, open water channels or tunnels.
Vaughan notes that towns often spring up near glacial outwash streams, as these provide a source of clean water in all seasons from either rainwater or glacial melt. "The upshot is that the towns are pretty much in the path of outwash flood events," he says.
Shaoni Bhattacharya
Image From Science Daily
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