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Case of the missing lake puzzles Chilean scientists

A June 4 photo shows what used to be the bottom of a glacial lake in the Magallanes region 2,000 km south of Santiago, Chile. Until two months ago, visitors could admire the 2-hectare glacial lake in Bernardo O'Higgins National Park, but park rangers late last month found a 40m-deep crater where the lake had been. PHOTO: AFP

The melting of nearby glaciers or cracks in the ground caused by an earthquake were proposed by scientists on Thursday as possible causes for the disappearance of a 2-hectare glacial lake in southern Chile.

The disappearance of the lake in Bernardo O'Higgins National Park was discovered late last month by park rangers, who were stunned to find a 40m-deep crater where a large lake had been just two months earlier, when they last visited the area.

Officials said a clear explanation of why the lake vanished would likely not be known until experts visit the remote region in Chile's southern Andes.

Juan Jose Romero, head of Chile's National Forest Service in the region, said by telephone that it would take geologists and other experts about two or three weeks to reach the remote area 2,000km south of Santiago.

But, based on pictures from the site, experts were discussing hypotheses related to global warming and seismic activity.

Gino Casassa, a glaciologist at the Center for Scientific Studies, said the cause may have been a phenomenon known as glacial lake outburst floods.

"I am convinced that in this case, it is the result of global warming."

Gino Casassa, glaciologist at the Center for Scientific Studies

As glaciers retreat, glacial lakes form behind natural dams of ice or moraine. These relatively weak dams can be breached suddenly, causing the lake to drain. Possible causes include a sudden input of water into the lake, an earthquake or avalanches of ice or rock.

Casassa said the Chilean lake was fed by two glaciers, the Bernardo and the Tempano, "and both are receding."

The water level of the lake could have risen with the increasing flow from the melting glaciers.

"At the same time, the increased amount of water opens a tunnel under the ice, emptying the lake," Casassa said.

Another glaciologist, Andres Rivera, said that "most glaciers in the region are receding as a result of the global warming."

This may both create new lakes or cause others empty, he said.

Casassa said glaciers can recede for other reasons than global warming. It can be the result of the natural dynamic of glaciers, which recede or grow.

"But I am convinced that in this case, it is the result of global warming," he said.

The empty lake is about 1,500m above sea level.

Romero said another theory is that the water disappeared through huge cracks at the bottom of the crater. He said the cracks may have been caused by the strong quake that rocked the region on April 21.
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