View of what used to be the bottom of a glacial lake in the Magallanes region, 2000 km south of Santiago, Chile, on June 4, 2007. Until two months ago visitors could admire a one-kilometre-square lake. Scientists conjecture that an earthquake could had opened a fissure in the rocks, allowing the water to drain through.

Credit: AFP/Corporación Nacional Forestal

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SANTIAGO: Geologists are trying to solve the mysterious disappearance of a large lake in southern Chile, after recently discovering a thirty-meter deep crater instead of the body of water.

The National Forests Corp. of Chile (CONAF) has asked geologists to investigate what may have caused the unnamed lake to dry up after CONAF officials were stunned to find the empty hole during a routine visit on May 27.

Cracks were found inside the hole while ice floes that once floated over water just stood at the bottom of the empty lake at the Bernardo O'Higgins National Park 2,000 km (1,240 miles) south of Santiago, officials said.

"They were very surprised to see that the lake had disappeared," CONAF regional director Juan Jose Romero told Radio Cooperativa. "We're not talking about a small lake. It was quite large."

"Disappeared overnight"

"The ice floes were there, but standing at the dry bottom of the lake, which disappeared almost overnight," he added.

Geologists and other experts were tasked with determining the cause of the lake's disappearance, which also led to a dramatic drop in the water level of a river it fed.

As a possible explanation for the disappearance, geologists said ice flows damming up the lake's natural outlet could have given way under the pressure of accumulating lake water.

"It's a frequent event in Patagonia, only it's very seldom witnessed due to the low population density of the region," said Andres Rivera, glacier expert with the Scientific Research Centre of Valdivia, in southern Chile.

Patagonia is a vast region shared by Argentina and Chile comprising the Andes Mountains to the west and south and plateaus and low plains to the east.

"It's a local phenomenon and not at all unusual," said Rivera. "It takes place in a very dynamic area, where these lakes form and eventually drain through the mechanics of ice."

"It shouldn't call our attention so much," he added.

"Sudden, violent torrent"

University of Chile geologist Carlos Palacios said the missing lake likely emptied after water pressure broke through a "curtain or wall" of ice and rocks at the basin's outlet.

"The problem is the resistance of the ice within the wall against the pressure of the water trapped in the basin. If the curtain ice is weakened through a melting process, the pressure finally wins out and the curtain breaks apart," Palacios said. "The outcome is a sudden, violent torrent ... and the consequential rapid drainage and disappearance of the lake."

Other hypothesis about the disappearance included an earthquake-caused crack in the ground that could have drained all the lake water. Two months ago, a strong earthquake shook the Aysen Fjord, a few hundred kilometers from the lake.

Palacios, however, was doubtful: "These phenomena, in general, are not triggered by earthquakes ... although it may have accelerated a process that probably would have happened sooner or later."