Volcano debris avalanche deposits in China

Chinese scientists have found the first evidence of volcanic debris avalanche deposits in China, similar to those found after the 1980 eruption of Mount St. Helens in the United States.

Deposits in the debris avalanche zone. Picture courtesy: Google

Professor Liu Xiang with Jilin University found that dozens of hummocks near Wudalianchi Lake in Northeastern Heilongjiang province are debris avalanche deposits from two volcanic eruptions that occurred in 1720 and 1721.

Liu's article on the discovery was published in the latest issue of Geological Review, a journal sponsored by China Geological Society.

Liu points out in the article that Mount Laohei and Mount Huoshao at the lake side are volcanos that took shape 160,000 years ago. Their eruptions in the 1770s were accompanied with strong avalanches, which produced the hummocks.

The largest distance of hummocks from the eruptions is as far as 2 km. The hummocks are composed of grey purple basaltic volcanic agglomerate and volcanic breccia, which is the same as that of the rocks on the two mountains, Liu said.

He said that globally, scientists have discovered evidence of more than 20 volcanic avalanche events since 1500, but it is the first of such evidence found in China.

Liu said hazards from the avalanches as well as that from the ensuing pyroclastic flow and lahar could cause damage 50 to 60 km away from the volcano. Early precautions should be taken to reduce casualties.

Scientists believe the volcanic study near Wudalianchi Lake is significant in reducing hazards linked to volcano eruption disasters and discovering environmental changes as well as exploring mineral resources.

Wudalianchi, also known as 'Five Volcanic Lakes,' is seated at an altitude of 596.9 metres above the sea level. It was formed when volcanic magma erupted over three million years ago. - Xinhua