New-Zealand earthquake: collapsing giant glaciers

Scientists say the earthquake struck Christchurch - New Zealand's second-largest city seems to have brought "the last push", causing a collapse of the giant glacier in the country.

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National Geographic magazine reported that the strong, 6.3-magnitude seismic strike broke a 20-fold-sized ice sheet of a football field, vertically away from New Zealand's longest glacier. The giant ice sheet in front of the Tasman glacier collapsed into the Tasman Lake after an earthquake 200km away occurred on February 22.

Tourists witness a huge cracked ice separating from the Tasman glacier
and collapsed into the lake on February 22.(Photo: NZPA)

According to scientists, when collapsed, giant ice sheets formed waves of up to 3.5 meters in Tasman Lake.

" We heard a loud crack like a rifle bullet ," said an American tourist who took part in the glacial tour at that time in the New Zealand Herald .

Martin Truffer, a glacier expert at the Institute of Geophysics, University of Alaska (USA), said that such an event is rare but not precedent. The ice sheets of the Hubbard glacier in Alaska also broke in 1958, following a major earthquake in the southeastern state.

However, such events are not entirely random. " There must be an earthquake in the area where there is a glacier ready to crack a large piece of ice ." , Truffer emphasized.

In addition, glaciers like Tasman, which are located on the lake, tend to be less prone to cracking at the ends than the ocean glaciers. This makes the glaciers on the lake more likely to lose larger ice sheets than small ice sheets.

" A big block is probably ready to crack, and the earthquake just gives it the last kick ," Truffer added.

According to the New Zealand Herald, even before the Christchurch earthquake, tour guides received warning not to take visitors too close to the glacier due to heavy rain over the past few weeks. Truffer explained that the rain may have increased the water level of the lake, making large ice sheets easier to crack the glacier. Moreover, it is possible that one end of the glacier floats, not anchoring to the lake.