Spectacular 'calving' sets ice crashing off glacier

The ice calving at the Tasman Glacier. Photo / Denis Callesen

Up to 50 million tonnes of ice has come crashing down off the South Island's Tasman Glacier in a dramatic show of nature that has created a series of new icebergs.

The ice "calving" off the glacier's terminal face has left at least 20 significant icebergs, measuring at least 50m by 50m above the waterline, in the Tasman Glacier Terminal Lake.

"The scale of what's happening here is just enormous," said Denis Callesen, general manager of tourism for Aoraki/Mt Cook Alpine Village.

"The biggest berg is about 300m by 200m and 40m high - and that's only the 10 per cent of the berg we can see - 90 per cent is below the waterline.

"These bergs now take on a life of their own, flipping, turning and moving as natural forces take action."

The process began this month when the terminal face rose 20 to 40m, thanks to a downpour which lifted millions of tonnes of ice from the water across the entire 600m width of the face.

On August 18, a small section of that ice calved off, resulting in one large iceberg separating from the face. Then at the weekend the rest of the uplifted ice broke away in the biggest calving in the lake's 35-year history.

Glacier Explorers, which takes passengers on cruises on the lake, will resume operations ahead of schedule next month to take advantage of the new icebergs.

"We are expecting the most spectacular season ever here, with stunning viewing of nature in action," said Mr Callesen. "Visitors ... will be in for a trip of a lifetime."