A glacier protruding from Antarctica's Mt Erebus, the site of New Zealand's worst ever aviation disaster, has calved.

Antarctica New Zealand spokeswoman Lisa-Marie Brooks said a 3km chunk of the Erebus Glacier Tongue had broken off and was bobbing in McMurdo Sound.

It had formed a huge flat-top iceberg which was floating away from the glacier with the current.

Each kilometre of the iceberg would contain about 5 million tonnes of ice, Ms Brooks said.


"To put that into perspective, if 5km had calved it would have contained enough water to supply Auckland for the next 150 years.''

She said it was a natural event which occurred relatively regularly.

In 1911, a 4km piece of the glacier broke off in a gale. It calved again in the 1940s and in 1990.

According to Nasa's Earth Observatory website, the Erebus glacier comes down from Mt Erebus and protrudes off the coast of Ross Island, forming an 11-12km ice tongue - a long, narrow sheet of ice projecting out from the coastline.

On November 28, 1979, Air New Zealand flight 901 crashed into Mt Erebus, instantly killing all 257 people on board.