Satellite image of iceberg B17B in Ross Sea. (NASA/HO)

SYDNEY, Australia -- A monster iceberg twice the size of Manhattan is drifting towards Australia, raising fears that a collision with the continental shelf could cause tremors in the country.

The iceberg – known as B17B - measures 140 square kilometres. It broke off Antarctica's Ross Ice Shelf in 2000 along with several other icebergs. Only B17B, however, has travelled this far north, now drifting about 1,700 kms from Australia's west coast.

"B17B is a very significant one in that it has drifted so far north while still largely intact. It's one of the biggest sighted at those latitudes,” reported Neal Young, the glaciologist who spotted the glacier, writing on the Australian Antarctic Division.

An iceberg this large has not been reported in waters this far north in more than 100 years.

It has stayed completely still in one spot for about five years, but is now on the move again, raising some concern that it could crash into the continental shelf, causing medium-sized tremors in Australia.

However, Dr. Young said the iceberg was unlikely to come anywhere near the mainland in its present, gigantic form, as the warmer waters are already causing it to melt.

"As the water warms up the iceberg is slowly breaking up, resulting in hundreds more smaller icebergs in the area," he said.