Iceberg four times the size of London breaks off from Antarctica ice shelf

The massive berg, calved from the Larsen C Ice Shelf, is about 5,800 square kilometres in size and weighs about a trillion tonnes. It is believed to have separated from the main ice shelf after a Nasa satellite, which takes thermal images, appeared to show a crack that has been forming for some time had finally broken through.

However the berg has not yet floated away from its position, which could be because it's grounded on underwater hills or because of sea currents and winds. Writing on the Project Midas website, which covers Antarctic research, scientists said: "A one trillion tonne iceberg – one of the biggest ever recorded – has calved away from the Larsen C Ice Shelf in Antarctica. "The calving occurred sometime between Monday 10 July and Wednesday 12 July 2017, when a 5,800-square-kilometre section of Larsen C finally broke away. The iceberg, which is likely to be named A68, weighs more than a trillion tonnes. Its volume is twice that of Lake Erie, one of the Great Lakes."

While the iceberg is huge, it is about half the size of the largest one ever recorded, which was 11,000 square kilometres. It broke off the Ross Ice Shelf in 2000 and passed by New Zealand about six years later. A line showing the original ice edge was drawn on the purple thermal image taken by Nasa, which shows the crack extending in a loop from one stretch of coast to another.

The scientists said the iceberg itself would not have an effect on global sea levels as it was already floating on the water. However it may end up having a considerable impact as its removal could speed up the flow of glaciers from the land into the sea.

"The calving of this iceberg leaves the Larsen C Ice Shelf reduced in area by more than 12 per cent, and the landscape of the Antarctic Peninsula changed forever," the scientists said.

"Although the remaining ice shelf will continue naturally to regrow, Swansea researchers have previously shown that the new configuration is potentially less stable than it was prior to the rift.