Iceberg Almost The Size Of Greater London Breaks Off In Antarctica Iceberg Almost The Size Of Greater London Breaks Off In Antarctica The research body said the iceberg measuring 1,270 square kilometres (490 square miles) had broken off from the 150-metre-thick Brunt Ice Shelf in a process called "calving". This came almost a decade after scientists first saw massive cracks had formed in the shelf. London, United Kingdom: A vast iceberg almost the size of Greater London has broken away from the Antarctic ice shelf near a British research station, the British Antarctic Survey said Friday. The research body said the iceberg measuring 1,270 square kilometres (490 square miles) had broken off from the 150-metre-thick Brunt Ice Shelf in a process called "calving".