A massive iceberg calved off of Antarctica’s Larsen-C ice shelf this week, as the rift between the iceberg and ice shelf grew unexpectedly quick over the last few weeks, reports Nicola Davis for The Guardian. For a number of years, scientists have tracked the progress of the rift, expecting the iceberg to be one of the largest ever. The Larsen-C calving comes seven years after it’s northerly neighbor, Larsen-B, broke from the ice shelf in 2010.

The rift in Larsen-C has grown quickly this summer, spreading as much as 10 kilometers in a day. There is considerable debate as to whether climate change caused the calving. Some scientists credit warming oceans, while others highlight the cycles that ice shelves undergo, calving naturally and then regrowing. Either way, the iceberg is afloat in the Weddell Sea and the stability of Larsen-C is in question.