A block of ice roughly the size of Delaware is set to detach from an ice shelf in Antarctica, creating one of the 10 largest icebergs ever recorded. The incident could provoke the breakup of the entire ice shelf, which scientists predict might increase global sea levels as much as four inches.

Ice shelf Larsen C, one of the largest and most unstable, currently holds the 2,000-square-mile Western Antarctic sheet. While the break-off itself wouldn’t raise sea levels since icebergs float, ice shelves slow the flow of glaciers, which contribute to global sea-level rise.

Recent images revealed to scientists at the British Antarctic Survey that a rift in Larsen C — already more than 70 miles long and 300 feet wide — increased at a nearly unprecedented pace. If Larsen C breaks apart, scientists are concerned glacial flow would cause a 10-centimeter, or 3.9-inch rise in global sea levels.

“The calving of this large iceberg could be the first step of the collapse of Larsen C ice shelf, which would result in the disintegration of a huge area of ice into a number of icebergs and smaller fragments,” Professor David Vaughan, director of science at the British Antarctic Survey, told Science Daily.

The British Antarctic Survey researchers have known that the Larsen C shelf was volatile since August, when Project Midas, a U.K.-based research team reported the rift had grown by 13 miles after their last measurement, in March. And the current growth continues to outpace projections based on that August measurement. In December, the rift grew another 11 miles and now hangs onto the main shelf by a little over 12 miles.

Climate change is thought to be the culprit of the rift, but scientists have insufficient evidence to support the claim, according to BBC News. Aside from increasing sea levels, scientists predict Larsen C’s disintegration could have unforeseen geographical implications on the whole Antarctic Peninsula as well.