An 80-mile crack is spreading across the Antarctic Peninsula’s Larsen C ice shelf. And once that crack reaches the ocean, it will calve an iceberg the size of Delaware. The chunk looked like it could break off a few months ago, but it’s still clinging on by a roughly 10-mile thread. Earlier this week, scientists from the MIDAS project, which monitors Larsen C, reported a new branch on that crack.

Icebergs naturally calve from ice shelves all the time. But scientists are concerned that the