John Sonntag / NASA
A 2,239 square mile iceberg (roughly the size of Delaware) has broken off of Antarctica's Larsen C ice shelf. The chunk of ice weighs over a trillion tons.
Climate scientists have been monitoring the rift ever since the Larsen A ice shelf disintegrated in 1995. The Larsen B ice shelf also collapsed in 2002 following a similar calving event in 1995. It's possible that Larsen C will regrow and stay stable, but it's also possible it will meet the same fate as the other ice shelves.
Why it matters: Ice shelves are floating on water already, so they don't contribute to sea level rise. However, they act as sort of dams, keeping land-based glaciers from flowing into the sea. Such glacial flows could gradually contribute to sea level rise. Regardless of what happens, the geography of the Antarctic peninsula is forever changed.
When it happened: The iceberg calved sometime between Monday and Wednesday. The event was detected by NASA's Aqua MODIS satellite, and was reported by the MIDAS project out of Swansea University this morning.
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