A Delaware-sized portion of Antarctica’s forth-largest ice shelf calved off, sometime between July 10th and 12th, following the rapid propagation of a 127 kilometer (79 mile) long crack running through the sheet. The resulting iceberg is over 200 meters (656 feet) thick, and covers roughly 6,000 square kilometers (Delaware itself is only 5,130 square kilometers (1,982 square miles). This will likely place it as the third-largest known iceberg in modern history.

"The rift was barely visible in these data in recent weeks, but the signature is so clear now that it must have opened considerably along its whole length," explains professor Adrian Luckman, with Project Midas at Swansea University, a research group that has been keeping a close eye on the iceberg’s development. The final split was confirmed by both NASA’s Aqua satellite and Europe’s Sentinel-1.

Thankfully, the iceberg is slow moving, due to it’s sheer mass, and isn’t contributing to sea level rise, as the ice shelf it calved off of was already in the water. There are concerns regarding the potential breakup of the remaining 90 percent of the Larsen-C ice sheet, as it is what is keeping the land-bound glacier behind it from sliding rapidly into the sea.

The two largest confirmed icebergs were Iceberg B-15 (11,000 km²), calving from Antarctica’s Ross Ice Shelf in 2000, and Iceberg A-38 (6,900 km²), originating from the Filchner-Ronne Ice Shelf in 1998.