An iceberg with an area almost twice the size of Atlanta has broken away from the Antarctic continent and is drifting into the ocean, which could threaten shipping lanes in the Southern Ocean during the Antarctic winter. The floating, frozen island has been named iceberg B31. Scientists have reported from NASA’s Earth Observatory that B31 spans 255 square miles and is estimated to be roughly a third of a mile thick.

Iceberg B31 calved off Antarctica’s Pine Island Glacier last November, and the crack that began the separation was first spotted by NASA in 2011. So far, B31 has drifted out of Pine Island Bay and into the Amundsen Sea, off the western side of Antarctica. In a statement from NASA, Grant Bigg from the University of Sheffield in England said, “The iceberg is now well out of Pine Island Bay and will soon join the more general flow in the Southern Ocean, which could be east or west in this region.”

NASA’s Earth Observatory posted a clip delineating the path of B31’s movement, utilizing the Moderate Resolution Imaging Spectroradiometer (MODIS)-equipped Terra and Aqua satellites:

Icebergs are free-floating, massive pieces of freshwater ice that have broken off a glacier or an ice shelf. Due to the conflicted densities between pure ice and seawater, typically only one-tenth of the volume of an iceberg is above water. This had fostered the expression “tip of the iceberg,” and contributed to the sinking of the RMS Titanic in 1912.

Robert Marsh, a scientist at the University of Southampton in England, said an iceberg of B31’s magnitude can take a year to melt. The largest iceberg ever recorded was iceberg B15, which was the size of the state of Connecticut, at 4,250 square miles. B15 calved off Antarctica’s Ross Ice Shelf in March, 2000. Fragments of B15 still float around the Antarctic today.

Iceberg b31 covers 255 sq. miles and is on the move. It's also been shortlisted to host World Cup 2026 if it doesn't melt first.

— Doug Bartow (@dougbartow) April 22, 2014

Image via NASA