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© NASA/REUTERSThe B-31 Iceberg as it separated from a rift in Antarctica's Pine Island Glacier
Scientists are monitoring one of the largest icebergs in existence, after it broke off from an Antarctic glacier and began to head into the open ocean.

The iceberg covers about 255 square miles, making it roughly six times the size of Manhattan - and is up to 500 meters thick.

Known as B31, glacial crack that created the iceberg was first detected in 2011 but the iceberg separated from Antarctica's Pine Island Glacier in November.

NASA glaciologist Kelly Brunt said that the iceberg is not currently presenting a danger, but needs to be continually monitored.

"It's one that's large enough that it warrants monitoring. There is not a lot of shipping traffic down there. We're not particularly concerned about shipping lanes. We know where all the big ones are."

She added that scientists are especially interested because it originated in an unexpected location.

"It's like a large sheet cake floating through the Southern Ocean."

Scientists say the iceberg has floated across Pine Island Bay, a basin of the Amundsen Sea, and will likely be swept up soon in the swift currents of the Southern Ocean.