NASA Earth Observation: Pine Island Glacier

This combination of Dec. 10, 2013, left, and March 11, 2014 photos provided by NASA Earth Observation, shows a large iceberg separating from the Pine Island Glacier and traveling across Pine Island Bay in Antarctica. 

Scientists are watching the iceberg, which is bigger than the island of Guam, as it slowly moves away from the glacier, bottom right in December, upper left center in March. 

NASA Earth Observation scientist Kelly Brunt said it is more a wonder than a worry and is not a threat to shipping or sea level rise. 

AP Photo /NASA Earth Observation

Brunt said the iceberg, named B-31, is about 255 square miles (660 million sq. kilometers), roughly six times as big as Manhattan and as much as 1,600 feet (487 meters) thick.

It broke off from the critical Pine Island Glacier last fall and researchers have been watching it move away ever since.

She said it is completely natural for icebergs to split off from glaciers in Antarctica, however this calving does shrink the Pine Island Glacier beyond its 30-year normal.