In February 2010 about half of the Mertz Glacier Tongue, a piece of ice about long and wide and protruding out into the Southern Ocean, broke away from the main body of the Tongue. The separation occurred around the 12 or 13 February along two existing rift lines on opposite sides of the Tongue. The event was helped in part when the large Iceberg B-9B collided with it. Iceberg B-9B is a long by wide remnant of Iceberg B-9 which broke off the Ross Ice Shelf in 1987 and has recently ungrounded itself from Ninnis Bank to the east of the Tongue where it had been lodged for 18 years.