The longest and fastest flowing glacier in the Antarctic has spawned a huge iceberg eight times the size of Manhattan Island, German researchers say.

The 280-square-mile iceberg has split from the Pine Island glacier, where scientists have been observing a giant crack spreading across its surface since October 2011.

Observations by Germany's TerraSAR-X satellite Monday confirmed the fissure had extended to the full width of the glacier, breaking the giant iceberg off the glacier's ice shelf, the front segment of the glacier floating on the ocean as it moves off the Antarctic continent.

Scientists have been scrutinizing the satellite observations hoping to understand the processes that drive the glacier forward and prompt it to fracture.

"We were very keen to see how the crack propagated," Angelika Humbert, a glaciologist with the Alfred Wegener Institute, told BBC News.

"We need proper calving laws, to be able to describe the evolution of ice sheets over centuries."

Scientists have kept a close eye on the Pine Island glacier, dubbed PIG, which calves off large icebergs from its ice shelf every 6 to10 years.

"The PIG is the most rapidly shrinking glacier on the planet," David Vaughan from the British Antarctic Survey said.

"It's losing more ice than any other glacier on the planet, and it's contributing to sea level rise faster than any other glacier on the planet. That makes it worthy of study."