Scientists have been waiting for the PIG to calve since October 2011 when they first noticed a spectacular crack spreading across its surface. Confirmation that the fissure had extended the full width of the glacier was obtained on Monday.
It was seen by the German TerraSAR-X satellite. This carries a radar instrument that can detect the surface of the ice stream even though the Antarctic is currently in the grip of winter darkness.
The berg that broke away was part of the PIG's ice shelf - the front segment of the glacier that lifts up and floats as it pushes out into the ocean. The shelf will reach tens of km beyond the grounding line.
German researchers have been receiving images from TerraSAR-X every three days or so, hoping to understand better the processes that drive the glacier forward and prompt it to fracture.
This will help them improve the computer models that are used to forecast future changes in the Antarctic.
"We were very keen to see how the crack propagated," said Prof Angelika Humbert, a glaciologist with the Alfred Wegener Institute. "We need proper calving laws, to be able to describe the evolution of ice sheets over centuries," she told BBC News.
Very big tabular bergs will come off the end of the ice shelf every 6-10 years. Previous notable events occurred in 2007 and 2001....
A 2011 NASA image of the Pine Island Glacier
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