August 22, 2008—Greenland's glaciers are breaking up at a worrisome pace, new satellite images show.

A gigantic, 11-square-mile (29-square-kilometer) chunk of the Petermann Glacier in northern Greenland broke off between July 10 and July 24.

The collapsed section is comparable in size to half of Manhattan Island (see the breakup in three images above).

Petermann covers 500 square miles (1,295 square kilometers). (See a Greenland map.)

The broken chunk has led scientists to predict a section of Petermann, the Northern Hemisphere's longest-floating glacier, will disappear by 2009.

(See a photo of an ice shelf collapse in Antarctica.)

But the most alarming sign, according to Jason Box of the Byrd Polar Research Center at Ohio State University, is a huge 7-mile (11.3 kilometer) crack, seen above in the center right of the July 25 image, that has appeared farther back on the margin of the glacier.

The groove could create an imminent and even bigger breakup—up to a third of the ice field, he said in a statement.

"The pictures speak for themselves," Box told the Associated Press. "This crack is moving, and moving closer and closer to the front. It's just a matter of time till a much larger piece is going to break off … "