These images from NASA’s Earth Observatory show Greenland’s Petermann Glacier calving an iceberg — watch the lower right quadrant of the image to see the split go from a hairline crack to a visible break. The resulting iceberg is twice as big as Manhattan.

In 2010, Petermann calved an ice island that was twice as big as this one. But this year’s berg is notable as well: It split off further upstream than usual, which may indicate that warmer water is circulating under the glacier and weakening the ice.

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