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.

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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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