Planet Earth: An Illustrated History

Meltwater
Glaciers around the world are melting at a precipitous rate. In some cases, the meltwater can form into flowing streams, like this one in Greenland. The water can also penetrate cracks that run deep within the ice, eventually making its way to the ground, where it acts as a lubricant, causing glaciers to slide more quickly toward the sea.

• The Book, "TIME Planet Earth: An Illustrated History"