I understand they’re big ol’ chunks of ice, but are they one solid mass? What is defined as the “border” of a glacier? I’ve seen discussions of the dangers of underground glacial rivers, what’s the deal with those?
In: Planetary Science
A glacier is a place in the mountains where more snow falls during winter than melts during summer. The snow then builds up year after year.
As the weight of the new snow presses down on the old snow, the old snow gets compacted into very dense, solid ice. When the pressure rises more and the ice on top of the mountain presses down on the ice further below, the whole glacier starts moving and “flowing” very slowly even though it is all solid.
As the ice flows down the mountain over the course of many years, at some point it reaches an altitude where more ice melts than new ice is pushed down from the mountain top. This is where the glacier ends.
Glaciers are mostly solid ice, but there are cracks and holes in the ice. These can either form from mechanical stress, when the glacier moves. Or water from melting ice can basically “cut” them into the glacier. They are really dangerous because you can fall into them and they are often not visible on the surface when they are covered by a thin layer of ice and snow.
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