Glaciers!

This is called ablation.

Scientists think that there was one ice age about 600 million years ago, but they don't know much about that one.

Eventually it turns into glacier ice.

When an iceberg breaks loose from a glacier, it is called calving.

This is where icebergs form.

This ice has gradually receded to where it is now, mainly in the polar ice caps.

Pictures of the polar ice caps taken in different years look very different from each other.

Glaciers are always changing, but if a glacier is accumulating ice faster than it is losing ice, it is said to be growing.

3 Some glaciers extend out into the ocean from the land, forming a huge shelf of ice.

Scientists think that there was one ice age about 600 million years ago, but they don't know much about that one.

6 Satellite photographs give us great pictures of the glaciers, and by comparing photos taken at different times, we can see how glaciers change from year to year.

Ice that extends out into the ocean like a peninsula is called tongue ice.

These are located in valleys between high mountains, where the temperatures are cold enough to keep the glacier ice frozen.

These are located in valleys between high mountains, where the temperatures are cold enough to keep the glacier ice frozen.

6 Satellite photographs give us great pictures of the glaciers, and by comparing photos taken at different times, we can see how glaciers change from year to year.

5 Glaciers are not all in the Arctic and Antarctic regions.

Smaller valley glaciers flow into larger ones as they go down hill, just like streams flow into a bigger river.

9 At one time, ice covered 32% of the earth's surface, but today, it covers only about 10%.