Ice melting in the frozen peat created these shallow ponds and lakes in the Hudson Bay Lowlands in Manitoba, Canada. The lakes are up to several hundred meters across. (High-resolution image not available)
—Credit: Geological Survey of Canada

The idea of frozen ground might seem simple. But how it forms, why it is important, and where scientists find it are difficult questions. Plus, frozen ground is sometimes hidden under plants, snow, and even oceans.

In this section, Physical Science, find out how frozen ground forms, and how it affects the landscape. Learn how deep the ground can freeze. Find out how to tell the difference between seasonally frozen ground and permafrost.