Practical Geology

Investigate glaciers, which now cover about 10% of Earth’s land area; 25,000 years ago, they covered 30%. Learn how to spot evidence of past glaciation—from sculpted valleys in Yosemite National Park, to the cliffs at Vicksburg, Mississippi (which formed far from glaciers), to Minnesota’s 10,000 lakes. Dig into the physics of glaciers: how they develop and the forces they exert.