Glaciers and periodic ice ages are a normal part of Earth's long-term climate dynamics. Alpine glaciers are found in mountainous regions where higher elevations keep air temperatures cold enough for snow to accumulate into layers of ice. Continental glaciers are found in the polar regions: Greenland, the Canadian Arctic and in Antarctica. Though these regions are dry, polar deserts, temperatures are low enough to allow snow to accumulate over centuries and millenia into vast sheets of ice.
The Mechanics of Glaciation
What Causes an Ice Age? (AtlasPro 13:43)
How Ice Ages Happen - The Milankovitch Cycle (6:46)
How do glaciers shape the landscape? (OxfordEd 2:30)
How do glaciers move?
Continental Glaciation in North America
The Rise and Fall of the Great Lakes (NFB: 17min)
What's so Great and the Great Lakes? (TED-Ed 4:46)