The most powerful geologic force on the planet -- glaciers, can dominate an entire continent, reshape a continent's surface features in the blink of a geologic eye. Places glaciers among the Earth's geological forces. Presents distribution and makeup of glaciers today and past Ice Ages and describes how glaciers grow and shrink. Shows how glaciers are the most important geologic factor in climate change. Includes interviews with leading glacier experts from around the country. Spanish subtitles. .