Encyclopedia Article


Glaciers are huge bodies of ice that form because they accumulate more mass (from precipitation) than they lose (from melting and evaporation) over time. Glaciers can grow and shrink annually, just as they seem to expand and then retreat over the earth's surface. Because glaciers are so massive, their sheer weight causes them to move downhill, often changing the topography of the earth's surface in the process.

Photo Credit: 

"Glacier in Paradise Valley, Mount Rainier National Park, circa 1920," photograph by Asahel Curtis. William.