Glaciers are flowing masses of ice, created by years of snowfall and cold local temperatures. Thousands of years ago, large parts of the world were covered with glaciers. Today glaciers exist all over the world. Greenland and Antarctica are covered by thick sheets of glacier ice. There are smaller glaciers in the Rocky Mountains of North America, in the European Alps, in the Andes of South America, and even at mountainous points along the equator.
Glacier ice today stores about three fourths of all the freshwater in the world.
Continental glaciers begin with a decrease in temperature and an accumulation of snow, over tens of thousands of years.