These glaciers can vary greatly in size, from a football-field sized patch to a river a hundred miles long. You can imagine how a billion-ton icecube can rearrange the landscape as it slowly grinds its way overland. Many lakes, such as the Great Lakes, and valleys have been carved out by ancient glaciers. The ice on Greenland approaches two miles in thickness in some places and is so heavy that some of the land has been compressed so much that it is way below sea level. Here's a map of where glaciers and icecaps exist in the world.
White areas show glaciers and ice sheets around the world.
The white spots in the oceans are islands where glaciers are found. At that time, glaciers covered almost one-third of the land. About three million years ago the seas could have been up to 165 feet higher.