Edge of a Glacier

These small boulders were ripped from bedrock four hundred miles north in Canada and carried here by a great glacier that covered nearly all of North America north and east of this place. Although the ice melted thousands of years ago, these rocks, called erratics because they are out of place, remain clear evidence that the glacier once covered this ground. From here east, the course of the Little Missouri and Missouri Rivers marks the glacier’s southern edge, where it dropped these rocks.

North Dakota · United States