Eskers were formed by streams that ran through glaciers and deposited sand and rubble in their beds. After the glacier melted, the esker remained as a long, narrow ridge similar to a rail bed on the landscape.
Here a stream has worked a channel through a glacier, leaving a column standing next to the rest of the original wall. The back wall is carved out at its base by the running water. The walls and column show layers created by years of snow deposition. This is all visible because the flow of water is low now.