When glaciers melted after the Great Ice Age, they reshaped some parts of the landscape into mounds called drumlins.
Drumlins can be several hundred yards (meters) long, and their length runs in the direction the ice was moving. A drumlin field may contain hundreds of these earthen mounds.
Similarly, eskers point in the direction the ice flowed, but they are longer and twist and turn like a raised earthen snake or stream. Tunnels of water carrying loads of sediment and debris formed under glaciers.
When the glaciers melted, the rocks and silt were left as eskers, long winding streams of earth.