Drumlins are elongated, teardrop-shaped hills of rock, sand, and gravel that formed under moving glacierice. They can be up to 2 kilometers (1.25 miles) long.
This photograph of Smith Drumlin Prairie, Wisconsin, shows a ground view of the elongated hump shape of a drumlin. —Credit: Joshua Mayer
This field of drumlins was photographed while flying over Peterborough County in Ontario, Canada. Note the drumlins are all aligned in the same direction, which indicates the direction the glacier flowed. —Credit: Sean Marshall
Clew Bay (Irish Cuan Mó), Ireland, contains a field of sunken drumlins, or drumlins that are now partially underwater. —Credit: Éole Wind