Drumlins cover the surface of the tilted planation surface as it dips beneath the Atlantic (Unit 911). Many of the drumlins are composed of "red" tills (Unit 434) carried by glaciers at least 100 km from the north. Erosion of drumlin islands and headlands has formed many shoals, some beaches, and tidal marshes in Mahone Bay (District 460). Exposed slate headlands with scattered drumlins have a harsher climate, resulting in coastal forest habitat (Unit 832).