2 Match the words in the box with the sentences. There are two extra words.
cave cliff dune falls lake
ocean volcano wave
1 An area of water surrounded by land.
2 A dangerous mountain..
3 A sandy hill in the desert or on the beach.
4 A high rock face, often on the edge of the sea.
5 Moving water on the sea.
6 A hole in the side of a hill or underground.