Field notes: the changing coast

A class is investigating a rocky coastline in Australia. They find a dark, fine-grained rock near an old volcanic vent, layers of shell fragments and sand in a nearby cliff, and shiny, folded rock deeper inland. Over time, waves break rock into smaller pieces. Rivers carry sediment to the sea, where it settles in layers. Buried layers are compacted and cemented. In some places, existing rock is changed deep underground by heat and pressure without melting. Magma can cool underground or as lava at the surface. Uplift can expose buried rocks, while weathering and erosion break them down again.