Why are there ocean basins, continents, and mountains?

Part of Hall of Planet Earth.

Exhibition hall with rock samples and explanation screens. The "Why are there ocean basins, continents, and mountains?" section of the Gottesman Hall of Planet Earth
AMNH / R. Mickens

Over millions of years, ocean basins open and close, continents move and change shape, and mountains are pushed up and eroded away. Such dynamic processes continually reshape the surface of the Earth. The movement of rigid plates on the Earth’s surface, known as plate tectonics, is the cause of these changes. Volcanic eruptions and earthquakes are dramatic hints of the great movements that take place over the vastness of geological time.

In This Section

Exhibit Wallace Gilroy Bronze Earth model The globe before you is a model of the solid Earth. Exhibit Explosive volcanism Most explosive eruptions occur in volcanoes above subduction zones, where one tectonic plate dives beneath the other. Exhibit Non-explosive volcanism People associate volcanoes with spectacular explosive eruptions. Most volcanoes erupt basalt, a fluid lava from the mantle. Exhibit Earthquakes No other natural force compares in sheer power with earthquakes. Exhibit Mountain building The mountain ranges that span the globe mark boundaries where the Earth’s plates converge. Exhibit Plate tectonics Plate tectonics has emerged as one of the grand unifying theories of geology.