The magma then rises to the earth's surface, and a volcano is born. The edges of two plates may also move apart, leaving a space. When this happens, magma may move up into the space, and again, a volcano erupts. In some cases, two plates may slide past one another. A place where this happens is called a fault.
Most faults are under the earth's surface, but there is one that can be clearly seen.
It is in the United States in California. It is called the San Andreas fault. Here, the edges of two plates are sliding past one another, and the deep ridge between them can be seen. It looks like a long crack or scar on the earth's surface. Earthquakes often happen along faults.