Figure 29 The lithosphere is broken into about a dozen large plates, which move slowly over Earth's surface.

Interpreting Maps What type of boundary exists between the Pacific plate and the Cocos plate?

d

Plates move away from each other along a divergent boundary, shown in Figure 30. The mid-ocean ridge forms a divergent boundary. Divergent boundaries can also be found on land, for instance, in Africa. When plates move apart, magma rises from the mantle to fill the gap. The magma cools to form new rock at the edge of each plate.

Plates come together, or collide, at a convergent boundary. The most common convergent boundary is one where an oceanic plate is subducted beneath a trench. When oceanic crust collides with continental crust, the denser oceanic crust slides under the less dense continental crust. At a transform boundary, plates slide past each other, moving in opposite directions. Rock is neither created nor destroyed at a transform boundary.

Figure 30 Plates meet at three types of boundaries: divergent boundaries, convergent boundaries, and transform boundaries.

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