The earth's surface is made up of two types of crust:

• Oceanic crust - found underneath the oceans. It is denser than continental crust and can be subducted.
• Continental crust - found under land masses or continents. It is generally older than oceanic crust and is less often destroyed.

Earthquakes are found along all types of plate margins as shown on this map. Volcanoes however, only occur at constructive and destructive plate margins.

Hawaii is an arc of volcanic islands, found above a hot spot.