However, pressure and stress builds up until the friction is overcome. The size of an earthquake is relative to potential energy build up before the friction is overcome. When the energy is released wave energy is created. These seismic waves then travel through the ground creating earthquake movement and shaking. Volcanoes are cone shaped hills on the Earth's surface composed of lava flows, tephra and volcanic ash.
Most volcanoes occur at the plate subduction zones and mid-oceanic ridges.
The Hawaiian Islands were created this way. Geologists have classified five types of volcanoes. Intrusive igneous features form when hot magma from the asthenosphere migrates up into the continental crust. To be intrusive this migration must stop before it reaches the Earth's surface. If it reaches the Earth's surface we then have a volcano.