Volcanoes 1 2 Volcanoes will form where the

Volcanoes 1 2 Volcanoes will form where the Earth’s structure allows a path for magma from the asthenosphere to rise. • Subduction zones 1 • Hot spots 2

Hot Spots 1. Magma (melted mantle) builds under the lithosphere. 2. The pressure will increase as more mantle is made. 3. Eventually the magma will pierce the lithosphere and make a large volcano.

Volcanoes 1 2 Volcanoes will form where the Earth’s structure allows a path for magma from the asthenosphere to rise. • Subduction zones 1 • Hot spots 2

Volcanoes 2 1 1. Subducting plate melts to make magma. Increased pressure in asthenosphere. 2. Some magma is forced up through the lithosphere to make a volcano.

Earthquake Mechanism Earthquakes will occur along all boundaries. Earthquakes are felt as vibrations in the Earth. The tectonic plates are always moving but the movement is not always smooth. • Sources of friction include o one plate moving over another o two parallel plates rubbing together • Tectonic forces will eventually overcome these forces • The plate “springs” back into position

Distribution of Earthquakes

1 2 – This location is the source of the earthquake – Found on the surface directly above the focus 2 1

Seismic Waves We can learn about the structure of the Earth by watching the way that seismic waves travel under the surface.