1. Earth’s Changing Structures
SSA Review 5 –
Earth’s Changing Structures

2. Earthquakes What is an Earthquake?
Earthquake – the shaking of the Earth’s crust caused by a sudden movement of the Earth’s tectonic plates.

3. Seismic waves – the vibrations through the Earth caused by the earthquake
Carries the energy away from the focus, in all directions through the Earth’s interior, and across the surface.

4. Tectonic stresses causing Earthquakes
Tension – the crust is stretched

5. Tectonic stresses causing Earthquakes
Shearing – the crust is pushed and pulled in opposite directions

6. Tectonic stresses causing Earthquakes
Compression – the crust is squeezed

7. Most volcanoes form along convergent boundaries (subduction zones)
Volcano – an opening on the Earth’s crust where magma erupts onto the surface.
Most volcanoes form along convergent boundaries (subduction zones)

8. Types of Eruptions
1. Quiet eruption – the lava flows gently down the side of a volcano

9. Types of Volcanic Eruptions
2. Explosive – lava explodes out of the volcano
*Pyroclastic flow – eruption that sends out ash, volcanic rocks, and gases
Mayon Volcano - Phillipines