1. G148: Volcanoes and Earthquakes

2. What is a volcano?
an opening in the Earth’s surface through which lava (molten rock), gas, and/or ash is released from the Earth’s interior.
a mountain that is built up from solidified lava and/or ash

3. What is an earthquake?
a sudden movement of the Earth’s surface along a fracture known as a fault.
most earthquakes result from the sudden release stored energy resulting from stress.

4. Why study volcanoes and earthquakes?
They’re both natural hazards with the potential to kill a lot of people.
They give us information about the interior of the Earth, and tell us about plate tectonics.
They have other effects: climate change, exploring for natural resources, etc.

5. Image credits
Title page: Mt. St. Helens erupting on July 22, Photo from USGS.
Title page: Damage from Nisqually Quake in Olympia, February 28, Photo from USGS at
What is a volcano: Fissure eruption on January 5, 1983 on Kilauea’s east rift zone. Photo from Hawaii Volcano Observatory at
What is an earthquake: Offset due to Landers, California earthquake, June 28, Photo from Southern California Earthquake Data Center at
Why study volcanoes and earthquakes: Cascadia subduction zone image from USGS at