Earthquakes are measured on the Richter scale, a thin layer of broken and crushed rocks between two blocks of rock in the earth's crust is known as a fault. When a there is a sudden slip in the faults or when two faults hit, an earthquake is formed.
Volcanoes are measured by mapping, once mapped they can keep track of how fast flows are and GPS devices receive the radio waves from global positioning system satellites to determine the position of the receiver on the Earth's surface. Portable receivers record positions to within 15 feet, which is well suited for lava-flow maps. Volcanoes can also make very beautiful structures (as shown below) the lava cools and leaves amazing different forms in the rock. volcanoes can also cause climate change once the exploed. realsing all the ash in the air can cause the sun to be blocked and the adverage tem to drop the following year, the lava and ash can also desrtoy the plant life effecting the animals and humans living in that area. 
earthquakes are destuctive in the fact that they kill hundreds of thousands of people when they happen, they take everything away from evetyone when they hit. they test are ability to come together and help one another, when we really need it, so they kind of both good and bad. Earthquakes could be a new start for people who really need it.
http://www.youtube.com/watch?v=bgRnVhbfIKQ&feature=player_embedded (watch this:)
earthquakes are destuctive in the fact that they kill hundreds of thousands of people when they happen, they take everything away from evetyone when they hit. they test are ability to come together and help one another, when we really need it, so they kind of both good and bad. Earthquakes could be a new start for people who really need it. 
http://www.youtube.com/watch?v=bgRnVhbfIKQ&feature=player_embedded (watch this:)
http://library.thinkquest.org/03oct/01424/how_are_volcanoes_measured.htm
