Presentation on theme: "Earthquakes Liz LaRosa 2009"— Presentation transcript:
1 Earthquakes Liz LaRosa http://www.middleschoolscience.com 2009 for my 5th grade science class 2009
2 What is an earthquake?Used to describe both sudden slip on a fault, and the resulting ground shaking and radiated seismic energy caused by the slipCaused by volcanic or magmatic activity,Caused by other sudden stress changes in the earth.
3 Three Types of Faults Strike-Slip Thrust Normal Three types of faults Form depending on type of plate motion and complex reaction of earth’s lithospheric blocksStrike-slipNormalThrustNormal
4 What causes earthquakes? Tectonic plates move past each other causing stress. Stress causes the rock to deformPlastic deformation – does not cause earthquakesElastic deformation – rock stretches then reaches a breaking point, releasing energy.
5 Elastic Rebound – deformed rock goes back to its original shape
6 Focus –. point inside the Earth where an Focus – point inside the Earth where an earthquake begins Epicenter – point on Earth’s surface above focus
7 How Seismographs Workthe pendulum remains fixed as the ground moves beneath it
12 Surface Waves Move along the Earth’s surface Produces motion in the upper crustMotion can be up and downMotion can be aroundMotion can be back and forthTravel more slowly than S and P wavesMore destructive
13 How do scientists calculate how far a location is from the epicenter of an earthquake? Scientists calculate the difference between arrival times of the P waves and S wavesThe further away an earthquake is, the greater the time between the arrival of the P waves and the S waves