Presentation on theme: "Earthquakes Liz LaRosa 2009http://www.middleschoolscience.com for my 5 th grade science class 2009."— Presentation transcript:
Earthquakes Liz LaRosa http://www.middleschoolscience.com 2009http://www.middleschoolscience.com for my 5 th grade science class 2009
What is an earthquake? The slipping and breaking of rock material along a fault. Faults are “cracks” in the crust near plate boundaries that are under stress. Stress is caused by the heat within the earth trying to escape and the movement of the plates.
Three Types of Faults Strike-Slip - shearing Thrust - Compression Normal – pulling away
What causes earthquakes? Tectonic plates move past each other causing stress. Stress causes the rock to deform – Plastic deformation – does not cause earthquakes – Elastic deformation – rock stretches then reaches a breaking point, releasing energy – kind of bounces back like a rubberband.
Elastic Rebound – deformed rock goes back to its original shape http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM
Focus – point inside the Earth where an earthquake begins Epicenter – point on Earth’s surface above focus
Seismic Waves in the Earth http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM
Primary Waves (P Waves) A type of seismic wave that compresses and expands the ground The first wave to arrive at an earthquake http://daphne.meccahosting.com/~a0000e89/insideearth2.htm
Secondary Waves (S Waves) A type of seismic wave that moves the ground up and down or side to side http://daphne.meccahosting.com/~a0000e89/insideearth2.htm
Surface Waves Move along the Earth’s surface Produces motion in the upper crust – Motion can be up and down – Motion can be around – Motion can be back and forth Travel more slowly than S and P waves More destructive
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 waves The further away an earthquake is, the greater the time between the arrival of the P waves and the S waves
How are Earthquakes Measured? Mercalli Intensity Scale Click Link for Interactive Demo http://elearning.niu.edu/simulations/images/S_portfolio/Mercalli/Mercalli_Scale.swf http://elearning.niu.edu/simulations/images/S_portfolio/Mercalli/Mercalli_Scale.swf