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? Used to describe both sudden slip on a fault, and the resulting ground shaking and radiated seismic energy caused by the slip Caused by volcanic or magmatic activity, Caused by other sudden stress changes in the earth.
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.
Focus – point inside the Earth where an earthquake begins Epicenter – point on Earth’s surface above focus
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 Seismometers work 1. Detects and records the ground motion 2. A large mass is suspended from a wire. It does not move during an earthquake. (all because of inertia) 3. A pen attached to the mass marks a roll of moving paper.
How Seismographs Work http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM the pendulum remains fixed as the ground moves beneath it
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
Locating Earthquakes- Triangulating the Epicenter http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM
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