Week of Dec. 8
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| The above image is a seismometer |
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The above wave image is seismogram - the image below shows seismic waves  |
Evidence!
1. Earthquakes give off seismic waves that travel through the Earth
- The speed and direction of the P and S waves change based on what type of material they pass through
- P waves travel through BOTH solids and liquids, S waves only travel through solids - this tells us that the Earth's interior is both solid and liquid
- Both P waves and S waves speed up in colder materials and slow down in hotter materials - this tells us that the Earth's layers have different temperatures
- Seismic waves slow down in hotter, less dense material and speed up in colder, more dense material
2. Our Magnetic Field
- Since we have a magnetic field, the Inner Core has to be solid metal surrounded by liquid metal - Outer Core - and they have to be spinning in order to create the field
3. Meteorites
- Some rocky meteorites have the same composition of the Earth's crust and mantle
4. Mantle Rock
- Sometimes rock from the mantle are blasted out of a volcano - they show differences in density and composition compared to rocks from the crust
Let's Take A Look At Earthquakes!
1. How Do Earthquakes Happen?
Anatomy of an Earthquake
2. Where do Earthquakes Happen?
- Notice the relationship between plate boundaries, volcano locations, and major earthquake locations!
- Most earthquakes occur at plate boundaries; the movements of the plates create breaks in the Earth's crust called faults.
- There are 3 types of faults that occur at the 3 specific plate boundaries:
Transform - Strike-Slip Fault - Shear Stress
Divergent - normal fault - tension stress
Divergent - normal fault - tension stress
Convergent - reverse fault - compression stress
Ground Movements Faults
3. How Do We Find Out Where an Earthquake Happened?
Locating the epicenter:
1. P and S waves travel at different speeds to at least 3 seismograph stations
2. The difference in their arrival times is called lag time - lag time can be extrapolated and then used to locate the epicenter of the earthquake through a process called triangulation
3. The radii of the circles is the distance from the epicenter to the city
4. The point where all 3 circles meet is the epicenter of the earthquake!
Seismic Waves - Video Clip
Observe Earthquake Waves Moving Through Earth's Interior - Animation
How Do We Know About the Layers of the Earth? Digital
Lesson
How Are Earthquakes Related to Plate Tectonics? Digital Interactive
Earthquake Simulator Interactive
Where Was That Earthquake? Digital Activity
Live Earthquake Map - Realtime
Japan's Earthquake Tsunami Explained (2 min) Video
Japan's Earthquake (45 min) Video
