Week of Dec. 8

The above image is a seismometer

The above wave image is seismogram - the image below shows seismic waves

The image below is the seismogram data of the 2011  - 9.0 earthquake in Japan (The seismic data shows the earthquake as an 8.9 - it was upgraded to a 9.0)

Earthquake Simulator Interactive

How Do We Know About the Layers of the Earth? 

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

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!

                        

Links:

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

Observe Earthquake Wave Movements - Animation

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