Earthquakes and Earth's Layers

​After reading the article and answering questions, you should now have a better understanding about what they are. Now we are going to learn about how we use them to understand Earth better.

​Earthquakes can cause a lot of destruction and lead to different types of natural disasters, including tsunamis, landslides, and avalanches. Engineers and city planners have to take the probability of the risk factors into consideration before building.

Along with these disasters, they release seismic waves that can be tracked and used to understand the earth's interior structure.

​Seismic Waves

​Pressure waves (aka primary waves aka p-wave)
- travel through solids and liquids
- quickest traveling seismic wave
- travel longitudinally (parallel)
Shear waves (aka secondary waves aka s-waves)
- travel through solids (don't go through liquids well)
- second fastest traveling seismic wave
- travel transversely (perpendicular)

​Lag time - time between P-Wave and S-Wave arrival. The longer the time, the further away the earthquake.

​Bigger squiggles (larger waves) represent stronger earthquakes.

​Earth's Interior

Seismic waves help us understand earth's interior composition and physical properties. As they go through more dense material, they travel faster, which causes them to curve. When they reach a new layer, they change direction completely because it's a different state of matter.

We know the outer core is liquid because S-Waves can't go through it. This is recognized b the S-Wave Shadow Zone on the opposite end of the planet from where the earthquake happened.

​Compositional Layers
-Crust
-Mantle
-Core (Iron and Nickel)

Physical Layers
-Lithosphere (Rigid, Solid)
-Asthenosphere (Soft/Plastic, Solid)
-Mesosphere (Rigid, Solid)
-Outer Core (Liquid)
-Inner Core (Solid)