Seismic Evidence

Objectives:
1. Describe how the movement of seismic waves through the Earth contributes to knowlege of the state of matter, size and density of Earth's interior.
2. Explain why waves refract as they cross density boundaries.
3. Explain how seismic evidence shows the location of the moho, aesthenosphere, cores.

30. that the reasons we need to understand the structure and processes deep inside the Earth are that those stuctures and processes affect the surface by causing earthquakes, raising the crust of the planet, widening oceans, causing volcanos, and producing materials which may be valuable as resources.

2. that earthquakes are a shaking of the surface of the Earth caused by a sudden movement along a fault.

3. that P waves are the vibrations from earthquakes that produce a forward and back (push-pull) motion of molecules along the direction of travel of the wave.

3.1 that P-waves travel faster than other seismic waves, so they arrive at sesmographs first, and so are refererred to as primary waves.

3.2 how the motion of molecules of a P-wave allows it to travel through liquids.

4. that S waves are the vibrations from earthquakes that produce a side to side (shearing) motion of molecules perpendicular to the direction of travel of the wave.

4.1 that S-waves travel slower than P-waves, so they arrive at sesmographs second, and so are refererred to as seconary waves.

4.2 how the motion of molecules of a S-wave prevent it from travelling through liquids.

30. that p and s wave vibrations from earthquakes are recorded by seismographs.

31. that evidence about the interior of the Earth is indirect, because the deepest mines, drilling, have only penetrated about 12 km (7 mi), and the Earth is 6370 km (3900 mi) to the center.

32. that seismic waves provide most of the evidence about Earth's interior similarly to the way ultrasound provides a picture of the inside of the human human body.

33. that P-waves will travel through solids and liquids, s-waves only go through solids.