Earth Science

Earth as a Planet

Seismic Waves

Study Tip
Waves are simply types of periodic motion. Perhaps you have seen the same terminology used in functions for math class or physics class.

Waves

Energy is transmitted in waves. The high point of a wave is called the crest and the low point is called the trough. The distance between waves from crest to crest, or trough to trough, is called the wavelength. The height from the centerline to the crest is called the amplitude.

Study Tip
Waves are simply types of periodic motion. Perhaps you have seen the same terminology used in functions for math class or physics class.
Study Tip
The same way a person may cast a shadow over another person when they stand under the sun, planets or celestial bodies that have aligned themselves cast shadows over one another as well.

Body Waves

The study of seismic waves is called seismology. There are two main types of seismic (earthquake) waves that tell us about the Earth’s interior. Body waves move through the solid body of the Earth, and there are two types of these waves.

P-waves (primary waves) are the fastest and move in a compression/expansion motion, producing a change in volume in Earth materials as they’re squeezed and let go. They slow down as they approach the outer core.

S-waves (secondary waves) arrive behind P-waves and travel at about half the speed. They move in an up/down perpendicular motion and only travel through solids. Body waves cause jolts during earthquakes.

Body waves
Waves

Surface Waves

Surface waves travel on the Earth’s surface and are the slowest seismic waves. The rolling motion of these waves causes the most damage during earthquakes.

Concept Check
  • What are the main parts of a wave?
  • What is seismology?
  • Describe body waves and surface waves.
  • Differentiate between P-waves vs. S-waves.