2. Introducing Earth

3. Chapter Ten: Inside Earth 10.1 Sensing the Interior of the Earth 10.2 Earth’s Interior 10.3 Earth’s Surface

4. Investigation 10A What is a good way to model Earth? All Cracked up

5. 10.1 Ideas from the past The distance from Earth’s surface to its center is about 6,400 kilometers. Scientists began to study special vibrations that travel through earth. These vibrations, called seismic waves, revealed the structure of Earth’s interior.

6. 10.1 Wave Motion Seismic waves are formed from disturbances such as earthquakes and human-made blasts.

7. 10.1 Wave motion You are probably familiar with the up- and down motion of water waves in a pool. We can demonstrate side-to-side wave motion by wiggling a rope.

8. 10.1 Wave motion P-waves travel faster than S-waves and move with a forward-and-backward motion. They would arrive at a seismic station first. S-waves travel with a side-to- side motion, are slower than P-waves, and cannot travel through liquid.

9. 10.1 Wave Motion Seismic waves may be bent, reflected, or stopped as they encounter different materials as they pass through Earth. This gives scientists knowledge about Earth’s interior. When an earthquake on one side of the earth produces S-waves there is a large area on the other side of the earth called the S-wave shadow zone where the S-waves cannot be detected.

10. 10.1 Wave motion By studying what happens to the waves on their path through Earth, scientists are able to make detailed maps of Earth’s interior… 1.When S-waves are produced on one side of Earth due to an earthquake, there is a large area on the other side where the waves can’t be detected. 2.Scientists know that secondary waves do not pass through liquids. 3.With this fact and these observations, they realized that the outer core of Earth must be liquid.