CHAPTER TWO TEST – EARTHQUAKES
Monday Dec. 19
Make Your Index Card
HOW A SEISMOGRAPH WORKS
Click on the picture below to see an animation of how a seismograph works.
What shakes, and what doesn’t?
Click on the picture below to see
HOW TO FIND THE EPICENTER of an EARTHQUAKE
THIS WEEK’S LESSON
Earthquakes are a form of wave energy that is transferred through the crust. Motion is transmitted from the point of sudden energy release, the focus, as seismic waves that travel in all directions outward. The point on the Earth’s surface directly above the focus is termed the epicenter.
SEISMIC WAVES AND THE SLINKY
P-waves or primary waves are formed by the alternating compression and expansion of the crust. They are the first to arrive at a seismograph station, and travel in a straight line. Think of the slinky we did in class! P-waves also have the ability to travel through solid, liquid, and gaseous materials.
S-waves or secondary waves are formed by the side-to-side movement of the crust. They are the second to arrive at a seismograph station, and travel more slowly. Think again of the side-to-side slinky we did in class, or look at the example below.
- S-waves have the ability to travel through solids, but stop at liquid and gaseous materials.
- What does that mean as the waves travel through the earth’s layers?
- What happens at the Outer Core?
- What does this help geologists to know about the Outer Core?
Surface waves are something like the waves in a body of water — they move the surface of the earth up and down. This generally causes the worst damage because the wave motion rocks the foundations of manmade structures. Surface waves are the slowest moving of all waves, so the most intense shaking usually comes at the end of an earthquake.