# Seismic Waves Lesson for Kids

Instructor: Emily Lockhart

Emily has taught science and has a master's degree in education.

Learn about seismic waves and see the importance of measuring them. Discover the ways they come about and look at the scientists who record and study them.

## What are Seismic Waves

You can wave at a friend from across the room, or you can surf a wave in the ocean. A wave is a motion up and down or side-to-side. Waves are all around us, and we'll be discussing how the Earth can produce waves as well.

Scientists call the waves that travel through earth seismic waves. These waves are actually energy waves that result from earthquakes, explosions, or volcanoes. These waves are felt on earth's crust.

Earth's crust is the outside layer of our earth and very thin. It only makes up 1% of the total planet. This outer layer floats on a hot liquid rock called magma. The magma below flows like an ocean moving the crust above like a ship sailing on the water's waves. In the center of earth is a layer called the core.

## Causes for Seismic Waves

Any disturbance of the earth's crust will result in seismic waves. When magma escapes through cracks in the earth's crust it can violently shake the ground and seismic waves will result.

If the crust moves suddenly the result is an earthquake. A small earthquake could rattle the windows or glasses in the cupboard, a large earthquake would bring big buildings to rubble.

The earth's crust moves like Jello, jiggling after the tray has been moved. At first jiggling rapidly then settling down and becoming still.

## Types of Waves

When a disturbance occurs many waves are observed. Waves can be broken down into body waves and surface waves. Body waves move through the entire earth. An earthquake in Taiwan produced body waves that traveled through the earth and were detected in California. Surface waves move only the earth's crust and don't travel as far.

## Body Waves

There are two types of body waves. Primary (P) waves move in an up down motion, like dribbling a basketball. They are very fast. The rocks move like a rope during a game of tug-of-war. The rocks are pushed and pulled, compressed and pulled apart. After an earthquake these are the first waves to be felt, and detected very far from where the earthquake began.

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