# Transferring Energy

On the previous Sci-ber text page, you learned that earthquakes and volcanoes transfer energy from inside the Earth to the surface. Now, we need to consider how this energy is transferred from the interior of the Earth, to the surface. Earth's interior has a great amount of heat energy.

# Volcanoes

 During a volcano, the heat energy is transferred through lava to the Earth's surface. The magma may come up to the surface as maglavama bringing heat energy with it. The volcanoes which erupt on the island of Hawaii are an example of this transfer of heat energy. Notice, the lava is very hot as it comes up to the surface. The lava immediately begins to cool. As the heat escapes, the lava hardens to dark black rock. Magma which becomes trapped below the surface can build up pressure that must be released as mechanical energy. An example of this release of mechanical energy was the eruption of Mt. Saint Helens in Washington State. As the heat energy in the magma built up below the surface of the mountain, the pressure increased. This pressure was released in a gigantic explosion which blew off the top of the mountain.

## Earthquakes

The transfer of earthquake energy happens in the form of waves. These waves can happen in a couple of different ways. You can demonstrate the transfer of energy through waves.

Materials:

• Two people

Safety concerns: As with all science lab activities, the most important safety rule is to follow all teacher directions.

Procedure:

1. Hold the Slinkey® as level as possible.
• Have one person gently shake the Slinkey® up and down.
• Observe how the energy moves from the person doing the shaking to the other person who is holding onto the Slinkey®.
2. Now hold the Slinkey® level on the floor.
• One person swings the Slinkey® gently from side to side.
• Observe how the energy moves from the person swinging the Slinkey® to the person who is just holding the Slinkey®.
3. Again, hold the Slinkey® level on the floor.
• While holding onto the very end of the Slinkey®, let go of the Slinkey® rings.
• Observe how the energy moves from the person pulling and letting go of ten Slinkey® rings to the person who is just holding the Slinkey®.

The energy from an earthquake arrives in three distinct waves. The fastest and therefore the first to arrive was named the Primary wave or p-wave. The second to arrive was named the secondary wave or s-wave. The slowest and last to arrive was named the surface wave.

• P-wave: P-waves are a form of longitudinal waves. These waves vibrate in a direction parallel to the direction in which the energy is transferred. For example, in an east moving p-wave objects vibrate in an east-west direction. This is the type of wave demonstrated in the first two videos above.
• S-wave: S-waves are a form of transverse waves. These waves vibrate in a direction perpendicular to the direction in which the energy is transferred. For example, in an east moving s-wave, objects vibrate in a north-south direction. This is more destructive than the vibrations in a p-wave. This is the type of wave demonstrated in the third video above.
• Surface Wave: Also known as a Love wave, the surface wave is much slower than the p-wave or s-wave. A surface wave is a combination of a transverse and a longitudinal wave in which the particles vibrate both perpendicularly and parallel to the direction of energy transfer. An object struck by a surface wave would vibrate both north-south and east-west. The result is that the objects move in a circle. This is the most destructive of the three types of wave. A surface wave is similar to the ripples you see when an object is dropped into a body of water. Observe a QuickTime video of this type of wave. (click the back button of your browser to return to this page.) In this next video, notice the motion of the ball floating in the water. If you watch closely, you can see the circular motion. Observe a QuickTime video of this circular motion. (click the back button of your browser to return to this page.)

The magnitude of an earthquake is measured on a scale called the Richter Scale. This scale was developed in 1935, by Charles Richter. The table below shows the effects of earthquakes based on their magnitude on the Richter scale.
 Magnitute Effects Less than 2 Not felt. 2-3 Usually not felt, but recordable. 3-4 Often felt but rarely causes damage. 4-5 Noticeable shaking, minor damage. 5-6 Major damage to poorly constructed objects. 6-7 Major damage over an entire city. 7-8 Serious damage over an even wider area. 8-9 Serious damage 100 miles from epicenter. More than 9 Serious damage for 1,000 miles.

Analysis:

1. In what ways is the transfer of energy similar for volcanoes and earthquakes?
2. How would you describe the three types of earthquake waves?
3. Which type of earthquake wave seems to have the greatest ability to cause problems on Earth's surface?

Review Science safetey rules here.

Get the plug-ins: , and . (The QuickTime plug-in is needed to play sounds and movies correctly.)

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