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The solid crust that we stand on seems very strong and stable. The plates we live on are constantly in motion. Normally we don't feel this motion, but every once in a while the earth reminds us how dynamic it actually is.

An earthquake is the vibrations we feel when the Earth's crust suddenly moves. What causes these sudden, larger movements of the crust? You have probably played with a rubber band, even shooting it at your brother or sister. When you stretch the rubber band, you know that it will normally snap back. If you pull it too far, it will break. The earth's crust act much in the same way. The plates can stretch so far, but if they stretch farther than their elastic limit, they will break and release huge vibrations that can be felt large distances away.

The crust moves along cracks called faults. A fault is a break in the earth's crust. The earth can move in different directions depending on the type of fault. The more energy that is released, the stronger the earthquake. Strong earthquakes cause major damage. The USGS provides data on earthquakes that have happened in the past week. The earthquake locations have their longitude and latitude data given. Use a map and plot these earthquakes to see where they are happening. What kind of a trend do you see happening?

 

Another method for energy to escape from inside the Earth is through volcanoes.

A volcano is formed when magma reaches Earth’s surface before it has a chance to cool. When a volcano explodes, thinner lava can flow down the sides like a river. Sometimes the lava is really thick and it is ejected as chunks.

Some volcanic eruptions are quiet. Some volcanic eruptions are quiet. The lava oozes down the side of the volcano like Mt. Kilauea in Hawaii, or the Parcutin volcano pictured here. (All photos courtesy of the USGS)

Hawaii Volcanoes National Park
April 1986, Pu'u O'o Eruption, Kilauea Volcano, Hawaii

 
Others are explosive like Mt. St Helens. mountsthelensexplodingimage
 
The Smithsonian Institution provides a weekly report about the volcanic activity throughout the world. This data also includes the latitude and longitude for each volcano. Add these locations to your map - which already has the earthquakes on it.
 
Visit Pioneer Library and search e-Media for the video "Geologists Notebook: Why land goes up and down?"
 

Analysis:

  1. What kind of relationship do you observe when you see current volcanoes and earthquakes plotted together?
  2. Are there more volcanoes, or earthquakes, that happen in the same week?
  3. From the data you saw, which were more disruptive this week, earthquakes or volcanoes?

Review Science safetey rules here.

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Updated October 24, 2008 by: Glen Westbroek

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