THE CHANGING PLANET

YOU'RE THE GEOLOGIST! Let's test your talent as a geologist. Can you answer this question? You have learned how nature wears away the Earth's crust by weathering and erosion. If that was the only thing that happened to the surface of the Earth, what would the crust look like after millions of years? Write down your hypothesis and then highlight the box below to find the answer. The Earth's crust would eventually become flat. All the mountains and hills would be weathered and eroded away.
How did you do? The Earth has been around for about 4.6 billion years or so. Since there are still mountains and hills on the planet, there must be something causing the Earth's crust to build mountains again. Here is another geology question for you. What in the world can make mountains? Do you know the answer? Give it your best shot and then check the box below to find out how you did. Forces deep within the Earth's crust push up the crust. These forces sometimes cause some spectacular and disastrous events on the Earth. We call them volcanoes and earthquakes.
Although the Earth's crust may look solid, it is constantly changing. Forces within the Earth are moving the crust in different directions. The three types of forces are: Tension - Stretching or pulling forces Compression - Two or more forces pushing against each other from different directions Shearing - Twisting tearing forces These forces slowly change the surface of the Earth. Compression and shearing sometimes push up the Earth's crust. Over time what was was once a shallow sea may become a mountain top. Uplift is the term given for this process. Material that is eroded away by the forces of nature will eventually be recycled in this process.

FAULT FACTS! In order to understand more about the process of uplift, you need to know a little more about the Earth's crust. The surface of the Earth has many breaks in it. These breaks, called fractures, are often buried so that we cannot see them. Sometimes the Earth's crust moves along these fractures. When this happens, we call them faults. Although they cannot always be seen, faults play a very important part in shaping and reshaping the Earth's surface. Can you see the fault line in the photo to the left?

TWIST BEND AND SHOUT "The mountains seemed to walk" is what a Chinese writer said about an earthquake he experienced. During earthquakes whole sections of land can be moved out of place. Earthquakes begin as pressures build in and under the crust. As the pressure increases, the crust begins to bend. Just like a stretching a rubber band, rocks may stretch and/or twist until they eventually break and cause the ground to shake. And when earthquakes occur, movement may occur in a number of different ways. One part of the crust can be pushed up or down, or sometimes both sides move in opposite directions. Movement along the faults may also be horizontal. Sometimes the rock layers of the crust are squeezed together until they form a series of hills and valleys. If enough pressure is applied, the rock layers may be pushed over until they lie on their sides. Over many thousands and even millions of years, this process forms mountains.

Mt. Everest, is the planet's highest mountain at 8,848 meters (28,314 feet)

 

YOU'RE THE RESEARCHER There are many mountains in Utah formed by a variety of geologic processes. Find out more about a particular mountain or a mountain range in Utah. Answer the following questions: How was the mountain formed? Is it near a fault system? How old is the mountain? From what material is the mountain made? What is the elevation of the mountain? How was the mountain named? Take pictures of the mountain or use the Internet to download some photographs of the mountain you selected. Use the research that you gathered and your computer to make a presentation. Share the presentation with your classmates.

 

YOU'RE THE SCIENTIST! Forces in the Earth's crust can push layers of rock up, down, or sideways in and on the Earth's crust. This process forms many of the mountains and valleys on this planet. You can make models of these processes with plasticene clay. NOTE: Salt dough is too sticky and does not work well for this activity. You can get more ideas for the activity below by clicking on the arrows.
Can you explain what forces the arrows above represent?	MATERIALS: This is what you will need. Several colors of plasticene clay Talcum powder Plastic tray or waxed paper Any other materials that you might think of that can demonstrate compression, tension and/or shearing forces. You may want to experiment with with elastic and brittle objects
PROCEDURE: This is what you will do. Place a layer of one color of plasticene clay on the tray. Sprinkle talcum powder on top of this layer so it does not stick to the next layer. Put another layer of a different color of plasticene in the box, and sprinkle talcum powder on top of it. Continue this until you have a layer for every color of plasticene you have. Use this model to represent the rock layers of the Earth. Use this model to demonstrate compression, tension and shearing forces. Pull both ends apart, push both ends together, or twist the ends in opposite directions. Observe and record the pattern produced. Draw pictures or take photos of your models. Study diagrams of folding, bending, and rifting in rock formations. Try to simulate those formations. Adjust the amount and speed of the force to get different results. Explain what geologic features the above forces form on the Earth's crust.

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Revised March 1, 2002 by Kathleen Ochsenbein