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Crust in Motion Chapter 5, Section 1 Monday, January 25, 2010 Pages 144-153.

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Presentation on theme: "Crust in Motion Chapter 5, Section 1 Monday, January 25, 2010 Pages 144-153."— Presentation transcript:

1 Crust in Motion Chapter 5, Section 1 Monday, January 25, 2010 Pages 144-153

2 Objectives Understand how stress forces affect rock. Describe why faults form and learn where they occur. Learn how movement along faults change Earth’s surface.

3 Vocabulary Words Earthquake Stress Deformation Shearing Tension Compression Fault Strike-slip fault Normal fault Hanging wall Footwall Reverse fault Fault-block mountain Fold Anticline Syncline Plateau

4 What is an Earthquake? An earthquake is the shaking and trembling that results from the movement of rock beneath Earth’s surface.

5 Earthquake -- cont’d Powerful forces cause the Earth’s plates to squeeze rocks together and pull it in different directions. This type of force is called stress. Stress adds energy to rocks.  When this stored up energy changes the shape of rocks or breaks the crust, it is called deformation.

6 Types of Stress Causing Deformation There are three kinds of stress that cause deformation:  Shearing: pushes a mass of rock in two opposite directions.  Tension: pulls on the crust and stretches the rock.  Compression: squeezes the rock until it folds or breaks. Shearing, tension, compression work over millions of years to change the shape and volume of rock.

7 Types of Faults There are three types of faults:  Strike-slip fault: rocks on either side of the fault slide past each other sideways with little up or down motion. Caused by shearing.

8 Types of Faults -- cont’d Normal fault: one block of rock lies above the fault while the other block lies below it.  The block above is called the hanging wall and the block below it is called the footwall.  Normal faults are caused by tension.

9 Types of Faults -- cont’d Reverse Faults: the hanging wall slides upward past the footwall.  Reverse faults are caused by compression.

10 Movement Along the Fault The amount of movement depends on how much friction there is between them.  Low friction means the blocks slide constantly without sticking.  High friction is when the blocks lock together.  When the amount of stress is greater than the amount of friction, the blocks will suddenly unlock and cause an earthquake.

11 Fault-Block Mountain Formed when normal faults uplift a block of rock. A fold is a bend in rock that forms when compression shortens and thickens part of the crust.  A fold that bends upward in an arch is an anticline.  A fold that bends downward in the middle to form a bowl is a syncline.  A plateau is formed when a fault pushes up a large flat block of rock. A plateau is a large area of the flat land elevated high above sea level.

12 Homework Workbook 5.1 (1/27) Vocabulary quiz 5.1 (1/27)

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