Chapter 4 Lesson 1 Forces in Earth’s Crust
Study Guide
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Earthquake: The shaking and trembling of the crust that results from movement of rock
beneath the surface.
Fault: A crack in the crust where blocks of rock have slipped past each other.
Remember: " It's your Fault if you fall through a crack in the crust!"
Stress: A force that acts on a rock to change its shape or volume. The three types of stress are
shearing, tension, and compression.
Shearing: stress that slides or twists rock in opposite directions.
Tension: Stress that pulls rock apart.
Compression: Stress that squeezes rock together.
Rock that has been stressed is deformed. The process is called deformation.
Faults: Breaks or cracks in Earth’s crust. There are three types of faults:
Normal Fault: Hanging wall slips down while the foot wall stays in place.
Reverse Fault: Handing wall is pushed up while the foot wall stays in place.
Strike-Slip Fault: Rocks on either side of the fault slip past each other sideways, in opposite
directions.
Folds: these are bends in the rock that form when compression shortens and thickens Earth’s
crust. These are anticlines and synclines.
-Anticline: An anticline is a fold in rock that bends upward into an arch (EX: Ant hill)
-Syncline: A syncline is a folded rock that bends downward to form a “V” shape. (EX. Sinkhole)
Plateau: A large area of flat land that is elevated high above sea level. Forces in the crust push
the rock upwards.
Fault-Block Mountain: As the hanging wall of each normal fault slips downward, the block in
between now stands above the surrounding valleys.
Friction: The force that opposes the motion of one surface as it moves across another surface.