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Chapter 7 Plate Tectonics
Section 4 Deforming the Earth’s Crust
Standards:
S6E5.d: Describe processes that change rocks and the surface of the Earth.
S6E5.e: Recognize that lithospheric plates constantly move and cause major geological events on the Earth’s
surface.
S6E5.f: Explain the effects of physical processes (plate tectonics) on geological features including oceans.
I. Deformation
A. Stress: the amount of force per unit area on a given material.
B. Deformation: the process by which the shape of a rock changes because of stress.
C. Compression: the type of stress that occurs when an object is squeezed, such as when two tectonic
plates collide. It occurs at a convergent boundary.
D. Tension: stress that occurs when forces act to stretch an object. They occur at divergent boundaries
such as mid-ocean ridges.
II. Folding
A. Definition: the bending of rock layers because of stress in the Earth’s crust.
B. Types of Folds
1. Anticlines: upward arching folds
2. Synclines: downward, troughlike folds
3. Monoclines: both ends form horizontal
III. Faulting
A. Definition: the surface along which rocks break and slide past each other
B. What are the two sides called? Hanging wall and footwall
C. What are the three types of faults?
1. Normal Fault: the hanging wall moves down relative to the footwall. This is caused by
tension.
2. Reverse Fault: the hanging wall moves up relative to the footwall. This is caused by
compression.
3. Strike-Slip Fault: form when opposing forces cause rock to break and move horizontally.
IV. Plate Tectonics and Mountain Building
A. Folded Mountains: form when rock layers are squeezed together and pushed upward. They form
at convergent boundaries.
B. Fault-Block Mountains: form when this tension causes large blocks of the Earth’s crust to drop down
relative to other blocks.
C. Volcanic Mountains: the rock that is melted in Subduction zones forms magma, which rises to Earth’s
Surface and erupts to form volcanic mountains.