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Ch. 7 Section 4 Outline/Notes Deforming the Earth’s Crust
I. What is stress?
Stress is the amount of __________________ per unit of area that is put on a given material.
II. Rocks Get Stressed
A. Compression- stress that occurs when an object is ___________________________________
B. Tension- a stress that occurs when forces act to ____________________________________ an object.
C. compression and tension bend and break rock to form some of the common _______________________
you already know
III. Folding
A. Folding-
1. anticline2. syncline- landform created when stress bends or folds a rock downward
IV. Faulting
A. Fault- the surface along which rocks break and slide past _____________________________
B. Normal Fault-
C. Reverse Fault- movement of a reverse fault causes the hanging wall to move up relative to the footwall
(the reverse of a normal fault)
D. Strike-slip fault- occur when opposing forces cause rock to break and move horizontally.
V. Plate Tectonics & Mountain Building
A. When plates collide, land features that start out as small folds and faults can eventually become
great ______________________________________________
B. Folded Mountains-
B. Fault-block Mountains- when tectonic force put enough tension on Earth’s crust, a large number
of normal faults can result. Fault-block Mountains form when this
faulting causes…____________________________________________
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Continental Collision
How did rocks that formed on sea floors and islands become the mountains and valleys of today? The ocean that
formed during the continental breakup about 540 million years ago continued to expand. During that time
bacteria, algae, and many species of invertebrates flourished in the oceans, but there were no plants or animals
on land. Then, about 470 million years ago, the motion of the crustal plates changed, and the continents began to
move toward each other (fig. 13). As the continental plates moved closer together, fragments of oceanic crust,
islands, and other continental masses collided with the eastern margin of ancient North America. By this time,
plants had appeared on land, followed by scorpions, insects, and amphibians. The ocean continued to shrink
until, about 270 million years ago, the continents that were ancient to North America and Africa collided. Huge
masses of rocks were pushed west-ward along the margin of North America and piled up to form the mountains
that we now know as the Appalachians.
1. What type of mountains are the Appalachians? _________________
2. Describe how the Appalachians formed? ______________________
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