Transcript Chap7Sect4 - Cobb Learning

Chapter 7
Plate Tectonics
14 min. Plate Tectonics
Chap 7, Sec 4 (Deforming the Earth’s
Crust)
Objectives:
1. Review subduction. (yes, again!)
1. Describe the three types of stress
(force) that deform rocks.
2. Explain the differences between the
three major types of faults.
New 7.4 Tech Terms:
1. deformation – the change in the
shape of rock in response to
stress.
2. stress – a force that acts on rock
to change its shape or volume.
In the example above, the spaghetti deformed in two different ways—
by bending and by breaking. The same thing happens in rock layers. Rock
layers bend when stress is placed on them. But when enough stress is placed
on rocks, they can reach their elastic limit and break.
Rock faults occur when 3
types of stress are applied:
 shearing –when rock is
pushed in opposite directions
 tension - pulls on the crust,
stretching rock so it becomes
thinner in the middle
 compression – squeezes rock
until it folds or breaks
3 types of faults:
3. normal fault – tension creates
this fault at divergent
boundaries, causing rock to
pull apart (the footwall slides
up and the hanging wall slides
down). Occur along the Rio
Grande rift valley.
Normal Fault
4. reverse fault – compression
creates this fault at
convergent boundaries,
causing rock to compact (the
footwall slides down and the
hanging wall slides up).
Occurs along the Appalachian
Mountains.
Reverse Fault
5. strike-slip fault – shearing creates
this fault at transform boundaries,
which causes rock to slide past
each other in opposite directions.
Occurs along the San Andreas
Fault in California.
Strike Slip Fault
Let’s Summarize!
• ( Flip over your Bell-Ringer sheet)
• Read and do everything but landforms.
208-209
• musical review
• Landforms? 210-212 Mountains: 3 types
• Let’s label and color for review.
• Boundaries 20min