1. Deforming the Earth’s Crust Faults and Folds
Chapter 7 Section 4

2. Deformation
The process by which the shape of a rock changes because of stress.
There are two types of stress that occur in rocks:
Compression
Tension

3. Compression Compression occurs when rock is squeezed.
Compression happens when two plates collide at a convergent boundary.
Compression occurs and forms large mountain ranges.

4. Compression/ Mountain Building
The Himalayas, for example, were raised by the compression that accompanied collision of the Indian plate with the Eurasian plate. Another example is Europe's Alps and Jura mountains which were also formed by horizontal compression, generated in their case by collision with the African plate and the Eurasian plate.

5. Tension Tension occurs when an object is stretched.
Tension occurs when plates move away from each other at plate boundaries.
At the Mid-Atlantic ridge the seafloor is spreading at a rate of about 3cm per year. The frequency of earthquakes at a mid-ocean ridge will depend on how much tension is happening at that point. The more tension means the more seafloor spreading, resulting in a higher frequency of earthquakes at a particular mid-ocean ridge.

6. Folding
Folding is the bending of rock layers due to stress in the Earth’s crust.
Depending on how rock layers deform, different types of folds occur:
Anticline
Syncline
Monocline

11. Anticline An anticline is an upward-arching fold.
An anticline is formed when there is horizontal stress on rock layers.
Horizontal stress

12. Syncline Synclines are downward folds.
They are also caused by horizontal stress.
Horizontal Stress

13. Monocline
Monoclines are rock layers that are folded so that both ends of the fold are horizontal.

14. Faults Some rock layers break when stress is applied to them.
The surface along which rocks break is called a fault.
The blocks of crust on each side of the fault are called fault blocks.
A fault has a foot wall and a hanging wall.

15. Footwall
Footwall
You could walk up this face of the fault, on foot, hence the name footwall.

16. Hanging Wall You could hang from this wall. Hanging Wall
This is a normal fault. Notice how the rock layers are the same at the red lines.

17. Hanging wall and Footwall

18. 3 Types of Faults
Normal Fault
Reverse Fault
Slip-Strike Fault

19. Normal Fault Rocks are pulled apart because of tension. Hanging wall
Footwall
In a normal Fault, the hanging wall slides down the footwall.

22. Reverse Fault
In a reverse fault the hanging wall is pushed upward due to compression.

25. Strike-Slip Fault
Opposing forces cause rocks to move horizontally. Earthquakes occur along these faults.

28. San Andreas Fault, California Strike-Slip Fault

29. 3 Most Common Types of Mountains
Mountains exist because tectonic plates are continually moving around and colliding with each other.
There are 3 types of mountains, named for how they form:
Folded Mountains
Fault-Block Mountain
Volcanic Mountain

30. Folded Mountains
Folding is a process in which the Earth's plates are pushed together in a roller coaster like series of high points and low points. Folding bends many layers of rocks without breaking them. The Appalachian Mountains and Rocky Mountains of the United States, and the Alps of Europe are examples of mountain ranges that were formed by folding. Folded Strata (Layers)

31. Fault- Block Mountains
Mountains sometimes form when many layers of the Earth's crust are moved vertically upward at fault lines by pressures caused by plates colliding. Fault lines are great cracks in the crust. The mountains that are formed in this way are called fault-block mountains. The Sierra Nevada mountains in California and Nevada, and the Grand Teton range of Wyoming are examples of fault-block mountains.
Fault block mountains form when tension causes large blocks of crust to drop down relative to other blocks.

32. Volcanic Mountains
Volcanic mountains are forms when magma erupts from a divergent boundary and hardens.
Many volcanic mountains exist under the sea.
Some volcanic mountains rise above the surface of the ocean to from islands, Hawaii for example.

33. Hawaiian Islands