1. Stress, Faulting, Folding, Mountain Building
Inside Earth:

2. Have you ever tried to bend something, only to have it break?

3. How can material bend at one time and break at another?
The answer is that the stress you put on the material was different each time.
Stress is the amount of force per unit area on a given material.

4. This same principle applies to the rocks in the Earth’s crust
Different things happen to rock when different types of stress are applied.

5. Deformation
Deformation is the process by which a rock changes because of stress.
Rock layers bend when stress is placed on them.
When enough stress is placed on rocks, they reach their elastic limit and break.
There are two kinds of stress:
Compression
Tension

6. Compression This type of stress occurs when an object is squeezed.
Tectonic plates collide
When compression happens at a convergent boundary, large mountain ranges can form

7. Tension Another form of stress is tension.
Tension is the stress that occurs when forces stretch an object.
They occur at divergent boundaries.
Mid Ocean ridges

8. Folding
The bending of rock layers because of stress in the Earth’s crust is called folding.
Scientists assume that all rock layers started as horizontal layers.
When they see folding, they know that deformation has occurred
There are three types of folding: anticlines, synclines and monoclines

9. Anticlines
Upward arching folds

10. Synclines
Down-ward, trough-like folds

11. Monoclines
Rock layers are folded so that both ends of the fold are horizontal.

12. Faulting Some rock layers break when stress is applied to them.
The surface along which rocks break and slide past each other is called a fault.
The blocks of crust one each side of the fault is called a fault-block.

13. Not all faults are vertical…
And understanding the difference between it’s two sides, called hanging walls and foot walls is useful.
The type of fault that forms depends on how the hanging wall and foot wall move in relationship to each other.

14. Normal Faults
When a normal fault moves, it causes the hanging wall to move down relative to the footwall.
Normal faults usually occur when tectonic forces cause tension that pull rocks apart

15. Reverse Faults
When a reverse fault moves, it cause the hanging wall to move up relative to the footwall.
Usually happen when tectonic forces cause compression that pushes rocks together

16. Strike-Slip Faults
The third type of fault is called a strike-slip fault
These form when opposing forces cause rock to break and move horizontally.
The San Andreas fault is a strike-slip fault

17. Plate Tectonics and Mountain Building
When tectonic plates collide, land features that start as faults and folds can eventually become large mountain ranges.

18. Mountains exist because tectonic plates are constantly moving around
As a result of this movement, they collide with each other.
Mountains, such as the Andes Mountains in South America, form in the subduction zone where two tectonic plates converge.

19. Mountains are formed in several ways
The three most common types of mountains are classified by the way they were formed
Folded Mountains
Fault-Block Mountains
Volcanic Mountains

20. Folded Mountains
Formed at the convergent boundaries where the continents have collided.
Formed when rock layers are squeezed together and pushed upward.
The highest mountain ranges in the world
Appalachians
Himalayas

21. Fault-Block Mountains
Form when tension pulls on large blocks of the Earth’s crust to drop down relative to other blocks.
Sharp, jagged peaks
Grand Tetons in Wyoming

22. Volcanic Mountains
Most of the world’s major volcanic mountains are located at convergent boundaries.
Ring of Fire!
They form when magma rises to the Earth’s surface and erupts, forming a volcanic mountains.
Can also be found underwater

23. Uplift and Subsidence
Vertical movements in the Earth’s crust are divided into two types.
Uplift: created by the rising of the Earth’s crust to higher elevations
Subsidence: The sinking of the Earth’s crust to low.er elevations

24. Compression Th