1. Forces in EARTH’s Crust
Inside Earth Ch. 2.1
Forces in EARTH’s Crust
Intro to Earthquakes: (3:56)
History of the Earth: (2:11)

2. Introduction
What is stress?

3. Stress?
Science Stress is = A force that acts on rock to change its shape or volume
Health Stress can also be = Something that causes strong feelings of worry or anxiety

4. I. Types of Stress A. Tension, _Compression_, Shearing
B. These forces cause _rock_ to snap
C. Changes occur really _slowly_
D. Rock can bend, _stretch_ tilt, _fold_or slide

5. I. Types of Stress
E. Tension = pulls on crust so it’s thinner in middle, 2 plates move apart
F. Compression = squeezes rock until it folds or breaks, 1 plate pressing against another
G. Shearing = pushes rock in 2 opposite directions, 2 plates slip past each other
Forces Video (3:11)

6. Types of Stress

7. II. Kinds of Faults Most faults occur along _plate_ _boundaries.
A. Normal Faults are caused by _tension_,
normal fault= Hanging wall slips down
hanging wall = rock that lies above
footwall = rock that lies below
Types of Faults video:

8. Faults

9. II. Kinds of Faults B. Reverse Faults are caused by compression.
Hanging wall moves up over the footwall.
C Strike-Slip Faults are caused by _shearing_ .
1. 2 plates slip past each other, very little up/down motion

10. Strike Slip Fault

11. III. Earth’s Changing Surface
A. Folding Earth’s Crust
_Plate_ _movement_ can cause crust to fold due to _compression_.
Anti-cline = a fold in the rock that bends upward
Syncline = a fold in the rock that bends downward

12. Anticlines and Synclines

13. B. Stretching Earth’s Crust
Tension pulls crust apart, 2 parallel normal faults can form a range of _fault_ - _block_ mountains.

14. C. Uplifting Earth’s Crust
Plateau = large area of flat land elevated above sea level
Deformation = any change in the volume or shape of the Earth’s crust due to stress
Friction = the force that opposes the motion of one surface as it moves across another surface
Plate Tectonics Song (3:45)