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Chapter 10 The Movement of the Earth’s Crust. The forces within the Earth push and pull on the Earth’s Crust. Think back to Section 9.3 The Earth’s Crust. The Earth’s crust moves as a result of the stress or forces within the Earth. Which brings us to Chapter 10 - PowerPoint PPT Presentation
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Chapter 10 The Movement of the Earth’s
Crust
THE FORCES WITHIN THE
EARTH PUSH AND PULL ON THE
EARTH’S CRUST.
Think back to Section 9.3The Earth’s
Crust
The Earth’s Crust:
Continental Crust
Oceanic Crust.
Continental Crust av. 32 km
Oceanic Crust av. 8 km
The Earth’s crust moves as a result of the stress or forces within the Earth.
Which brings us toChapter 10
The Movement of the Earth’s Crust
Stressare forces that push and pull on the Earth’s crust causing it to undergo deformation.
As rocks under go
stress
They slowly change
shape and volume
Also, they move up
and down
The movement causes the
rocks to break, tilt, and fold.
Deformation is the
breaking, tilting, and folding of
rock.
StressCauses rocks to slowly
change shape and volume.
3 Types of Stress
Compression Tension Shearing
Compression
Tension
Shearing
Compression, tension, and shearing of rocks
can cause the rocks to
Fracture or crack.
Fault
Break or crack along which rocks move
Large faults within the Earth’s crust result from the movement of tectonic plates
A Normal Fault occurs when tension or pulling apart acts on a fault. The hanging wall will move down
relative to the foot wall.
Tension
A Reverse Fault occurs when compression or pulling apart acts on a fault causing the hanging wall to
move up relative to the foot wall.
Compression
Thrust Fault is a special type of reverse fault that is formed when compression causes the hanging wall to
slide over the foot wall.
A lateral fault occurs when shearing acts on a fault which causes blocks of rock to slide horizontally past each other left or right.
Shearing
Fault-block mountains are formed by blocks of rock uplifted by 2 normal faults.
Example: Cordilleran Mountains in Western USA
Fault Block Mountain
Rift Valleys
are formed by 2 normal faults sliding down
Example: Death Valley, California USA
Nearly five and a half million years ago, what we today call Baja California used to be part of the Mexican mainland, and then it began pulling away as tectonic forces underneath split the land apart. Now, Baja California is slowly moving northwest. Some geology experts say that the northernmost extension of this rift, or tear, is the area we call Death Valley, while others claim it to be in the Salton Sea. There is even some plausible scientific evidence to support the idea that this tearing of the land could extend as far north as southern Oregon. There are those who refer to this phenomenon as the Baja Rift.
A fold is a bend in rock.
Anticline is an upward fold.
Syncline is a downward fold.
Factors that will determine whether rocks will fault or
fold
Temperature•Hotter: Folds
Pressure•Greater: Fold
Rock type•Brittle: Fault•Ductile: Fold
How Stress Applied•Gradually: Fold•Suddenly: Fault
Plateau may be formed by:
Slow flat topped fold
Appalachian Plateau
Vertical faulting
Colorado Plateau
Molten lava flows on surface of Earth
layer by layer
Rivers often carve a large plateau into
smaller plateaus
Grand Canyon in Colorado
Plateau
Vertical Fault
Plateau
Plateau: Top of Volcano
Grand Canyon in Colorado Plateau
Magma – molten rock beneath the Earth’s Surface
Lava - molten rock beneath the Earth’s Surface
Dome – oval or circular uplift by rising magma, fluid collects beneath the surface and pushes up like a blister
Dome Mountains – domes that have been worn away in some places leaving separate peaks