Deforming the Earth’s CrustDeformation

- the process by which the shape of a rock changes because of stress is called deformation.

compression: stress that occurs when forces act to squeeze an object at a convergent boundary.

Deforming the Earth’s Crust

tension: stress that occurs when forces act to stretch an object at a divergent boundary.

Deforming the Earth’s CrustFolding

folding: the bending of rock layers due to stress.

- the three most common types of folds (pg.113) are:

1. anticline – upward arching folds

Deforming the Earth’s Crust2. syncline – downward channel-like folds

3. monocline – both ends of the folds are horizontal in pattern

Deforming the Earth’s CrustFaulting

fault: a break in a body of rock along which one block slides relative to another.

- fault blocks can be either hanging walls or footwalls.

Deforming the Earth’s Crust

- when normal rocks are pulled apart because of tension, normal faults often form. (African Rift)

- when rocks are pushed together by compression, reverse faults often form. (Himalayas & Alps)

Deforming the Earth’s Crust

- when rocks are moved horizontally by opposing forces, strike-slip faults often form. (San Andreas Fault)

Plate

Plate

Deforming the Earth’s Crust Plate Tectonics & Mountain Building

- mountains exist because tectonic plates are continually moving & colliding with each other.

- three most common types of mountains are:

1. folded mountains (pg.116) – these form when rock layers are squeezed together & pushed upward.

Ushuaia, Argentina Matterhorn, Switzerland

Deforming the Earth’s Crust

2. fault-block mountains (pg.117) – these form when tension causes large blocks of the Earth’s crust to drop down relative to other blocks.

Grand Tetons, Wyoming

Deforming the Earth’s Crust

3. volcanic mountains (pg.117) – these form when rock that is melted in subduction zones forms magma, which rises to the Earth’s surface through eruptions.

Mount Fuji, Japan

Mount St. Helens, Washington

Deforming the Earth’s Crust

Mauna Kea is the tallestmountain in the world atover 33,000 feet!

Honolulu, Oahu

The Hawaiian Islands are some of the youngest volcanic mountains forming right now.

Deforming the Earth’s Crust Uplift and Subsidence

uplift: the rising of regions of the Earth’s crust to higher elevations.

subsidence: the sinking of regions of the Earth’s crust to lower elevations.

- rocks that subside do not undergo much deformation

Deforming the Earth’s Crust

- subsidence can also occur when the lithosphere becomes stretched in rift zones.

- rift zones are sets of deep cracks that formbetween two tectonicplates that are pulling away from each other