Deforming the Earth’s Crust

1. Deformation - the process by which the shape of a rock changes because of stress is called deformation. Deforming the Earth’s Crust • compression: stress that occurs when forces act to squeeze an object at a convergent boundary.

2. Deforming the Earth’s Crust • tension: stress that occurs when forces act to stretch an object at a divergent boundary.

3. Folding • folding: the bending of rock layers due to stress. Deforming the Earth’s Crust - the three most common types of folds (pg.113) are: 1. anticline – upward arching folds

4. 2. syncline – downward channel-like folds Deforming the Earth’s Crust 3. monocline – both ends of the folds are horizontal in pattern

5. Faulting • fault: a break in a body of rock along which one block slides relative to another. Deforming the Earth’s Crust - fault blocks can be either hanging walls or footwalls.

6. 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)

7. Deforming the Earth’s Crust - when rocks are moved horizontally by opposing forces, strike-slip faults often form. (San Andreas Fault)

8. Plate Tectonics & Mountain Building - mountains exist because tectonic plates are continually moving & colliding with each other. Deforming the Earth’s Crust - 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

9. 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

10. 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

11. Deforming the Earth’s Crust Honolulu, Oahu Mauna Kea is the tallest mountain in the world at over 33,000 feet! The Hawaiian Islands are some of the youngest volcanic mountains forming right now.

12. 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

13. 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 form between two tectonic plates that are pulling away from each other