Presentation on theme: "Deforming the Earth’s Crust. Stress The amount of force per unit of area on a given material."— Presentation transcript:
Deforming the Earth’s Crust
Stress The amount of force per unit of area on a given material.
Deformation The process by which the shape of a rock changes because of the stress on it.
Compression The type of stress that occurs when an object is squeezed, such as when two plates collide.
Tension The type of stress that occurs when forces act to stretch an object such as at a divergent boundary.
Folding The bending of rock layers because of stress in the Earth’s crust.
Anticlines and Synclines Anticlines – Upward arching folds in rock layers Synclines – Downward, trough-like folds in rock layers
Fault The surface along which rocks break and slide past each other The blocks of crust on each side are called fault blocks.
Hanging Wall and Foot Wall
Normal Fault The hanging wall moves down relative to the footwall. Usually occur under tension (divergent boundary)
Reverse Faults The hanging wall moves up relative to the footwall. Usually occur under compression (convergent boundary)
Strike –Slip Fault When opposing forces cause rock to break and move horizontally. The San Andreas fault in California is an example.
Folded Mountains The tallest mountains in the world are made of folded mountains. Form at convergent boundaries Examples: –Appalachian Mountains (North America) –Alps (Europe) –Ural Mountains (Russia) –Himalayas (Asia)
Fault-Block Mountains When tension causes large blocks of the Earth’s crust to drop down relative to other blocks. Example: Tetons in western Wyoming
Volcanic Mountains Continued… Most are located at convergent boundaries where oceanic crust sinks into the asthenosphere at subduction zones. The rock is melted, forms magma, then rises to the surface and erupts to form volcanic mountains.
Ring of Fire The majority of tectonically active volcanic mountains on the Earth have formed around tectonically active rim of the Pacific Ocean. This has been known as the “Ring of Fire”.
Uplift and Subsidence Uplift - The rising of regions of Earth’s crust to higher elevations. Subsidence – The sinking of Earth’s crust to lower elevations.