Deforming of the Earth’s crust Compiled by Woodruff Using Holt Earth Science Text
Deformation of Earth’s crust • Deformation: the shape of a rock changes due to stress • Types of stress: • Compression: stress caused when objects are squeezed together. Occurs where tectonic plates collide. • Tension: stress caused when objects are stretched. Occurs where tectonic plates move apart.
Folding in the Earth’s Crust • Folding: the bending of rock layers caused by stress. • Types of folding: • Anticlines: upward-arching folds in rock • Synclines: downward, through-like folds in rock • Monocline: folded rock layers where both ends of the fold are horizontal.
Faulting of the Earth’s Crust • Fault: the surface along which rocks break and slide past each other. • Fault block: the blocks of rock on either side of a fault. • Footwall: Fault block with more rock at the bottom of the fault block. You could walk up this block. • Hanging wall: Fault block with more rock at the top of the fault block. You could hang from this block.
Types of faults: • Normal Fault: Hanging wall moves down relative to the footwall. Caused by tension at the fault.
Types of faults: • Reverse Fault: the hanging wall moves up relative to the footwall. Caused by compression at the fault.
Types of faults: • Strike-Slip Fault: when fault blocks break and move horizontally to each other.
Mountain Building: • Folded mountains: formed when rock layers are squeezed together and pushed upwards. Example: Himalayan Mountains. Wet Graham Crackers.
Mountain Building: • Fault Block Mountains: Formed when tension causes large blocks on the surface to drop down relative to other blocks. Example: Grand Tetons in Wyoming.
Mountain Building: • Volcanic Mountains: Usually form at convergent boundaries, but can also form in the ocean. Pacific Ring of Fire has lots of volcanoes!
Vertical Movements of Earth’s Crust • Uplift: The rising of regions of the Earth’s Surface. Caused by many different factors including rebound: when a block uplifts because pressure from above has been removed. • Subsidence: the sinking of regions of the crust to lower elevations. Caused by blocks being pulled apart or rocks cooling down.