Deformation of the Crust2

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Deformation of the Crust : 

Deformation of the Crust Chapter 5 Notes

Slide 2: 

Deformation is responsible for many changes in the Earth’s surface including bending, tilting, and breaking. Isostasy – Balancing of the up and down forces acting on the Earth’s crust. Isostatic adjustment – The up and down movements of the Earth’s crust to reach isostasy.

Stress : 

Stress Stress – Force caused by Isostatic adjustment and continental plate movement

Strain : 

Strain Strain – Change in the shape and volume of rocks/crust caused by stress. Three main types: compression tension shearing

Folding : 

Folding Folding – Permanent deformation or bending of a rock under stress. Three main types of folds: Anticline – up curved fold in horizontal rock layers

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2. Syncline – down curved fold in horizontal rock layers

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3. Monocline – gently dipping bend in horizontal rock layer, may be one side of a syncline

Faulting/fracturing results from stress acting on the Earth’s crust. The rocks in the cooler portion of the crust near the surface are more brittle and break.

Fractures and Faults : 

Fractures and Faults Fracture – break in rock along which there is no movement Fault – break in rock along which rocks on either side of the break move

Parts of a Fault : 

Parts of a Fault

Normal Fault : 

Normal Fault Hanging wall is moving down relative to the footwall Tension Salt Lake City

Reverse Fault : 

Reverse Fault Hanging wall is moving up relative to the footwall Compression, Example the Redlands fault

Strike Slip Fault : 

Strike Slip Fault Foot wall and hanging wall move laterally relative to each other Shearing San Andreas Fault

Orogany : 

Orogany Most mountains are formed by plate collisions Continental crust and oceanic crust; The continental crust is deformed and the rock plate is partly melted due to friction, forming volcanic ranges. Also terranes. Example Cascade range

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Oceanic-oceanic collisions Subduction melts the rock into magma which forces up to form volcanoes on the ocean floor. Example Mariana Islands

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Continent-continent collisions Folded mountains landform created when tectonic movements bend and uplift rock layers crust is deformed and thrust up, example Himalayas

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Fault-block mountains Horst and Grabbens mountains formed where faulting breaks the Earth’s crust into large blocks and the blocks are uplifted and tilted Example Basin and Range

Basin and Range Fault Block Mountains : 

Basin and Range Fault Block Mountains

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Volcanic Mountains, magma erupts forming mountains, Cascades

Dome Mountains : 

Dome Mountains Dome Mountains, laccoliths, Black Hills, Adirondacks. Examples-La Sals

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Mountain range – group of adjacent mountains with the same general shape and structure ex.- San Juan Mountains

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Mountain system – group of adjacent mountain ranges ex.- Rocky Mountain system

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Mountain belt – group of large mountain systems ex.- Circum-Pacific mountain belt