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MOUNTAIN BUILDING –student notes 1. ______________ – refers of all changes in the original shape or size of a rock body. ______________ deformation – at the earth’s surface, low temperatures and low pressures, solid rock fractures ______________ deformation – deep with in the Earth, high temperatures and high pressures, rock is deformed without breaking The mineral composition and texture also affects how it will deform. Small stresses applied over time will cause the rock to bend. 2. Stress and Strain ______________ – force per unit area acting on a solid ______________ – the change in shape or volume ______________ stress – causes a material to be stretched ______________ stress – causes a material to shorten ______________ stress – causes a material to be distorted 3. Folds – during mountain building flat-lying sedimentary and igneous rock are bent into a series of ripples ______________ – arching of rock layers ______________ – downfolds or troughs ______________– large step-like folds 4. Faults – fractures in the crust along which movement has taken place ______________– when the hanging wall block moves down relative to the footwall block, caused by tensional forces ______________– the hanging wall block moves up relative to the footwall, caused by compressional forces ______________– reverse faults with dips less than 45o ______________faults – the movement is horizontal and parallel, caused by shear stress, San Andreas fault ______________ – most common rock structure, fractures along which no appreciable movement has occurred 5. Mountains – classified by the dominant processes that deformed them ______________ Mountains – formed by folding, ______________ stress is the major force that formed them; examples – Appalachians, Alps, northern Rocky Mountains ______________Mountains – mountains that form as large blocks of crust are uplifted and tilted along normal faults; examples – Tetons Range, Sierra Nevadas Horst and Grabens – formed from tensional forces, horsts are uplifted structures and grabens is where the blocks dropped down; example – the Basin and Range region of Nevada, California and Utah ______________ – formed by upwarping and exposing older igneous and metamorphic rock; example – Back Hills of South Dakota Basins – downwarping structures having a circular shape 6. Mountain Building – ______________ Mountain Building at Convergent Boundaries – colliding plates provide the compressional forces that deform rock Oceanic-Oceanic Convergence – forms ______________arcs, Aleutian Islands of Alaska Ocean- Continental Convergence – ocean crust subducts the continental crust, the continental crust is deformed, creates volcanic arcs on continent Accretionary wedge – accumulation of different sedimentary and metamorphic rocks Continent-Continent Convergence – form ______________ mountains; examples – Himalayas, Ural mountains Mountain Building at Divergent Boundaries – fault-block mountains Non-Boundary Mountains – Hawaiian Islands are volcanic islands formed by a ______________ Continental Accretion – smaller crustal fragments collide and merge with continental margins; example – many of mountains rimming the Pacific Canada and Alaska ______________ – any crustal fragment that has a geologic history distinct from adjoining terranes ______________ – a floating crust in gravitational balance. As mountains erode, the crust rises in response to the reduced load. Erosion and uplift continue until the mountains reach normal crustal thickness The weight of the ice sheet during the Pleistocene depressed the Earth’s crust hundreds of meters. Since the ice age, uplift has occurred DRAWINGS: