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MOUNTAIN BUILDING. MOUNTAIN FORMATION 1. orogeny = processes that form all mountain ranges a. creates broad, linear regions of deformation known as orogenic belts b. most belts are associated with plate boundaries
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MOUNTAIN BUILDING MOUNTAIN FORMATION 1. orogeny = processes that form all mountain ranges a. creates broad, linear regions of deformation known as orogenic belts b. most belts are associated with plate boundaries 2. mountains = natural landforms that reach high elevations a. usually have narrow summits and steep slopes b. rise at least 600 meters above the surrounding land Saladian Orogeny
3. mountain range = group of adjacent mountains with same general shape and structure Ex: Mount St. Helens is part of Cascade Range 4. mountain system = group of adjacent mountain ranges Ex: The Great Smoky, Blue Ridge, Cumberland, and Green mountain ranges = Appalachian mountain system in eastern United States Antarctic Mountain range
5. mountain belt = large group of mountains including mountain ranges and mountain systems a. two major belts 1) Circum-Pacific belt = rings Pacific Ocean 2) Eurasian-Melanesian belt = runs across northern Africa, southern Europe, and Asia b. both meet in Indonesia, just north of Australia c. both belts are located along convergent plate boundaries
6. form when plates collide a. continental and ocean plate b. two ocean plates c. two continental plates 7. continental margin = boundary between continental crust & oceanic crust a. two types: 1) active = occur along plate boundaries 2) passive = do not occur at plate boundaries b. mountain building takes place near active margins
Changes in Earth’s Crust: 1. due to weight (addition or removal) of some part of crust a. when thicker and heavier will sink more into mantle b. when thinner and lighter will rise higher on mantle 2. up and down movements occur because of two opposing forces a. crust presses down on mantle b. mantle presses up on crust c. forces are balanced crust does not move up or down
3. isostasy = balancing of two forces a. isostatic adjustments = up and down movements of crust to reach isostasy b. during adjustments areas of crust are bent up and down c. pressure created causes rocks in that area to deform d. occurrences areas 1) constantly in areas with mountain ranges 2) where rivers flow into large bodies of water carrying large amounts of sediment 3) where glaciers once covered the land
4. principle of isostasy = parts of crust will rise or subside until these parts are buoyantly supported by their roots a. mountain ranges have thick roots of continental material that extend into mantle b. as mountains erode and mass becomes smaller, roots will become smaller c. balance between erosion and decrease in size of root will continue for hundreds of millions of years until both mountains and their roots disappear 5. isostatic rebound = slow process of crust’s rising as result of removal of overlying material
deformation = bending, tilting, and breaking of earth’s crust Types of Mountains 1. folded mountains = rock layers buckle and fold due to being squeezed from opposite sides a. highest mountain ranges in the world b. show evidence of faulting and igneous activity Ex: Appalachian Mountains (oldest in North America) Himalayas, Alps, Ural Mountains Himalayas
2. fault-block mountains = crust is broken into large blocks and lifted above surrounding crust a. faulting tilted blocks form gently sloping mountains b. one block is pushed up while the other block is pushed down Ex: Grand Teton Mountains, WY c. grabens = long, narrow valleys formed when large blocks of crust have dropped between normal faults Ex: Death Valley, CA Yosemite
d. horsts = forms when block of crust is thrust upward between two normal faults Ex: Basin and Range Province of Nevada e. ocean ridge mountain ranges can be thousands of km wide f. pillow basalts = igneous rock formed when magma pushes through dikes and erupts onto seafloor Located in Nevada
3. volcanic mountains = when molten rock erupts onto surface a. develop on land or ocean floor b. largest found on divergent plate boundaries of mid-ocean ridge c. peaks can rise above sea level to form volcanic islands d. hot spots = pockets of magma beneath crust that erupt onto surface Ex: Mt. St. Helens, WA [land] Mauna Loa, Hawaii [hot spot] Iceland [volcanic island] Mt. Baker
4. dome mountains = molten rock rises through crust and pushes up rock layers above it a. forms a circular dome on earth’s surface b. also referred to as uplifted mountains c. isolated structures that tend to occur in areas of essentially flat-lying sedimentary rocks d. eventually rock wears away in places leaving separate high peaks Ex: Black Hills, SD Adirondack Mountains, NY Yellowstone
