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WHAT IS OROGENY? Processes of mtn building Distinctive patterns of deposition eugeocline, miogeocline Deformation Folding and thrust-faulting Metamorphism Intrusions: batholiths, etc Volcanic Activity TYPES OF MOUNTAINS • • • • Volcanic: Shield and composite Fault-block: normal faulting and tension Folded: reverse faults and compression Complex: mixture of most of the above Mauna Loa in Background Kilaeua is Behind Mauna Loa Mauna Kea Shield volcano Hot Spot Basalt Kilaeua Newest ground in The world Asthenosphere coming To the surface Composite Volcano Mt Rainier Compressive forces Subduction zones Andesitic composition Guagua Pichincha, Ecuador Quito in foreground Composite volcanoes explosive Normal fault Footwall moves Up relative to Hanging wall FOOTWALL HANGING WALL Tension forces Tilted fault-block range: Sierra Nevada from east, Steep side of block fault; Ansel Adams photo Tilted Fault-block Sierra Nevada from west Side, low angle Yosemite valley the result Of glaciation on low-angle relief Wasatch Range From Salt Lake City Typically faultBlock system Grand Tetons: Another fault-block system Alternating normal faults lead to a characteristic pattern called a Horst and Graben system. An area under tension will often have Multiple mountain ranges as a result. Basin and range province: tilted fault-block mountains in Nevada. The results of a horst and graben system. Nevada is under tension Because of rising magma which is unzipping the system, all the way From Baja California Sierra Nevada and Wasatch Ranges part of this system REVERSE FAULTS: Hanging wall moves up relative to footwall Result of compression: plates colliding Two types: low-angle or thrust faults, and high-angle reverse faults Individual layers can move 100’s of kilometers Alps are a great example Thrust faults main cause Of folded mountains Appalachian Mountains of the US Atlas Mountains, Northern Africa Classic folded terrain: well-developed anticline ZAGROS MTS PERSIAN GULF Alternating Anticlines and Synclines High-angle reverse faults Forms “Sawtooth Mtns” Flatirons classic example Sawtooth effect result of Differential erosion SAWTOOTH RANGE, IDAHO Alice Lake White Cloud peak COMPLEX MOUNTAINS Tend to have a little of Everything: volcanoes, Folds, thrust faults, normal faults ALPS HIMALAYAS
