Geography Chapter 14 Notes PDF

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Geography Chapter 14 Notes The Internal From rigid Earth to Plate tectonics Continental millions of years ago there existed a supercontinent, Pangea, which separated into the present day continents. Evidence for Continental Drift Close geological features on the sides of the continents Rock records ...

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Geography Chapter 14 Notes The Internal Processes● From rigid Earth to Plate tectonics ○ Wegener’s Continental Drift- millions of years ago there existed a supercontinent, Pangea, which separated into the present day continents. ■ Wegener’s Evidence for Continental Drift ● Close geological features on the sides of the continents ● Rock records were similar across continents ● Fossils of similar species were found on different continents ■ Rejection of Continental Drift ● Many people didn’t believe ● Believed the Earth’s crust was too rigid for movement ● Wegener didn’t supply a method to the movement of the crust. ● Theory of Plate Tectonics ○ The Evidence ■ 1957- first map of the ocean floor and the underlying crust ● Found sea volcanos and other features on the sea floor, indicating crust movement ■ Discovery of the midocean ridge ■ Development of seismographs ○ Seafloor Spreading- the theory state that midocean ridges are formed by currents by magma rising up from the mantle and that volcanic eruptions create new basaltic ocean floor, which then spreads away laterally from the ridge. ● Subduction- older lithosphere descends into the asthenosphere in this process. ■ Verification of Seafloor Spreading ● Paleomagnetism- was used to prove that new crusts were formed due to a relatively symmetrical pattern of magnetic orientation. ● Analysis of ocean floor cores ○ Plate Tectonic theory- the explanation as to the movement of the Earth’s plates. ● Lithosphere- rigid plates floating over the asthenosphere. ○ There are 7 major plates, with over 12 smaller plates. ■ Mechanism for plate tectonics ● Convection within Earth’s surface--- “much of the motion is a result of the plates being pulled along by the subduction of cooler, denser oceanic lithosphere down to the asthenosphere.” ● Plate Boundaries ○ Divergent Boundaries- magma from the asthenosphere rises up between the plates, leading to the production of volcanic activity ■ Mid ocean ridges- representation of a divergent boundary; areas of small earthquakes and volcanic activity. ■ Continental Rift valleys- divergent boundaries located within a continent.

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Convergent Boundaries- the location where plates collide; responsible for mountain ranges, volcanoes, and oceanic trenches. ■ Oceanic-Continental Convergence ● Oceanic crust subducts under the lithospheric crust ● Location of many earthquakes and volcanoes ■ Oceanic-Oceanic Convergence ● One oceanic plate subducts under another and ■ Continental-Continental Convergence ○ Transform Boundaries ■ Two plates slip past one another laterally, usually found along midocean ridge systems. ○ Plate Boundaries over Geologic Time ● Provide us with the framework for understanding the extensive lithospheric rearrangement that has taken place during the history of the Earth. ■ Plate Motion into the Future ● Australia will move over the equator as a tropical island ● Africa would pinch shut the mediterranean ● Atlantic will widen while the pacific shrinks ● California will break apart. ○ Cordillera- groups of mountains ■ The Pacific Ring of Fire ● The location in the pacific ocean where large amounts of volcanic activity occurs (Mexico City, Los Angeles, Tokyo) ○ Most recent large scale activity was Mt. St Helen’s Additions to Tectonic Plate Theory ○ Hotspots and Mantle plumes ■ Explaining Hot Spots ● Mantle Plume- a model demonstrating that midplate volcanic activity develops over narrow plumes of heated material rising through the mantle, originating as deep as the core-mantle boundary. ■ The Hawaiian Hot Spots ● Due to their location on the a fault, the Hawaiin Islands are formed from volcanic activity due to the continuous flow of a mantle plume to the surface of the sea floor. ■ Accreted Terranes ● Terrane- a small to medium mass of lithosphere--- bounded on all sides by faults--- that may have been carried a long distance by a moving plate, eventually to converge with another plate. ○ Too buoyant to subduct in the collision and therefore is fused to the other plate instead, ■ Remaining Questions

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Volcanism- a general term that refers to all the phenomena connected with the origin and movement of molten rock. ○ Volcano Distribution- generally associated with plate boundaries and hot spots. ■ Volcanic Activity ● Active volcano- a volcano that has erupted at least once in recorded history and is likely to do so again. ○ Magma Chemistry and Styles of Eruption ● Magma- motlen mineral material below the surface ● Lava- magma that comes to the Earth’s surface. ● Pyroclastics- solids rock fragments dispersed during a volcanic blasts. ■ Felsic magmas- cooler, high-silica content, and thick, slow moving lava prone to explosions due to the high content of gases trapped in the substance. ■ Mafic Magmas- Hotter, low-silica content, resulting in efflusive eruptions without explosions or many pyroclastics. ■ Intermediate Magmas- Intermediate silica content, periodic flow of lava and pyroclastics ○ Lava Flows ■ Columnar Basalt- when lava flows cool uniformly , it contracts and forms a distintive pattern of vertical columns. ■ Flood Basalt- the accumulation of lava that builds up layer upon layer. ○ Volcanic Peaks ■ Shield Volcanoes- gently sloping mountain formed by layers of solidified lava flow with basaltic lava and effusive eruptions of fluid lava ● Hawaiin Islands ■ Composite volcanoes- Steep sided symmetrical cones consisting of flowing lava, pyriclastics, and hardened volcanic mudflow deposits with both effusive and explosive eruptions of lava and pyroclastic material. ● Mt. Saint Helen ● Mt. Fuji ● Lava Domes- typically small with irregular shapes, with viscous flowing lava covered by pyroclastics often found within a crater of composite volcanoes. ○ California ■ Cinder Cones- small steep sided cones with loose pyroclastic material ● Mexico, Arizona ■ Calderas- produced when a volcano explodes, collapses, or both. Immense basi-shaped depression ● Crater Lake in Oregon. Volcanic Hazards ○ Volcanic Gases

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Can include water vapor, carbon dioxide, sulfur dioxide, hydrogen sulfide, and fluorine.Can produce acid rain, pockets of CO2. ○ Lava Flows ○ Eruption Column and Ash Fall ○ Pyroclastic Flows ■ Terrifying high speed avalanche of searing hot gases, ash, and rock fragments. ○ Volcanic Mudflows ■ A loose mantle of ash and pyroclastics can be mobilized by heavy rain or by the melting of snow or ice. ○ Monitoring volcanoes ■ Eruption of Mount Saint Helen Intrusive Igneous Features ○ Plutons- a general term used to refer to intrusive igneous bodies of nearly any size that disturb the preexisting rock ■ Batholiths- subterranean igneous body of enormous size… often responsible for the core of mountain ranges. ■ Volcanic necks- remnant of a pipe, or “throat” of an old volcano that filled with solidified lava after its final eruption. ■ Laccoliths- develops when viscous felsic magma is forced between horizolntal layers of preexisitng rock., forming a mushroom shaped mass that domes the preexising strata. ■ Sills- long, thin intrusive body formed when magma, typically basaltic, is forced between strata. ■ Dikes- formed by the intrusion of a vertical rock ■ Veins Tectonism: Folding ○ The Process of Folding- when crustal rocks are subjected to stress, particularly lateral compression, they can be deformed by being bent in a process called folding. ○ Types of Folds ■ Monocline- a one sided fold, a slope connecting two horizontal or gently inclined strata. ■ Anticline- simple symmetrical upfold ● Overturned fold- occurs when an upfold is pushed extensively from one side. ● Overthrust fold- occurs if the pressure is great enough to break overturned fold and cause a shearing movement. ■ Syncline- simple symmetrical downfold ○ Topographic features Associated with Folding ■ Anticlinal Ridge ■ Anticlinal Valley ■ Synclinal Valley

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■ Synclinal Ridge Tectonism: Faulting- when a rocks structure is broken and one side is forcibly displaced relative to the other, the action is called faulting. ○ Types of Faults ● Normal Faults- results from tension stresses (pulling apart) in the crust. ● Reverse Faults- produced from compression stresses (pushing together) , where one block slides up the incline of the fault plane. ● Thrust faults- compression forces the upthrown block to override the downthrown block ar a relatively low angle, sometimes for many kilometers. ● Strike-slip faults- side to side movement with the adjacent blocks being displaced laterally relative to each other. ■ Fault Scarps- steep cliffs that represent the edge of a vertically displaced block ○ Landforms Associated with Normal Faulting ■ Fault Block Mountain- Sierra Nevada in California ■ Horst- a block of crust uplifted between two parallel faults ■ Rift Valleys-a large elongated depression with steep walls formed by the downward displacement of a block of the earth's surface between nearly parallel faults or fault systems. ○ Landforms Associated with Strike-Slip faulting Earthquakes ○ Seismic Waves ○ Earthquake Magnitudes ○ Shaking Intensity Earthquake Hazards ○ Ground Shaking ■ Liquefaction ■ Landslides ○ Tsunami ○ Earthquake hazard Warnings ■ Earthquake Early Warning Systems Complexities of the Internal Processes---- example of the Northern Rockies...