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TAMU GEOL 101 - Geology 101 Class 2

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Geology 101-539Class 2-Test 1Thursday, September 4, 14Chapter 2: Plate Tectonics: The Unifying TheoryPart 1 of 2Outline- The discovery of plate tectonicso Continental drifto Seafloor spreadingo The great synthesis 1963-1968- Earth’s tectonic plateso Divergent boundarieso Convergent boundarieso Transform-fault boundariesContinental Drift- Large scale horizontal movements cause earth’s major topographical featureso Mountainso Oceans basins- Alfred Wegener (1880-1930)- Proposed in 1912 based on observation of drifting ice sheets- His analogy was used with icebergs floating on the water and drifting around- Geographic Fit Of The Continents…o One of the first pieces of evidence use to argue for continental drifto All continents were once together in a supercontinent called Pangea North America, South America, Africa, Europe example map- Fossil Match Across The Atlantico Paleontologists Animals and plants diverge in evolution after the postulated breakup time- Rejection and Acceptance of Continental Drifto Initially rejected by geologists Geologists said it is too good to be true New data after WWII led to 1960s plate tectonic revolution Ocean Drilling started happening Different data from magnetic, sonar, ocean drilling, etc, led to this revolution. (Earth Science Revolution)o Now fully embraced Textbooks re-writtenSeafloor Spreading- Convection in the Earth’s mantle could break up and push continents apart- Arthur Holmes (1890-1965)- He worked with the idea of convectiono Heat rises and cool sinks- Harry Hess (1906-1969)- He used the hypothesis of mantle convection to explain seafloor spreading, island arcs, gravity anomalies and serpentine rocks- He worked on a cruise ship and use that to his advantage to create and collect data- History of the ocean basins, 1962- He is the father of modern plate tectonics- Icelando An opening rift along the Mid-Atlantic ridgeo …new ocean crust forms at mid-ocean ridge- Earthquakes and Volcanoeso Their locations are predicted by plate tectonicso The Pacific “Ring of Fire” shows the volcanic and earthquake activity now know to be associated with convergence and destruction of lithospheric platesPlate Tectonics: The Great Synthesis- Plates comprises top of the mantle, oceanic crust, and or continental crust, called lithosphere **Could Be Test Question- Plates slide over partially molten, weak mantle region called asthenosphere- Plates are tens of km thick…- In relative motion w.r.t. each other driven by mantle convection- Lithospehereo Cold, outer rigid (brittle) shell of the Earth (100km) containing the plates. The coldest part- Asthenosphereo Heat-softened (viscous) part of the mantle beneath the lithosphere- …plate motion causes earthquakes and builds mountainsPlate Boundaries and Displacement Rates…- relative plate motions shown in mm/year- Number associated with arrow- What is the explanation for why the Pacific Plate is larger than the other plates?o Pacific Plate is the fastest moving/growing plate.The 3 Types of Plate Boundaries- Transformo At transform-fault boundaries plates slide horizontally past each other Ex: California- Divergento At divergent boundaries, plates move apart and create newlithosphere Ex: Iceland- Convergento At convergent boundaries, plates collide and one is pulled into the mantle and recycled Ex: Alaska- Transform Plate Boundaryo San Andreas Fault, runs along the coast of Californiao Ones that occur in the ocean floor, South American Plate/African Plateo Makes the rocks on either side different ages- Divergent Plate Boundaryo Volcanoes and earthquakes concentrateo Mid Atlantic Ridge-North American Plate/ African Plateo East African Rift Valley-African Plate/Somali Subplate Africa continent is breaking into opposite directionso Parallel valleys; volcanoes and earthquakes- Convergent Plate Boundarieso Ocean-continent …Continental arc volcanoes are formed Most common form of convergent plate boundarieso Peru-Chile trench-Nazca Plate/South American Plateo Andes Mountains-South American Plateo Ocean-Ocean  …Island arc volcanoes are formedo Japan Trench- Eurasian Plate/Pacific Plateo Japanese Islands (Island arc)- Eurasian Plateo Continent-Continent Fold and thrust mountains are formed, ex: HimalayasWhich of the locations listed below is least associated with a volcanically active plate boundary?a. mid-ocean ridgeb. deep ocean trenchc. transform fault-Quietest boundaryd. continental riftWhich kind of plate boundary is associated with earthquake activity?a. Divergent boundaryb. Convergent boundary c. Transform-fault boundaryd. All of the aboveAt which kind of plate boundary is new oceanic lithosphere formed?a. Oceanic transform boundaryb. Oceanic divergent boundaryc. Ocean- ocean convergent boundaryd. Ocean-continent convergent


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TAMU GEOL 101 - Geology 101 Class 2

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