Earth’s Internal StructureMantleAsthenosphereCrustContinental and Oceanic CrustsContinental DriftEvidence of PangaeaMid-Oceanic RidgesTheory of Plate TectonicsMovement of PlatesGEO 155 1st Edition Lecture 24Last Lecture Erosion on SlopesOutline of Current LectureI. Earth’s Internal StructureII. Continental vs. Oceanic CrustIII. Plate Tectonicsa. Major Platei. Boundariesb. Interaction of Plate Boundariesi. Divergenceii. Convergenceiii. TransformCurrent LectureEarth’s Internal Structure- Less know than atmosphere- Most pressure concentrated in inner core of earth (solid)- Liquid outer coreMantleLess dense than outer coreThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.1. Lower mantle – solid, thick, little movement2. Upper mantle – highly viscous, strong interaction with crusta. Low part below asthenosphere is mostly solid and plastic-likeb. Upper part is rigid like crust (asthenosphere)c. Lithosphere is above asthenosphere below the crustAsthenosphere- Rock is plastic-like and flows readily with pressure- Tectonic plates “float” on topCrust- Less dense than upper mantle- Separated from mantle by Mohorovicic (Moho) discontinuityo Thickness not consistent Moho closer under ocean floor Moho deeper for continental land massesContinental and Oceanic Crusts- Bottom ocean rocks are darker and denser, “Mafic rock”- Continental rocks have lowest density, “Felsic rock”Continental Drift- Francis Bacon noticed coasts of South America and Africa fit together like a puzzle- Alfred Wegener noted that all landmasses were united in a giant supercontinent during Paleozoic andMesozoic eras (Pangaea)- Continental drift is the slow movement of continents away from PangaeaEvidence of Pangaea - Fossil records are similar on different continents suggesting they were all once connectedMid-Oceanic Ridges- Mostly submarine mountain rangeso Example: Mid-Atlantic Ridge- Sea floor spreading along ridges – creation of a new lithospheric material and its continuous movement away from it sourceo Deep ocean basalt rocks much younger than continentalo Proves continental drift by movement of plate tectonicTheory of Plate Tectonics- Explain continental drift by movement of large lithospheric plates floating on asthenosphere- Explains formation, movement, and destruction of platesMovement of Plates - Plates move at velocities o 1-12 cm per year- Movement of plates directly responsible for many of Earth’s major topographic or bathymetric features- Landforms created depend on interaction of two plates by:1. Divergence – two plates move away from each other by tensional forces, crust thinned and broken by faultsa. Oceanic – example: ridgesb. Continental – rift valleys form, starts in continents but create oceansi. Example: East Africa Rift Valley and Red Sea formed when Arabian and African plates separated2. Convergence – two plates move toward each othera. Depends on type of lithospherei. If oceanic crust involved, subduction occurs and one of the crustal plates pushed below the other (denser)1. Subduction Zone – water carried by ocean plate forced down into overlying plate triggering melting of rocka. Some molten rock forced up through vents and fissures to surface – VOLCANISMb. Intense tectonic activity – EARTHQUAKES2. Oceanic-continental – subduction, continental rocks crumpled into mountain range often with volcanoes – e.g. Andes3. Oceanic-oceanic – subduction, deep ocean trenches and volcanic islandarcs e.g. Philippines4. Continental-continental – no subduction, produces massive mountain range3. Transform – two plates slide past each othera. Earthquakes and crustal deformation regularly occuri. E.g. San Andreas Fault – Pacific and North American Plate
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