Warm-up #43 Mar. 26

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Warm-up #43 Mar. 26. Brainstorming: Will California eventually slide into the ocean? Have continents really drifted apart over the centuries?. Unit 8. Plate Tectonics. Continental Drift. Alfred Wegener German scientist proposed the theory of continental drift. - PowerPoint PPT Presentation


<p>Plate Tectonics</p> <p>Warm-up #43 Mar. 26Brainstorming:Will California eventually slide into the ocean?Have continents really drifted apart over the centuries?Plate TectonicsUnit 8</p> <p>Continental DriftAlfred Wegener German scientist proposed the theory of continental drift.This hypothesis stated that the continents had once been joined to form a single supercontinentPangaea all land</p> <p>PangaeaPart of Wegeners theory was that Pangaea started splitting into smaller continents 200 million years beforeWegener collected lots of evidence to prove this theoryThe Continental PuzzleThe shorelines of the continents nearly fit together to make a large land mass.HOWEVERThe shorelines are constantly eroding and changing.</p> <p>Matching FossilsFossil evidence for continental drift includes several fossil organisms found on different landmasses.At one point the theory was that there were land bridges, however there is no evidence of this.</p> <p>Rock Types and StructuresSeveral mountain belts that end at one coastline reappear on a landmass across the oceanAncient ClimatesWegener found glacial deposits showing that between 220 million and 300 million years ago ice sheets covered large areas of the S. Hemisphere</p> <p>Rejecting Wegeners HypothesisMany scientists questioned Wegeners theoryHe could not describe a mechanism that was capable of moving the continentsThere was not enough evidenceA New TheoryIn 1968 a new theory was proposed </p> <p>PLATE TECTONICS</p> <p>PlatesThe lithosphere is broken up into segments called platesThe lithosphere is the uppermost layer of the mantlePlates continuously move and change shape and sizeWarm-up #44 Mar. 27Mesosaurus provided evidence that South America and Africa were once joined</p> <p>On average, how much do you think the plates move a year? 5 centimeters</p> <p>Plate BoundariesA plate boundary is where two plates meet.There are three main types of boundaries:DivergentConvergentTransform faultDivergentAlso called spreading boundariesOccurs when two plates move apartResults in upwelling of material from the mantle to create new seafloor</p> <p>Convergent Form where two plates move togetherResults in lithosphere plunging beneath an overriding plate and descending into the mantle</p> <p>Transform faultMargins where two plates grind past each other without the production or destruction of lithosphere</p> <p>What happens at boundaries?Divergent BoundariesSeafloor spreading occurs along the boundaryForms fractures on the ridge crestsFractures fill with molten materialWhen the boundary occurs on a continent, rifts or rift valleys formConvergent BoundariesOceanic-continental boundaryForms a subduction zone withinVolcanic arcs formOceanic-oceanic boundaryOften forms volcanoes on the ocean floorIsland arc forms as volcanoes emerge</p> <p>Convergent BoundariesContinental-continental boundariesNeither plate will subductCan produce mountains</p> <p>Transform Fault BoundariesNo new crust createdNo crust is destroyedMost are in oceanic crustParallel the direction of plate movementAids movement of crustal material</p> <p>Boundary BrochuresNeeds to include:3 types: Divergent, Convergent, TransformWhat each one is (use your notes)A picture for eachAn example for eachhttp://geology.com/plate-tectonics.shtmlNeeds to be colored</p> <p>Warm-up #45 Mar.28Brainstorming:Do you think it is possible for Earths magnetic poles to be reversed?If so, what do you think could happen to the biosphere?Also, how might geologist use that to support plate tectonics?Evidence for Plate TectonicsPaleomagnetismMost persuasive piece of evidence.Ancient magnetism preserved rocks.Paleomagnetic records show:Polar wanderingEarths magnetic field reversals</p> <p>Strongest evidence of seafloor spreading24Evidence for Plate TectonicsEarthquake patternsAssociated with plate boundariesDeep-focus earthquakes along trenches provide a method for tracking the plates descent</p> <p>Evidence for Plate TectonicsOcean DrillingDeep Sea Drilling Project Glomar ChallengerAge of deepest sedimentYoungest are near the ridgesOlder are at a distance from the ridgeOcean basins are geologically young</p> <p>Evidence for Plate TectonicsHot SpotsRising plumes of mantle material.Volcanoes can form over</p> <p>Driving MechanismNo one model explains all plate motionEarths heat is the driving force Several models have been proposedConvection currents in the mantleSlab-pull and slab-push model Hot plumesDynamic Earthhttp://www.learner.org/interactives/dynamicearth/index.html</p> <p>Ticket out the DoorWhat are the 3 main types of plate boundaries?Name 2 pieces of evidence Wegener used to prove continental drift.What is type of boundary is this?</p>


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