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Download Development of the Theory of Plate Tectonics
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Transcript
Name ________KEY_____________________________________ Date ____________________________ Development of the Theory of Plate Tectonics What is the hypothesis of continental drift? What is the evidence supporting continental drift? How was sea flooring spreading discovered? What was the theory of sea floor spreading? What is the evidence supporting sea floor spreading? What is the theory of plate tectonics? What forces drive the movement of the plates? In 1912 a meteorologist, Alfred Wegener described the Continental drift hypothesis. It states that the continents have moved slowly to their current locations originating from a landmass called Pangaea. • Puzzle-like fit of continents • Similar fossils found on different continents • Remains of warm-weather plants in Arctic areas and glacial deposits in tropical areas • Similar rock structures are found on different continents Using sound waves In the 1960s, Harry Hess used data collected to suggest the theory of seafloor spreading to explain the ridges. He explained that: 1. Hot, less dense material below Earth’s crust rises upward to the surface at the midocean ridges. 2. Then, it flows sideways, carrying the seafloor away from the ridge. • The youngest rocks are located at mid-ocean ridges, and the oldest sea floor is furthest from the ridge near continents. • Reversals of Earth’s magnetic field are recorded by rocks in strips parallel to ridges. The theory of plate tectonics states that the Earth's lithosphere is made up individual plates that are broken down into over a dozen large and small pieces of solid rock. • Mantle convection • Gravity • Earth’s Rotation What are the 3 types of plate boundaries? • Divergent • Convergent • Transform DIVERGENT BOUNDARIES Overview Divergent boundaries are where the plates move away from each other and new crust is created. Divergent boundaries can occur on land or in the ocean. Oceanic Overview Will cause… The rising convection current below the oceanic plate lifts the lithosphere producing a mid-ocean ridge. The lithosphere becomes stretched and fractured. The open fracture allows magma to flow into the fracture, solidify and repeat. Mid-ocean ridge Sketch Example Mid-Atlantic Ridge Continental Overview A pulling force on continental plates causes a fracture that creates a rift-shaped structure. Earthquakes occur as a result of this fracturing and movement. Will cause… Rift valley Sketch Example East Africa Rift Valley CONVERGENT BOUNDARIES Oceanic and Oceanic Overview Will cause… Convergent boundaries are where the plates collide with one another causing the subduction of one plate beneath the other. One plate will “ride” over the other; the other plate will go into a trench. • • Volcanic island arcs Deep sea trenches Sketch Example Aleutian Islands Continental and Continental Overview Both plates will crumple and deform. Will cause… High mountain ranges Sketch Example Himalayan Mountains Oceanic and Continental Overview The thinner, denser oceanic plate subducts under the thicker, lighter continental plate. Will cause… Volcanic mountains Sketch Example Andes Mountains Transform Boundaries Overview At transform boundaries no new crust is created and none is destroyed. Instead the plates slide horizontally past one another. Will cause… Earthquakes Sketch Example San Andreas Fault Graphic organizer Sketch the graphic organizer.
