Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
The Theory of Plate Tectonics Canadian scientist, J. Tuzo Wilson noticed the continental crusts had cracks similar to oceanic crust Lithosphere is broken into sections called plates • Plate tectonicsgeologic theory stating that pieces of Earth’s lithosphere are in constant, slow motion, driven by convection currents in the mantle The theory of plate tectonics explains the formation, movement, & subduction of Earth’s plates • Plates meet at plate boundaries extending deep in the lithosphere • Faults- breaks in Earth’s crust where rocks slip past each other form along boundaries 3 Types of Plate Boundaries • Divergent • Convergent • Transform Transform Boundary • Crust is neither created nor destroyed • 2 plates slip past each other moving in opposite directions • Earthquakes occur frequently here Divergent Boundary • Place where 2 plates move apart • Most found along mid-ocean ridge where oceanic crust diverges Divergent boundaries also occur on land • Rift valleys form when continental crust diverges • Rift may eventually split a continent Convergent Boundary • Place where 2 plates come together, converge • Collisions may occur between 2 oceanic plates, 2 continental plates, or an oceanic & continental plate Oceanic-Oceanic Convergence • Oceanic crust becomes cooler & denser as it spreads away from the mid-ocean ridge • 2 oceanic crusts meet at a trench & the more dense plate subducts under the other plate & returns to the mantle • Oceanic convergence creates island arcs Oceanic-Continental Convergence • Oceanic crust, made of basalt, is denser than continental crust, made mostly of granite • Oceanic plate sinks beneath the continental crust Continental-Continental Convergence • Subduction does NOT occur when 2 pieces of continental crust collide • Neither plate is dense enough to sink • Crust is squeezed into mountain ranges Continent’s Slow Dance • Plates move at an extremely slow rate, 110 cm/year • North American & European plate are moving apart at about the same rate as your finger nails grow Tracking Tectonic Plate Motion • Scientists use data from a system of satellites called Global Positioning System (GPS) to measure the rate of motion of tectonic plates. Review what you know… • 1. Define plate tectonics. • 2. Describe the three boundaries of plate movement. • 3. How do scientists measure the rate of tectonic plate movement?