Presentation on theme: "Coach Williams Room 310B. Plate Tectonics Objectives Describe one piece of early evidence that led people to suggest the Earth’s continents my have."— Presentation transcript:
Coach Williams Room 310B
Objectives Describe one piece of early evidence that led people to suggest the Earth’s continents my have once been joined. Discuss evidence of continental drift Explain why continental drift was not accepted when it was first proposed.
Fit of continents across Atlantic Ocean Gondwanaland: southern continents
Theory that Earth’s continents were once joined. Continents had slowly drifted apart Pangaea: “all the Earth”
Rocks: similar rocks Fossils: animal/plant remains Ancient Climate: coal in Antarctica
2 Reasons the theory was rejected ◦ 1) What forces could cause them to move? ◦ 2) How could continents move and not shatter?
Objectives ◦ Summarize the evidence that led to the discovery of seafloor spreading. ◦ Explain the significance of magnetic patterns on the seafloor. ◦ Explain the process of seafloor spreading.
Sonar- sound waves to determine depth Magnetometer- detects changes in magnetic fields Map the ocean floor
Plates moving apart Most on ocean ridges Rift valley: narrow valley along divergent boundary
Plates moving together ◦ Oceanic crust – oceanic crust: volcanoes ◦ Oceanic crust – continental crust: volcanoes ◦ Continental crust – continental crust: mountains Subduction- one plate goes below the other
Plates slide horizontally
Objectives: Explain the process of convection Summarize how convection in the mantle is related to the movements of tectonic plates Compare/contrast the processes of ridge push and slab pull
Convection: movement due to temperature differences Mantle has convection currents Currents move plates Ridge push- weight of ridge pushes plate down Slab pull- weight of plate pulls plate down