Plate Tectonics Video 100 greatest discoveries Magnetic Reversals

Plate Tectonics Video 100 greatest discoveries Magnetic Reversals Plate tectonic minute Earth

Harry Hess • Harry Hess: in the 1950’s Mapped the sea floor • Discovered that: The sea floor was not flat and that the Seafloor is spreading

Seafloor Spreading • Rock is youngest near the mid-ocean ridge- where the plates are spreading apart • As you get further away from the mid-ocean ridge rock gets older

Subduction Zones • Subduction zone: an area where the seafloor is getting recycled into Earth’s mantle • Seafloor spreading was the key to the Continental Drift theory • Showed us HOW the plates could move

Paleomagnetism • The Earth’s magnetic field has reversed several times in Earth’s past • Magnetic striping of the seafloor: Magnetite on the seafloor records the reversals when the rock solidifies

Adding to Wegener’s Theory • In 1960 the new evidences led scientists to revive Alfred’s theory 1. Seafloor spreading 2. Subduction zones 3. Age of the seafloor 4. Paleomagnetism

Theory of Plate Tectonics • Theory of Plate Tectonics: Earth’s crust is broken into plates that move around on the mantle

Convection Currents • Convection currents move the plates a few centimeters a year

Plate Boundaries • Divergent boundaries: plates move apart • Spreading zone, zone of divergence • Convergent boundaries: plate move toward each other • Subduction zone, zone of convergence • Transform boundaries: plates move side-by-side • Fault line

7 Major Plates • North American • South American • African • Pacific • Eurasian • Antarctic • Australian