Continental Drift
CH 9 Plate tectonics 1915 – Alfred Wegner proposed his continental drift hypothesis His hypothesis: 200 mya one large supercontinent Pangaea (all lands) began to break up Panthalassa – all oceans Not widely accepted b/c he couldn’t explain why the plate movement occurred
Continental Drift Evidence Wegner could not explain his hypothesis, but had evidence 4 Pieces of Evidence Continents fit like puzzle pieces Matching Fossils Ancient climate (glacial evidence) Rocks (matching mountain ranges)
Continents Fit Like Puzzle Pieces
Mesosaurus Fossils
Glacier Evidence
Rocks - Matching mountain chains
Breakup of Pangaea
Plate Tectonics
Plate Tectonics Move slowly about 5 cm or 2.5 inches per year (same as fingernails) Plate movement causes Earthquakes, volcanoes, mountains
Evidence for Plate Tectonics Paleomagnetism: rocks align with Earth’s changing magnetic poles showing patterns of spreading Ocean Drilling: seafloor sediments confirmed seafloor spreading Earthquake patterns: show plate boundaries Hot spots: show plate movement over magma plumes
Hot Spots
Hot Spots
What moves the plates? Convection Currents: the driving force behind plate tectonics.
What moves the plates? Convection Currents: the driving force behind plate tectonics.