Plate Tectonics
Plate Tectonics The Continental Drift Hypothesis Plate Tectonics – Overview Divergent Boundaries Convergent Boundaries Transform Boundaries
The Continental Drift Hypothesis GEOL131: Plate Tectonics The Continental Drift Hypothesis
Alfred Wegener (1880-1930) German paleoclimatologist GEOL131: Plate Tectonics: Continental Drift Alfred Wegener (1880-1930) German paleoclimatologist Studied evidence for ancient climates Traveled extensively, collected thousands of samples Published continental drift ideas in 1915 Died during expedition to Greenland in 1930
Pangaea “All lands” 200 million years ago GEOL131: Plate Tectonics: Continental Drift Pangaea “All lands” 200 million years ago
Wegener’s Evidence The “continental jigsaw puzzle” GEOL131: Plate Tectonics: Continental Drift Wegener’s Evidence The “continental jigsaw puzzle” Trans-oceanic fossil matching Trans-oceanic rock matching Ancient climates
Wegener’s Evidence: Continental Jigsaw GEOL131: Plate Tectonics: Continental Drift Wegener’s Evidence: Continental Jigsaw
Wegener’s Evidence: Matching Fossils GEOL131: Plate Tectonics: Continental Drift Wegener’s Evidence: Matching Fossils
Wegener’s Evidence: Matching Rocks GEOL131: Plate Tectonics: Continental Drift Wegener’s Evidence: Matching Rocks Pangaea Present
Wegener’s Evidence: Ancient Climates GEOL131: Plate Tectonics: Continental Drift Wegener’s Evidence: Ancient Climates Pangaea Present
Reaction to Wegener’s Ideas GEOL131: Plate Tectonics: Continental Drift Reaction to Wegener’s Ideas Other scientists were highly critical Major problem: no good explanation for how continents could move Wegener proposed Moon’s gravity moved continents Continents pushed through ocean crust like icebreaker ships
Reaction to Wegener’s Ideas GEOL131: Plate Tectonics: Continental Drift Reaction to Wegener’s Ideas Moon’s gravity too weak Ocean crust too dense and strong Most scientists concluded continental drift was incorrect
Plate Tectonics: Overview GEOL131: Plate Tectonics Plate Tectonics: Overview
Earth’s Layers: Two schemes GEOL131: Plate Tectonics: Plate Tectonics Overview Earth’s Layers: Two schemes Based on composition Crust, mantle, core Based on seismic wave behavior Lithosphere, asthenosphere, mesosphere, outer core, inner core Lithosphere, asthenosphere most important for plate tectonics
Earth’s Layers: Two schemes GEOL131: Plate Tectonics: Plate Tectonics Overview Earth’s Layers: Two schemes Asthenosphere
Lithospheric Plates Rigid, brittle Continents are “embedded” in them GEOL131: Plate Tectonics: Plate Tectonics Overview Lithospheric Plates Rigid, brittle Continents are “embedded” in them
Why is plate tectonic theory successful? GEOL131: Plate Tectonics: Plate Tectonics Overview Why is plate tectonic theory successful? Provides plausible explanation for how continents move Doesn’t require them to “plow” through ocean crust
Two types of lithosphere GEOL131: Plate Tectonics: Plate Tectonics Overview Two types of lithosphere Oceanic Thin, dense, able to subduct into mantle “asphalt” Continental Thick, low density, buoyant, does not subduct “styrofoam”
GEOL131: Plate Tectonics: Plate Tectonics Overview Plate Motion
Plate Boundaries: Divergent GEOL131: Plate Tectonics Plate Boundaries: Divergent
Plates separate at divergent boundaries GEOL131: Plate Tectonics: Divergent Boundaries Plates separate at divergent boundaries New crust created by undersea volcanism
Seafloor eruption off coast of Oregon
Plate Boundaries: Convergent GEOL131: Plate Tectonics Plate Boundaries: Convergent
Plates come together at convergent boundaries GEOL131: Plate Tectonics: Convergent Boundaries Plates come together at convergent boundaries Three types, based on lithosphere involved Oceanic-oceanic Oceanic-continental Continental-continental
Oceanic-oceanic boundaries GEOL131: Plate Tectonics: Convergent Boundaries Oceanic-oceanic boundaries
Tsunami generation at subduction zones
Oceanic-continental boundaries GEOL131: Plate Tectonics: Convergent Boundaries Oceanic-continental boundaries
Continental-continental boundaries GEOL131: Plate Tectonics: Convergent Boundaries Continental-continental boundaries A.k.a. “continental collision zones” Example: India and Asia
Plate Boundaries: Transform GEOL131: Plate Tectonics Plate Boundaries: Transform
Plates slide past each other at transform boundaries GEOL131: Plate Tectonics: Transform Boundaries Plates slide past each other at transform boundaries
San Andreas Fault: A transform boundary GEOL131: Plate Tectonics: Transform Boundaries San Andreas Fault: A transform boundary Los Angeles is moving northwest San Francisco is moving southeast
San Andreas Fault: A transform boundary GEOL131: Plate Tectonics: Transform Boundaries San Andreas Fault: A transform boundary
GEOL131: Plate Tectonics End of Chapter