Section 8.1 pages 172- 175 Wegener’s Continental Drift Hypothesis Evidence: 1. So. America and Africa fit like “puzzle” pieces. 2. fossil reptile “mesosaurus” only found on S. America & Africa. 3.ancient rocks, minerals, mountains, glacial features 4. similar climate changes. 5. present day animal species have common ancestors (Darwin) Continents were once together and have moved / drifted apart to their current location over time. His hypothesis is was REJECTED. He couldn’t adequately explain HOW the continents had moved. Plate Tectonics Theory 1940’s WWII ships using sonar technology to map ocean floor Discovered mountains, ridges, trenches, Evidence: 1. newly discovered sea floor spreading with lava 2. ocean floor was young by ridge and old away 7 major Lithospheric PLATES were slowly moving (2-10 cm/yr.) Plate consist of continents AND ocean floor SEA-FLOOR SPREADING is occurring at mountain RIDGES

Describe a hypothesis that attempts to explain WHY , HOW, plates move. (pg. 180) Describe a hypothesis that attempts to explain WHY , HOW, plates move. What FORCE CAUSES the lithospheric plates to move?

Ridge push Slab pull Mantle convection How can you explain sea-floor spreading? What is the energy source that drives each model? Which explains both convergent and divergent boundaries? Which is the weakest and strongest of the models at explaining plate movement? Which uses the circulation of magma to explain plate movement??

Ridge Push Magma rises, (less dense) pushes up cools and solidifies it exerts a force on the surrounding rock pushing it apart. More of a gravitational sliding than a true ridge push Boundary: divergent At what BOUNDARY TYPE does this occur?

Slab Pull The force GRAVITY on the the sinking edge of an oceanic plate pulls the rest of the plate into the asthenosphere. Forms a trench. Boundary: convergent O-O O-C Ocean floor is dragged into the mantle, melted and destroyed

Asthenosphere (asthenos- weak) 100 km to 660 km upper mantle Soft, solid/liquid, weak in structure, constantly changing

Interaction between lithosphere and asthenosphere But the lithosphere sits “floats” on top of the asthenosphere. Lithosphere (land) gets moved (like a person being moved on an escalator)

Mantle Convection At which boundary is this occurring? Boundary: explains all three types! http://maggiesscienceconnection.weebly.com/mantle-convection-plate-tectonics-earthquakes--volcanoes.html http://earthguide.ucsd.edu/eoc/teachers/t_tectonics/p_convection2.html

The India terrane being added to the Eurasian continental plate, it is now part of the continent. http://www.youtube.com/watch?v=loFxYSHxTf0&feature=related

India is now attached (part of) the Eurasian continent making it larger Himalayan Mountains India