1. 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

2. 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?

3. 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??

5. 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?

6. 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

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

8. 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)

10. Mantle Convection At which boundary is this occurring?
Boundary: explains all three types!

11. The India terrane being added to the Eurasian continental plate, it is now part of the continent.

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