1. GEOLOGY Notes PART 1
Alfred Wegener (1912)
proposed that all the continents were once joined as a single landmass
called this “supercontinent” Pangaea
called his theory “Continental Drift”
stated the continents have separated and collided as they have moved over millions of years
Problem= could not explain WHY

2. Continental Drift

3. Wegener’s 5 major pieces of Evidence:
Continents (esp. South America & Africa) seem to fit together like pieces of a puzzle
Matching fossils occur on east coast of S. America & west coast of Africa
Matching folded mountain belts on coasts of S. America & Africa

4. Data for latitudes & longitudes of locations is changing
Evidence cont…
Evidence of ancient climates show landmasses were once located elsewhere
Ex: glaciers in Africa !
Data for latitudes & longitudes of locations is changing

5. Modern Theory = Plate Tectonics
The crust is made up of about a dozen major, moving plates and several smaller plates
Plates can contain:
land = continental crust
ocean = oceanic crust
Both !

6. Modern Evidence from the Oceans
Scientists mapping the ocean floor found:
Underwater mountain chains
Ridges where the sea floor was actually spreading at sites called ridges
Some oceans were growing wider from the middle
Fossils and other materials are moving apart on either side of ridges
Newer, younger crust was being created by magma at the ridges

7. Magnetic measurements of the crust
Modern Evidence cont…
Magnetic measurements of the crust
Polarity (magnetic north vs. south) changes every so many thousand years
Magnetic rocks on the ocean floor show reversals
Rocks are in equal bands on either side of the mid-ocean ridges

8. What Moves the Plates?
Convection currents are created as heated rock rises to the surface, cools, and sinks again.
These currents carry the plates as if they are on a
conveyor belt in
a process called
“slab pull.”