Download Continental Drift Theory

Continental Drift & Plate Tectonics
Continental Drift Theory
• First proposed by Alfred Wegener in 1912:
– 250 million years ago, all of the continents
were combined into one super-continent
called “Pangaea”
– The continents gradually drifted apart to
where they are today
• Wegner didn’t make up this theory out of
the blue – like all scientists, he based it on
evidence
Evidence Summary
• Geographic fit of South America and Africa
• Fossils match across oceans
• Rock types and structures match across
oceans
Geographic Fit
• Continents look like
they could be part
of a giant jigsaw
puzzle
• Here’s how they
moved apart
Fossils Match
• Plant and animal fossils found on the coastlines
of different continents
Fossil Fuel in Antarctica
• Tropical plant remains (coal deposits) found in
Antarctica
– this is evidence that Antarctica was once much warmer
and much closer to the equator, since tropical plants
don’t grow in Antarctica today
Rock Structures Match Across Oceans
• Same rock patterns found in South America,
India, Africa, Antarctica and Australia
Rock Structures Match Across Oceans
Alfred Wegener
- German
meteorologist
and geophysicist
- Developed
Theory of
Continental Drift
- Used 3 pieces of
evidence
- Early 1900s
The theory that
states that parts
of Earth’s crust
drift/float on top
of the liquid
mantle
(convection
currents).
PANGAEA
-Gigantic superContinent that
existed over 200
million years ago.
-Means “ALL
EARTH”
Evidence
-Continents fit
together
Like puzzle pieces
-Same fossils were
Found where
pieces fit
Together
-Similar landforms
found
On each continent
North
America
Europe
Asia
Africa
South
America
Australia
Antarctica
8. Juan De Fuca
Eurasian
North American
Arabian
10. Cocos
Pacific
11. Caribbean
African
South American
Nazca
Scotia
Philipine
15. Caroline
Indo-australian
Antarctic
Convergent
“Colliding”
Divergent
“Dividing”
Transform
“Sliding”
- Forms mountains
- Indo-Australian
plate collides with
Eurasian plate to
form Himalayan
Mountains.
- On land, forms rift
valleys
- In ocean, forms sea
floor spreading
- “Mid-Atlantic Ridge”
- Causes
earthquakes
- San Andres Fault