Let’s Review!
a. transfer of heat through liquids and
gases
= convection
b. transfer of heat by physical contact
= conduction
c. transfer of heat through waves
= radiation
A. Continental drift theory
. Alfred Wegener- German
Scientist, Wegener purposed
that all continents were once
joined together in a single
landmass & then have slowly
drifted apart.
He called his super continent
…Pangea
a. Theory is called: Continental Drift
b. 1st formed Pangaea “super continent”
The Evidence….
1.
2.
He first noticed that
the continents
seem to fit together.
Look at the fit of
South America’s
east coast and
South Africa's west
coast.
More Evidence.
1.
Similar landforms
a. Mountain ranges of S. America &
Africa line-up
b. coal fields of N. America & Europe
line up
More Evidence
. Fossils- similar fossils found where
landforms match. I.E Mesosaurus
.Another piece of evidence
Continent’s climates have change when
the land drifted. What are some clues
one might find of past climate?
Lots of evidence that
supports CD but did people
believe him?

http://science.discovery.com/videos/100greatest-discoveries-shorts-continentaldrift.html
Wegener’s hypothesis was rejectedcouldn’t explain why the continents
move. The answer we now know
= Convection currents caused by our core.
Convection box demo
Science Exercise: Answer the following questions….
Is there other evidences?
YES!
http://www.youtube.com/
watch?v=6CsTTmvX6mc
Modern day Evidences.
C. Sea-floor Spreading
1.
Mid-ocean ridges (MOR)- sea floor
spreads & new ocean floor creates
underwater mountain chains
East Pacific Rise & Others
Magnetic polarity
Polar
Reversals
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Late 1950’s began mapping the
ocean bottoms
Sonar, gravity and magnetics
Magnetic data showed odd
phenomenon
Appeared to be striped
Polarity reversal were identical on
each side of oceanic ridge
1960, Harry Hess proposes seafloor spreading
Confirmed by mini-Submarine
Alvin in 1960’s
Reversed magnetism seen in
Rocks.
Final Proof… The age of the
ocean bottom.
1968 United State Geologic Survey
(USGS)
 Deep sea drilling w/ Glomar Challenger
 Drilling showed the age correlation in
ocean floor rocks.
 Where do you think the oldest rocks are
located on the sea floor? Youngest?
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What's happening at the
other end of the sea floor
spreading centers????
3. Subduction- process of the ocean floor
sinking back into mantle
a. Deep-ocean trenches- deep water
canyons in ocean
Sea-floor Spreading
MOR-New
ocean crust
Subduction
Melting
Asthenosphere