2.07
Plate Tectonics – The Lecture Notes
1) Earth’s ___________________________________________________
a) Divided into large and small crustal plates
b) Makes up the ocean floor and the continental land masses, along with the upper mantle.
c) The oceanic crust averages 8 km deep but is dense enough to support the continental crust
riding on it. The continental crust averages 35 km deep – both are relatively thin.
d) The crust covers a thick molten, moving mantle (68% of the earth’s volume) and a heavy core,
composed of nickel and iron. The plate move in different directions resulting in the cracking of
the crust.
e) Major plate boundaries can be mapped using seismic activity.
2) The Major Plates:
a) __________________________________ b) ___________________________________
b) __________________________________ d) ___________________________________
e) __________________________________ f) ___________________________________
f) __________________________________ h) ___________________________________
i) __________________________________ j) ___________________________________
k) __________________________________ l) ___________________________________
3) Plate Boundaries: What happens when plates meet?
a) Oceanic to Oceanic boundary – ______________________________________
i) Both plates are composed of basalt, also Mg, Fe, and Si
ii) Both are made of high density rock
iii) The result is a vent, mid-ocean ridge is and example.
b) Continental to Continental boundary - ______________________________________
i) Both plates are granite, also Si and AL
ii) Plates have low density rock
iii) The result is that edges are forced up into mountains.
c) Oceanic to Continental boundary
_________________________________________________________________________
i) Lighter continental plate edge override the denser oceanic plate
ii) Oceanic plate edge are subducted down into the asthenosphere and are re-melted
iii) The result - Trenches
d) The Three Boundaries
2.07
The Theory of Plate Tectonics
4) 1912, _______________________________________ proposed the idea of a super-continent
called Pangea that broke apart to form today’s land masses
a) The Reasons
i) The continent’s shape roughly fit together
ii) The rocks and fossils of different continents matched
5) Harry Hess and J Wilson propose a mechanism to explain continental movement in the early 60’s.
to avoid critism the termed it “____________________________________________”
6) In 1969 the __________________________________________ drilled a series of holes in the
Mid-Atlantic ridge. What they found changed geology and oceanography.
a) Continental Rocks date the Earth at about 5 billion years old. Since the ocean floor is lower in
the lithosphere, scientists expected to find older
rocks at those depths.
Continental geology’s law of Superposition
states that oldest rocks are laid down first and
should be found horizontally lowest in a bed
unless uplifted.
b) They found no rock older than 3 billion years
and most were younger. How could the ocean
floor be younger than the continents riding on
it?
c) The Deep Sea Drilling project showed that
rocks became older as they moved away from
the mid ocean ridge.
d) Oceanic geology showed rock layers are created
vertically. The MOR seemed to be a parallel
distance from continents on either side.
e) Core samples revealed matching striping in
rocks on both sides of the MOR.
7) In 1977, ________________________________
photographed magma squeezing out of the MOR
and creating new ocean floor.
8) Scientists, ____________________________ had
data for a cohesive theory on plate tectonics. The
sea floor was spreading – moving continents with
it. The theory of sea floor spreading explained
continental drift. Proving Wegener to be correct.