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
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.