Ch.4 Notes

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Ch.4Notes

• Plate Tectonics

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Continental Drift

• 400 years ago
• Magellan and Columbus mapping info
• Similar shoreline
• 1912 Alfred Wegener hypothesized
• Pangaea 1 land mass
• Panthalassa all seas

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World Map
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Evidence of Continental Drift

• Coastlines
• Fossils
• Mesosaurus lived 270 million years ago
• They cannot swim well
• Age and type of rocks Brazil Africa
• Mountain ranges
• Coal deposits
• Continents joined over South Pole
• No force making this happen?
• Still not accepted 1930s

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Continental Drift
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Sea floor spreading

• 1947
• Out of a ridge in the ocean floor magma flows
  creating new crust.
• Pushing old crust outward.
• Harry Hess Princeton, MidAtlantic Ridge
• Arthur Holmes hypothesis in 1930 to put Wegener
  hypothesis back on map

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Sea floor spreading
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Sea Floor Spreading
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Mid-Ocean Ridges

• Go around the earth
• 80,000 km long
• Undersea mountain range with a valley in the
  middle.

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Mid Atlantic Ridge
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Iceland
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Paleomagnetism of the ocean floor

• Magma has iron in it.
• Iron aligns with the poles like a magnet
• Reverse polarity in layers 1965

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Paleomagnetism of the ocean floor
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1960

• Hypothesis of continental drift and seafloor
  spreading turned into a theory.

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Assignment

• Pg. 71 Questions 1-4

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• Assigned
• Due
• Explain how Sea Floor spreading occurs.
• You must include
• - rift valley
• - magma
• - asthenosphere
• iron
• magnetism
• north and south poles
• use a diagram to help explain
• where the old rock and new rock is located
• why is this important to Alfred Wegeners idea of
  continental drift
• It should take at least 2 paragraphs to explain
  it in detail.

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The theory of Plate Tectonics

• Explanation of how and why the continents broke
  apart.
• Construction tectonics
• Crust
• 1. oceanic
• 2 continental
• Lithosphere upper mantle
• Asthenosphere solid rock that is under pressure
• 30 different plates

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Plate Tectonics
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Lithospheric Plate Boundaries

• Boundaries can be anywhere
• Divergent moving away
• Convergent moving toward
• Transform Boundaries moving across

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Divergent moving away

• Plates moving away from each other
• Asthenosphere flows upward to fill in
• Mid-ocean ridge
• Rift valley center of plate boundary
• Red sea is one

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Sea floor spreading
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Convergent moving toward

• Opposite side of divergent
• 1. Oceanic crust vs continental crust oceanic is
  denser so subduction goes under, continental
  crust goes up
• Forms deep ocean trenches
• Often forms volcanoes on land
• 2. If continental crust plates are even both
  crumple and go up (Himalayas)
• 3. oceanic and oceanic crusts one is subducted
• Deep trench and island arc of volcanoes

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Transform Boundaries moving across

• 2 plates grinding past each other
• Not smooth so many spurts
• San Andreas Fault in California

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Causes of Plate Motion

• Movement of lithospheric plates by convection
  (transfer of heat)
• Convectional current boiling rice
• Arthur Holmes

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Microplate Terranes

• Theory of plate tectonics refines continental
  drift theory
• Theory of microplate terranes
• Separate from other plates (neighbors)
• 1. Contains rock and fossils unique
• 2. major faults are the boundaries
• 3. magnetic properties differ
• Palo Alto fossils of coral reef
• Ocean floor sediments in California mountains
• Petosky stones

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Microplate Terranes
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Assignment

• Page 77
• Sec. 4.2 Questions 1-5
• Page 78-79
• Question 1-14

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