CGC1D
Continental Drift and Plate Tectonics
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In 1912, German scientist ___________________________
proposed continents were once joined as a single continent
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Called this _____________________-meaning "all lands“
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Stated it ___________________________ into its current
position over time
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believed that Pangaea was intact until about
_______________________ years ago
Four Main Pieces of Evidence
1. ___________________________________________________
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2. ___________________________________________________
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3. ________________________________________
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4. _______________________________________
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PROBLEM:
_____________________________________________________________________________________
_____________________________________________________________________________________
….thus, the theory of ________________________________________!
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explained how the continents could separate in the 1960s
EARTH’S STRUCTURE
The Earth is made up of 3 main layers:
Core
Mantle
Crust
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THE CRUST
This is where we live! The Earth’s crust is made of:
 Continental Crust
thick (10-70km)
- buoyant (less dense than
oceanic crust)
- mostly old
Oceanic Crust
- thin (~7 km)
- dense (sinks under
continental crust)
- young
Why does this matter?
How do we know what the Earth is made of?
The __________________________________ make
up the lithosphere, which is what
____________________________ are made of.
Geophysical surveys: seismic, gravity, magnetics, electrical, geodesy
Acquisition: land, air, sea and satellite
Geological surveys: fieldwork, boreholes, mines
PLATE TECTONICS
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the theory states that outer surface of the Earth is a
__________________________________
______________________________, fractured like
the cracked shell of an egg
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Earth's _____ major tectonic plates float on top of
the asthenosphere (lower layer of the crust)
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Plates are moved around by the underlying hot
mantle ________________________________________
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Convection currents:
________________________________________________
________________________________________________
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Tectonics plates are
___________________________________ up to 2.5cm/yr!