Transcript Plate Tectonics

11/12/15
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Pieces of lithosphere
that move around on
top of asthenosphere
Act like pieces of a
jigsaw puzzle that fit
together to form
lithosphere
Not all tectonic plates
are the same
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Differences in size and
shape
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North American plate
versus Cocos plate
Parts of crust they
contain:
Cocos and Nazca plates:
only oceanic crust
 North plate: continental
and oceanic crust
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Continental drift:
theory that continents
can drift apart
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Proposed by Alfred
Wegener
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Originally rejected
because of lack of
evidence
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Fossil findings
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Mesosaurus (reptile)
Glossopteris (plant)
 Found on four different
continents
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Glacier activity
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Grooves created over
time match up when
continents once fit
together
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Pangaea: “all earth”
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Began over 225-245
million years ago
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Panthalassa: “all sea”
Both Greek terms
Laurasia
Gondwana
65 million years ago
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Further breakup
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Process by which new
oceanic lithosphere is
created
Occurs at mid-ocean ridges
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Mid-Atlantic Ridge
Underwater mountain
chains that run through
Earth’s ocean basins
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Sea floor spreads as
tectonic plates spread
apart
Magma rises to fill gap
newly created gap
Newest crust is found
along ocean ridges
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Oldest found near
edges of continents
New lithosphere
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Process in which Earth’s magnetic poles
change place
Provides evidence of sea-floor spreading
Molten rock contains tiny grains of magnetic
minerals (act like compasses)
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Once molten rock cools minerals are “set in stone”
Magnetic fields reverse each time a new band starts