Download Seafloor Spreading - explained how continents could move

Plate Tectonics Prof. Voss
Page 1
Continental Drift
match continent
shapes
fossils
rock types
image:
pangea pangea-r-anim
200 million years ago
single continent
Pangea
image:
cdrift cdrift-a
150 million years ago
Laurasia in north
Gondwana in south
image:
cdrift cdrift-b
image:
pangea pangea-anim
70 million years ago
current continents
different positions
image:
cdrift cdrift-c
image:
cdrift cdrift-d
Seafloor Spreading - explained how continents could move
ocean floor young compared to land
little sediment - igneous rock
Midocean Ridge
mountain range in center of oceans
molten rock from mantle
rises through crack
spreads outward and hardens
carries continents along
record of Earth's magnetic field
image:
midocean midocean-ridgeridge-mag
Plate Tectonics - movement of large sections of Earth's crust
plate
section of crust
tectonics
Greek for "builder"
image:
06 06-03
plates move because mantle is highly plastic just below surface
convection current rise from center, break crust
slide at rates of a few cm/yr
midocean rise and rift - where new crust is formed
subduction zone - old crust destroyed, deepest part of oceans
melts, lowlow-density magma rises, volcanos, mountains
image:
06 06-04
Continental
11/18/2001
Plate Tectonics Prof. Voss
Drift
continued
motion of
plates
Earthquakes
along plate
boundaries
Page 2
image:
platemove
image:
06 06-06
PLATE BOUNDARIES
A. Divergent
new crust created
plates move apart
midmid-Atlantic ridge
image:
plateboundaries
B. Convergent
plates pushed together
one plate pushed
back to mantle
high mountains
over continents
deep trenches
in oceans
C. Transform
or Transcurrent
plate slide laterally
past each other
San Andreas fault
image:
contcont
image:
oceanocean
image:
SAtransform
image:
PLateboundary
Erosion - Earth sculpting
removal of parts of crust
to new locations
Weathering reduces rocks
to loose debris
that can be moved
chemical
water, oxygen,
carbonic acid
forms new materials
mechanical
image:
erosion
image:
11/18/2001
Plate Tectonics Prof. Voss
water, waves, freezing
roots
mass-wasting
movement to lower ground
streams, hydraulic action
Page 3
bryce
11/18/2001