Continental Drift Theory

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Continental Drift Theory

• Alfred Wegener
• German meteorologist
• 1912 Proposed single supercontinent Pangaea
• Continental Drift Theory

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Continental Drift Theory5 Types of Evidence

• Fit of the Continents
• Distribution of Fossils
• Sequence of Rocks
• Glacier Scraping Patterns
• Ancient Climates and Wandering Polar Regions

http//library.thinkquest.org/3669/media/map2dd.GI
F
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Wegeners Continental Drift Evidence

• Continents fit together in a single land mass
  250 mya
• CLICK Simulations
• http//www.ucmp.berkeley.edu/geology/anim1.html

http//www.eoearth.org/upload/thumb/f/fb/Plate_tec
tonics_over_time.gif/400px-Plate_tectonics_over_ti
me.gif
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Wegeners Continental Drift Evidence Plant
and animal fossils of the same species were found
on several different continents.
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Wegeners Continental Drift Evidence Similar
sequence of rock or rock formations have the
same age
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Wegeners Continental Drift Evidence Glacial
deposits, striations, and scraping patterns
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Wegeners Continental Drift Evidence Climate
distribution Past Present
Coal exists under the ice in the rock of
Antarctica yet coal can only form from plants
that grow in warm climates.
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Wegeners Theory Problems

• Wegener had no convincing mechanism (did not
  explain the forces) of how the continents might
  move. Continents plowing through the crust would
  destroy the crust.
• Continents are not moving apart at the speed
  Wegener proposed.
• Wegener 250cm/yr
• Actual 2 cm/yr

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Holmes Breakthrough Heat trapped in the Earth
caused Convection Currents in the mantle.

• As a substance is heated its density decreases
  and rises to the surface until it is cooled and
  sinks again.

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Convection currents

• Gravity causes the heated mantle to sink
• The mantle heats up near the core and then rises
  again
• Conduction is the transfer of heat between 2
  materials in direct contact with each other

library.thinkquest.org/C003124/images/convect.jpg
http//www.wisc-online.com/objects/index_tj.asp?ob
jIDSCE304 Click animation
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Volcanic rocks on the seafloor have
magnetization because, as they cool, magnetic
minerals within the rock align to the Earths
magnetic field.

New Evidence - Magnetic pattern of rock
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North Magnetic Pole in No. Hemi
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North Magnetic Pole in So. Hemi
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Present DayNorth Magnetic Pole in No. Hemi
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Sea-Floor Spreading Hypothesis by Hess Deitz
CLICK Animation http//www.uwsp.edu/geo/faculty/
ritter/glossary/s_u/sea_flr_spread.html
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Plate Tectonics
www.wiley.com/college/herenow/ptect/pt-map1.gif

• Plates float on the Asthenosphere
• Plates have oceanic and continental crust

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Earths Layers

• Inner Core
• Outer Core
• Mantle
• Crust
• Atmosphere
• Lithosphere crust and upper mantle, plates move
  independently
• Asthenosphere-region below the Lithosphere

http//library.thinkquest.org/04oct/01724/images/E
arth-crust-cutaway-english.png
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Continental Crust
http//www.amonline.net.au/geoscience/images/earth
_diagrams/cont_oceanic_crust.gif

• Cooling rate - slow
• Crystal size - large
• Density - less dense
• Thickest portion of the Earths outer layer
• Composition made mainly of granite rock

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Oceanic Crust

• Cooling rate - fast
• Crystal size - small
• Density more dense
• Thinnest portion of the Earths outer layer
• Composition Made mainly of basalt rock

http//faculty.weber.edu/bdattilo/parks/plume_ocea
n.jpg
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Volcano- opening or rupture in the Earths crust
that allows molten rock to escape
http//cgz.e2bn.net/e2bn/leas/c99/schools/cgz/acco
unts/staff/rchambers/GeoBytes20GCSE20Bl og20Res
ources/Images/Plate20Tectonics/Plate20Tectonics/
VolcanoStructure.jpg
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Earthquake- result of sudden energy release in
the Earths crust creating seismic waves.

• http//news.bbc.co.uk/nol/shared/spl/hi/world/04/e
  arthquake/img/earthquake.gif

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More Evidence- Location of mountain ridges,
rift valleys, mid-ocean ridges, and trenches on
plate boundaries. Convergent, Divergent and
Transform
http//www.ifa.hawaii.
edu/barnes/ast110_06/tprai/Tectonic_plate_boundar
ies.png
SIMULATIONS ON ALL BOUNDARY
TYPES CLICK http//www.pbs.org/wgbh/aso/tryit/tect
onics/shockwave.html
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Andes MountainsConvergent Oceanic
ContinentalPlates move toward each other
A trench is a steep walled valley on the sea
floor. Subduction - A convergent boundary where
one plate moves below the other plate
blue.utb.edu/paullgj/images/Conv_Cont_Ocean.JPG
CLICK http//www.pbs.org/wgbh/aso/tryit/tecton
ics/convergent.html
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Convergent BoundaryOceanic Continental
CLICK http//geology.com/nsta/convergent-boundary
-oceanic-continental.gif
http//geology.com/nsta/plate-tectonics-cover.gif
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Japan or Aleutian IslandsConvergent Oceanic
Oceanic
Denser oceanic crust subducts under less dense
oceanic crust
ceeps.colostate-pueblo.edu/.../smM1P1Fig15.gif
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Convergent BoundaryOceanic Oceanic
http//geology.com/nsta/convergent-boundary-ocean
ic-oceanic.gif
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HimalayasConvergent Continental Continental
Faulting and Folding

http//www.pbs.org/wgbh/aso/tryit/tectonics/crush.
html
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Convergent BoundaryContinental Continental
http//geology.com/nsta/convergent-boundary.gif
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Mid Atlantic RidgeDivergent Oceanic
At a divergent boundary lithosphere plates move
away from each other
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Divergent BoundaryOceanic

• Mid-Ocean Ridges a structure formed from
  seafloor spreading.

CLICK http//geology.com/nsta/divergent-boundary-o
ceanic.gif
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East African Rift ValleyDivergent
ContinentalRift Valley Pulling apart of crust
due to tensional forces
ceeps.colostate-pueblo.edu/.../smM1P1Fig15.gif
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Divergent BoundaryContinental

• Rift Valley

http//geology.com/nsta/divergent-boundary-contine
ntal.gif
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San Andreas FaultTransform Plate
BoundaryPlates slide past or laterally along
each other
www.wiley.com/college/herenow/ptect/pt-map1.gif
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Transform Boundary
TRANSFORM
SIMUALTIONS CLICK http//geology.com/nsta/transfor
m-boundary.gif CLICK http//www.pbs.org/wgbh/aso/t
ryit/tectonics/transform.htm
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http//vulcan.wr.usgs.gov/Imgs/Gif/PlateTectonics/
Maps/map_plate_tectonics_world.gif
Evidence - Location of earthquakes and volcanoes
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Hot Spot

• Volcanoes that are found in the center of plates
  (not on plate boundaries)

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The Hawaiian-Emperor volcanic chain is the
result of the drifting of the Pacific Plate over
a fixed hot spot.
http//geology.com/nsta/plate-tectonics-cover.gif
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The bend in the (Hawaiian Emperor) volcanic
chain is the result of a major change in the
direction of the movement of the Pacific Plate.
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Location of Hot Spots
Hot spots result from hot, narrow plumes of
material that rise deep within the mantle.
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Plate Movement in the future

• http//www.scotese.com/earth.htm

It is even possible to measure the speed of
continental plates extremely accurately, using
satellite technology.
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External Energy For Earth

• Sun Moon keeps air and sea in motion, shapes
  surface
• Sun warms atmosphere crust unevenly creating
  winds
• Winds drive ocean currents and water cycle
• Erosion from winds, rains, rivers, glaciers, and
  waves shape surface
• Weathering from winds and rains
• Sun Moon Gravitational Energy, produces tides
• Planetesimal collisions

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Internal Energy for Earth

• Radioactive element decay
• Core heat from layers pressure
• Convection currents
• Volcanoes
• Hot Springs
• Earthquakes

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Evidence for Plate Tectonics
First evidence used for Continental Drift Theory

• Continents fit together
• Fossil distribution
• Glacier evidence deposits, striations, scraping
• Climate distribution
• Common rock formations same age
• New evidence
• Magnetic pattern of rock
• Location of earthquakes and volcanoes
• Location of mountain ridges, rift valleys,
  mid-ocean ridges, and trenches

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Review What is ?

• Hot Spot
• Rift Valley
• Trench
• Subduction
• Convection Current
• Sea Floor Spreading
• Mid Ocean Ridge
• Convergent, Divergent or Transform Boundary