Download Plate Tectonics - Londonderry School District

Continental Drift Theory
• Alfred Wegener
• German meteorologist
• 1912 Proposed single
supercontinent Pangaea
• Continental Drift Theory
Continental Drift Theory
5 Types of Evidence
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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.GIF
Wegener’s Continental Drift Evidence:
• Continents ‘fit’
together in a single
land mass 250 mya
• CLICK Simulations
http://www.ucmp.berkel
ey.edu/geology/anim1.
html
http://www.eoearth.org/upload/thumb/f/fb/Plate_tectonics_over_time.gif/400px-Plate_tectonics_over_time.gif
Wegener’s Continental Drift Evidence : Plant and
animal fossils of the same species were found on
several different continents.
Wegener’s Continental Drift Evidence:
Similar sequence of rock or
rock formations have the same age
Wegener’s Continental Drift Evidence:
Glacial deposits, striations,
and scraping patterns
Wegener’s 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.
Wegener’s Theory Problems
1) 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.
2) Continents are not moving apart at the
speed Wegener proposed.
Wegener = 250cm/yr
Actual = 2 cm/yr
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.
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?objID=SCE304
Click animation
New Evidence - Magnetic pattern of rock
Volcanic rocks on the seafloor have
magnetization because, as they cool,
magnetic minerals within the rock align to
the Earth’s magnetic field.
North Magnetic Pole in No. Hemi
North Magnetic Pole in So. Hemi
Present Day
North Magnetic Pole in No. Hemi
Sea-Floor Spreading Hypothesis
by Hess & Deitz
CLICK Animation:
http://www.uwsp.edu/geo/faculty/ritter/glossary/s_u/sea_flr_spread.html
Plate Tectonics
www.wiley.com/college/herenow/ptect/pt-map1.gif
Plates ‘float’ on the Asthenosphere
Plates have oceanic and continental crust
Earth’s Layers
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http://library.thinkquest.org/04oct/01724/images/Earth-crust-cutaway-english.png
Inner Core
Outer Core
Mantle
Crust
Atmosphere
• Lithosphere – crust and
upper mantle, plates
move independently
• Asthenosphere-region
below the Lithosphere
Continental Crust
http://www.amonline.net.au/geoscience/images/earth_diagrams/cont_oceanic_crust.gif
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Cooling rate - slow
Crystal size - large
Density - less dense
Thickest portion of the Earth’s outer layer
Composition – made mainly of granite rock
Oceanic Crust
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Cooling rate - fast
Crystal size - small
Density – more dense
Thinnest portion of the Earth’s outer layer
Composition – Made mainly of basalt rock
http://faculty.weber.edu/bdattilo/parks/plume_ocean.jpg
Volcano- opening or rupture in the Earth’s
crust that allows molten rock to escape
http://cgz.e2bn.net/e2bn/leas/c99/schools/cgz/accounts/staff/rchambers/GeoBytes%20GCSE%20Bl
og%20Resources/Images/Plate%20Tectonics/Plate%20Tectonics/VolcanoStructure.jpg
Earthquake- result of sudden energy release in
the Earth’s crust creating seismic waves.
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http://news.bbc.co.uk/nol/shared/spl/hi/world/04/earthquake/img/earthquake.gif
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_boundaries.png
SIMULATIONS ON ALL BOUNDARY TYPES
CLICK http://www.pbs.org/wgbh/aso/tryit/tectonics/shockwave.html
Andes Mountains
Convergent Oceanic & Continental
Plates 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/tectonics/convergent.html
Convergent Boundary
Oceanic & Continental
CLICK http://geology.com/nsta/convergent-boundary-oceanic-continental.gif
Japan or Aleutian Islands
Convergent Oceanic & Oceanic
Denser oceanic crust subducts under less dense oceanic crust
ceeps.colostate-pueblo.edu/.../smM1P1Fig15.gif
Convergent Boundary
Oceanic & Oceanic
http://geology.com/nsta/convergent-boundary-oceanic-oceanic.gif
Himalayas
Convergent Continental & Continental:
Faulting and Folding
http://www.pbs.org/wgbh/aso/tryit/tectonics/crush.html
Convergent Boundary
Continental & Continental
http://geology.com/nsta/convergent-boundary.gif
Mid Atlantic Ridge
Divergent Oceanic
At a divergent boundary lithosphere plates move away from each other
Divergent Boundary
Oceanic
• Mid-Ocean Ridges – a structure formed from
seafloor spreading.
CLICK http://geology.com/nsta/divergent-boundary-oceanic.gif
East African Rift Valley
Divergent Continental
Rift Valley – Pulling apart of crust due to tensional forces
ceeps.colostate-pueblo.edu/.../smM1P1Fig15.gif
Divergent Boundary
Continental
• Rift Valley
http://geology.com/nsta/divergent-boundary-continental.gif
San Andreas Fault
Transform Plate Boundary
Plates slide past or
laterally along each other
www.wiley.com/college/herenow/ptect/pt-map1.gif
Transform Boundary
TRANSFORM SIMUALTIONS
CLICK http://geology.com/nsta/transform-boundary.gif
CLICK http://www.pbs.org/wgbh/aso/tryit/tectonics/transform.htm
http://vulcan.wr.usgs.gov/Imgs/Gif/PlateTectonics/Maps/map_plate_tectonics_world.gif
Evidence - Location of earthquakes and volcanoes
Hot Spot
• Volcanoes
that are found
in the center
of plates
(not on plate
boundaries)
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
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.
Location of Hot Spots
Hot spots result from hot, narrow plumes of
material that rise deep within the mantle.
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.
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
Internal Energy for Earth
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Radioactive element decay
Core heat from layers pressure
Convection currents
Volcanoes
Hot Springs
Earthquakes
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
Review: What is …?
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Hot Spot
Rift Valley
Trench
Subduction
Convection Current
Sea Floor Spreading
Mid Ocean Ridge
Convergent, Divergent or Transform Boundary