continental drift theory alfred wegener german meteorologist found papers describing similar fossils...
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Continental Drift Theory
• Alfred Wegener• German meteorologist
• Found papers describing similar fossils on opposite sides of the Atlantic
• Researched more cases of similar organisms separated by oceans
• 1912 Proposed single supercontinent Pangaea
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.GIF
Wegener’s 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_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=SCE304Click animation
Volcanic rocks on the seafloor have magnetization because, as they cool,
magnetic minerals within the rock align to the Earth’s magnetic field.
New Evidence: Magnetic pattern of rock
North Magnetic Pole in No. Hemi
North Magnetic Pole in So. Hemi
Present DayNorth 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 Theory
Plates ‘float’ on the AsthenospherePlates have oceanic and continental crust
www.wiley.com/college/herenow/ptect/pt-map1.gif
Earth’s 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/Earth-crust-cutaway-english.png
Continental Crust
• Cooling rate - slow• Crystal size - large• Density – less dense• Thickest portion of the Earth’s outer layer• Composition – made mainly of granite rock
http://www.amonline.net.au/geoscience/images/earth_diagrams/cont_oceanic_crust.gif
Oceanic Crust
• 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%20Blog%20Resources/Images/Plate%20Tectonics/Plate%20Tectonics/VolcanoStructure.jpg
Earthquake - result of sudden energy release in the Earth’s crust creating seismic waves.
• 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 TYPESCLICK http://www.pbs.org/wgbh/aso/tryit/tectonics/shockwave.html
Andes MountainsConvergent Oceanic & Continental
Plates move toward each other
blue.utb.edu/paullgj/images/Conv_Cont_Ocean.JPG
CLICK http://www.pbs.org/wgbh/aso/tryit/tectonics/convergent.html
A trench, a steep walled valley on the sea floor, forms here.
Denser oceanic crust subducts under less dense continental crust
Convergent BoundaryOceanic & Continental
CLICK http://geology.com/nsta/convergent-boundary-oceanic-continental.gif
Japan or Aleutian IslandsConvergent Oceanic & Oceanic
ceeps.colostate-pueblo.edu/.../smM1P1Fig15.gif
Denser oceanic crust subducts under less dense oceanic crust
Convergent BoundaryOceanic & Oceanic
http://geology.com/nsta/convergent-boundary-oceanic-oceanic.gif
HimalayasConvergent Continental & Continental:
http://www.pbs.org/wgbh/aso/tryit/tectonics/crush.html
Faulting and Folding
Convergent BoundaryContinental & Continental
http://geology.com/nsta/convergent-boundary.gif
Mid Atlantic RidgeDivergent Oceanic
At a divergent boundary lithosphere plates move away from each other
Divergent BoundaryOceanic
• Mid-Ocean Ridges – a structure formed from seafloor spreading.
CLICK http://geology.com/nsta/divergent-boundary-oceanic.gif
East African Rift ValleyDivergent Continental
Rift Valley – Pulling apart of crust due to tensional forces
ceeps.colostate-pueblo.edu/.../smM1P1Fig15.gif
Divergent BoundaryContinental
• Rift Valley
http://geology.com/nsta/divergent-boundary-continental.gif
San Andreas FaultTransform Plate Boundary
Plates slide past each other
www.wiley.com/college/herenow/ptect/pt-map1.gif
Transform Boundary
TRANSFORM SIMUALTIONSCLICK http://geology.com/nsta/transform-boundary.gifCLICK 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 Spots
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 continentalplates 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
• Radioactive element decay
• Core heat from layers pressure
• Convection currents
• Volcanoes
• Hot Springs
• Earthquakes
Evidence for Plate Tectonics
• Continents fit together• Fossil distribution• Common rock formations: same age• Glacier evidence: deposits, striations, scraping• Climate distribution
New evidence • Magnetic pattern of rock• Location of earthquakes and volcanoes • Location of mountain ridges, rift valleys,
mid-ocean ridges, and trenches
First evidence used for Continental Drift Theory