Continental Drift Theory

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

Continental Drift Theory 5 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.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

• Inner Core • Outer Core • Mantle • Crust • Atmosphere http://library.thinkquest.org/04oct/01724/images/Earth-crust-cutaway-english.png

• 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

• 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

• 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.

• 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

• Rift Valley Divergent Boundary Continental 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

• 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 …?

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