Post on 14-Jun-2015
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Plate TectonicsAnn C. Cloutier
Pangaea Continental DriftSea Floor SpreadingIsochron Maps – Geomagnetic Core GPS Sonar
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Continental Drift from a Hypothesis by Alfred Wegener and was developed into a Theory with supporting evidence Super continent called Pangaea >Greek for “all
land”
Began to brake apart over 200 million years ago
Puzzle fit of South America and Africa
Collected evidence in rocks, fossils, and climatic data to support his hypothesis
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Evidence to collect to support hypothesis but, no means to explain how the continents were moved…yet !
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Glossopteris and Mesosaurus
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Ancient climatesevidence of coal deposits found in Antarctica coal is formed from swamp plant or other
vegetation that has decomposed
this meant a temperate rainy climate was once on the surface of Antarctica
glacial deposits of till and striation scratches on bedrock found in Afrrica, 290 million year old land formations
today Africa is covered by huge deserts where the evidence of continental glaciers was documented
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How is coal formed ?
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Today 290MYBP
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Seafloor Spreading
Technology sonar echo-location > sound beams / time returned
WWII submarine warfare developed technology to detect more than an enemy sub
Detailed maps and a safe way to navigate the bottom
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Seafloor spreading Harry Hess
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Mid Ocean Ridges & Trenches Ocean ridges are long
mountain ranges Continuous wrap
around planet Deepest and longest
mountain range on the planet
~46,000 miles long (~ 72km)
Mariana Trench 11 km deep
deepest trench in all oceans
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Continental Crust - Oceanic Crust Oldest age 3.8 BYBP Billions of years
before present Less dense than
oceanic crust Continental
mountains keep getting folded and faults break up crust
Young age ~ today’s lava >180 MYBP
Millions of years before present
More dense than continental crust
The further away from the ridge the thicker and older the oceanic crust becomes
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Earth quakes occur at plate boundaries
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Seismic information
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Richter Scale Earthquake magnitude of seismic wave data
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Safety for Earthquake
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Causes of Plate Movement Mantle convection are thought to be the driving mechanism
of plate tectonic movement (continental drift caused by seafloor spreading and
subduction) The transfer of heat, called thermal energy is the cause of
the movement of hot matter (magma) moving to cold matter; this is called convection
Warm matter move toward cold matter Cooler matter sinks because it is more dense “G force” gravity pulls it down into the mantle Ridge push and slab pull are the results of this process of
heat moving away from the radiation of the core out towards the crust
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Convection current of Earth’s mantle the bulldozer pushes plates around the planet surface
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Isochron Map maps with magnetic fields showing Earth’s polarity for magnetic north
A line graph defined by data for rocks of the same age;
With the same isotopic composition
Polarity event is recorded in rocks a period of no more than 100,000 years when Earth’s magnetic polarity was opposite to the existing polarity
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Check out and watch this movie on your iPad
http://science.discovery.com/tv-shows/greatest-discoveries/videos/100-greatest-discoveries-magnetic-field-reversal.htm
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http://www.youtube.com/watch?v=1sNL-XaBmBk
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http://mysciencebox.org/files/images/magnetic_reversal_animation.gif
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Questions? Going further time for the iPad technology Do scientist know if convection currents
stay in the same places ? Are hot spots located in the same places ? For how long ? Is Cape Cod located on a hot spot? What state is located over a hot spot ? When was the last earthquake Cape Cod
felt ?