Plate tectonics power point 2012 acloutier

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Plate TectonicsAnn C. Cloutier

Pangaea Continental DriftSea Floor SpreadingIsochron Maps – Geomagnetic Core GPS Sonar


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


Evidence to collect to support hypothesis but, no means to explain how the continents were moved…yet !


Glossopteris and Mesosaurus


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


How is coal formed ?


Today 290MYBP


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


Seafloor spreading Harry Hess


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


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


Earth quakes occur at plate boundaries


Seismic information


Richter Scale Earthquake magnitude of seismic wave data


Safety for Earthquake


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


Convection current of Earth’s mantle the bulldozer pushes plates around the planet surface


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


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


http://www.youtube.com/watch?v=1sNL-XaBmBk


http://mysciencebox.org/files/images/magnetic_reversal_animation.gif


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 ?

Plate tectonics power point 2012 acloutier

Technology

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