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Lecture Five: Plate Tectonic - Coggle Diagram
Lecture Five: Plate Tectonic
ideas
Hoosier Frank Taylor
Atlantic was where Africa and South Amer. were joined, when continents collided it produced mountains
Eduard Suess
constant fossils of fern (Glossopteris) found many countries
connected by land bridges that sank beneath oceans- supercontinent (Gondwanaland)
Alfred Wegener
continental "fit" --> all conts. once together (Pangae)
Evidence:
similar rock types across conts.
"Gondwana Sequence" across conts.
Mesozoic basaltic lava flows, sedimentary rocks with Glossopteris and coal, late Paleozoic glacial tillites
Glacial striations across conts.
in notes
Mid-Ocean ridges
Sea-floor spreading
new oceanic lithosphere is created along undersea mountain chains
no oceanic crust found after 200 million years
in notes
Trenches
Magnetic _
Paleomagnetism
earth has magnetic field some rocks preserve when they form
slide 21
Rocks (same age, from same cont.) typically have all same paleomagnetic signature
these rocks often record a diff latitude than today and points towards poles in diff locations over time
either the poles moved or the conts. moved
over periods of 10,000 years the magnetic pole directly correlates with rotational pole
Earth's magnetic field acts like a giant bar magnet
inclination of magnetic field is 90 degrees at poles, 0 degrees at the equator, changes everywhere else
gives latitude
Magnetic declination: difference between magnetic north pole and the rotational north pole
varies over position on the earth
varies over time as magnetic pole moves
Apparent Polar Wandering
if magnetic poles wandered over time the polar wandering path would be the same for all conts. BUT polar wander curves are significantly diff for each cont. --> conts. must move
mechanism behind plate tectonics
convection
push and pull plates around
continental drift + seafloor spreading + trenches = plate tectonics