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23 Cards in this Set
- Front
- Back
The Planet...
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is always changing shape. Mountains are forming. Oceans are getting wider and rocks "disapear"
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Layers of the Earth
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Lithosphere: thin, solid, outer layer
Mantle: plastic like layer, solid, 80% of earth Moho: boundry between mantle and crust Outer core: only liquid layer Inner Core: solid iron and nickle; 6000 degrees C |
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The Lithosphere (crust)
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what you walk on. very thing compared to the rest of earth layers. 3-25 miles thick. broken into pieces called plates or tectonic plates. "plates" float on tectonic plates
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The Lithosphere (cont.)
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2 rock types
continental: granite, less dense oceanic: basalt, more dense |
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The Mantle
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Layer of dense, hot rock
semi-solid, can soften and flow: like plastic 1800 miles thick high pressure softens rock covections currecnts due to great temperature differences from top to bottom. litospheric plates float on mantle |
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The Outer Core
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the only liquid layer
mostly iron and nickel spins as earth rotates and creates magnetic field 2,890-5,150 km thick 4,000-5,000 degrees C |
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The Inner Core
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solid
mostly iron and nickel 5,000-6700 degress C 1,250 km thick (780 miles) heat source-radioactive decay meteroite impacts and weight of overlying material source of iron and nickel is meteroite |
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The theory of plate tectonics
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in 1912, alfred wegner proposed that continents were moving
about 200 million years ago a supercontinent named Pangea began to break apart Formed 2 landmasses, Laurasia and Gondwanaland these landmasses continued to breaked apart into smaller contients that we have today |
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Evidences
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1. continents fit together like a puzzle
2. mountain chain line up 3. rock layers and correlated may be correlated across ocean 4. mineral compostion along south ameria and africa match up 5. rocks of ocean basins are younger than continental rocks |
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Why do the plates move?
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covection cells
due to density differences in mantle warm plastic like rock in mantle rises cooler rock sinks the combination of heat and pressure in the mantle causes the rock to be very mobile plate motion is only a few centimeters per year |
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Divergent Boundary
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plates move apart from each other
new rock is formed where magma exits crust this is called a ridge |
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Divergent Boundaries (cont)
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magma moves up the mid ocean ridge and spills onto the ocean floor creating new rock
this rock is basalt dense and mafic rich in iron and magnesium this is known as seafloor spreading |
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Magnetic Reversals (evidence of seafloor spreading)
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magnetometer: a device for measuring magnetiusm
notice rock on ocean floor magnetized in pattern of symmetrical stripes alternating reverse and normal magnetism |
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Convergent Boundries
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where plates collide or converge
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3 types of convergent boundaries
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1. subduction zone : dense, mafic, basatic ocean crust collides with less dense felsic, granitic continental curst. forms mountains, volcanoes, and ocean trenches.
alaska, washington, oregon alifornia, mt. st. helens, mt. rainer pafic ring of fire |
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Continental collisions
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formation of moutain ranges as one contient collides with another
pushes continents upward and downward extreme heat and pressure high grde metamorphism earhquake activity example: himilayan mountains |
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Ocean to Ocean subduction
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deep sea trenches
volcanic island arcs earthquake activity ex: indonesian islands, mariana islands |
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Transform boundary
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one plates slides past another
marked by linear valleys, stream beds may be cut in half, each half may be moving in opposite direction southern california, san andreas fault |
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San Fransico earthquake
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ruptured the san andreas fult line for 296 miles. most damage from fire
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Hot Spots
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volcanic activity occurs in the center of plates. (away from the boundary)
rising magma melts through the crust examples: hawaii, yellowstone |
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crustal changes
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rock layers can be folded (bent or curved
faulted: displased along a crack due to movement of the lithosphere |
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titled
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slanted
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uplifted
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raised up
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