Science: C3+4-1

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Pangaea

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The name of the single landmass that began to break apart 200 million years ago

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Fossil

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The preserved remains or traces of an organism that lived in the past

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Mid-ocean ridges

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An undersea mountain chain where new ocean floor is produced; a divergent plate boundary

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Sea-floor spreading

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The process by which molten material adds new oceanic crust to the ocean floor

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Deep-ocean trenches

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A deep valley along the ocean floor beneath which oceanic crust slowly sinks towards the mantle

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Subduction

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The process by which oceanic crust sinks beneath a deep-ocean trench and back into the mantle at a convergent plate boundary

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Plates

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A section of the lithosphere that slowly moves over the asthenosphere, carrying pieces of continental and oceanic crust

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Divergent boundary

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A plate boundary where 2 plates move away from each other

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Convergent boundary

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A plate boundary where 2 plates move toward each other

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Transform boundary

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A plate boundary where 2 plates move past each other in opposite directions

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Faults

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A break in Earth's crust along which rocks move

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Rift valley

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A deep valley that forms where 2 plates move apart

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Stress

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A force that acts on rock to change its shape or volume

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Normal fault

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A type of fault where the hanging wall slides downward; caused by tension in the crust

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Tension

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Stress that stretches rock so that it becomes thinner in the middle

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Reverse fault

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A type of fault where the hanging wall slides upward; caused by compression in the crust

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Compression

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Stress that squeezes rock until it folds or breaks.

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Strike-slip fault

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A type of fault in which rocks on either side move past each other sideways with little up or down motion

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Shearing

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Stress that pushes masses of rock in opposite directions, in a sideways movement

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Plateau

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A large landform that has high elevation and a more or less level surface

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What was Wegener's hypothesis about the continents?

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Wegener's hypothesis was that all the were once joined in a single landmass and have since drifted apart.

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Evidence from land features

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Mt. ranges on South America line up, and coal fields in Europe and North America match up

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Evidence from fossils

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Some of the same Fossils became separated once Pangaea split apart

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Evidence from climate

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Tropical fossils have been found near the poles; this means that this place was near the equator, but drifted toward the poles

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Why was Wegener's hypothesis rejected?

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He couldn't identify the cause of continental drift, but we have found that it's from convection currents.

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What did scientists use to map mid o. r.?

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Sonar- uses sound waves to measure the distance to an object

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What is sea f. S.?

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S.f.s. adds more crust to the ocean floor. At the same time, older strips of rock move outward from either side of the ridge.

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Evidence from ocean material

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Pillow lava- when molten material hardens quickly after erupting underwater

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Evidence from magnetic stripes

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Rock lines up in the direction of Earth's magnetic poles, poles occasionally reverse themselves

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Evidence from drilling samples

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Rock farther from a ridge: older, vice versa

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The process of subduction

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As oceanic cools, it gets more dense; when it collides with continental crust, it sinks into the mantle, because it is more dense; sinks into a deep ocean trench

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Subduction and Earth's Oceans

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Subduction and sea floor spreading can change the size and shape of the oceans; ocean renewed about every 200 mil. yrs. Oceans get bigger when crust forms faster than it can sink into the mantle, vice versa

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Plate motions over time

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Scientists use satellites to measure plate movement, move 1-12 cm. per year

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How does stress change Earth's crust?

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Tension, compression, and shearing

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How do faults form?

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When enough stress builds up in rock, the rock breaks, creating a fault

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Folding Earth's crust

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Rocks stressed by compression can bend without breaking and can form anticlines and synclines

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Stretching Earth's crust

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Fault block mts.- when hanging walls slip down, the footwall stays up and forms into a mt.