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Science 10
Plate Tectonics
| Term | Definition |
|---|---|
| continental drift theory | all continents have not always been in their present day locations and have drifted there over millions of years |
| who proposed the theory of continental drift? | Alfred Wegener |
| what evidence did Wegener use to back up his theory of continental drift? | he said that the coasts of the continents can be aligned and that some continents have similar rocks, mountain ranges, fossils and patterns of paleoglaciation |
| what could Wegener not prove? | he could't give a reason as to how the continents drifted |
| what is a possible mechanism for continental drift? | sea floor spreading |
| what are tectonic plates? | huge slabs of rock that form the earths surface, carry the continents and move over a layer of partly molten rock |
| what was the super continent named? | pangea, meaning all earth |
| paleoglaciation | refers to the extent of ancient glaciers and the rock markings that they left behind |
| volcanoes | are openings in the earths surface, that, when active, releases chunks of rock, gases and melted rock |
| magma | molten rock beneath the earths surface, heated by radioactive material |
| earthquake | a sudden, ground shaking release of built-up energy at or under the earths surface |
| ocean ridges | formed when magma rises to the earths surface, creating new rock while pushing the old rock aside. the farther away from the ridge, the thicker the material |
| mid-atlantic ridge | a mountain range in the atlantic ocean, created by sea floor spreading separates the eurasian plate from the north american plate in the north atlantic and the africa plate from the south american place in the south atlantic |
| sea floor spreading | magma rises to the earths surface because it is less dense, cools and hardens at spreading ridges, forming a new sea floor. convection currents continue to make magma rise, it pushes older rocks aside creates mountain ranges - mid-atlantic ridge |
| paleomagnetism | the study of magnetic properties in ancient rocks |
| earths magnetic field | north and south magnetic field |
| magnetic reversal | when iron and other magnetic material in rocks form they align with the earths magnetic fields and when the direction of the irons motion changes, the earths magnetic poles reverse |
| magnetic stripping | rock on each side of an ocean ridge contains normal magnetic polarity and reverse magnetic polarity |
| magnetometer | detects variations in magnetic fields |
| what did magnetic stripping do? | it provided an explanation for sea floor spreading |
| who proposed the theory of sea floor spreading and when did they propose it? | henry hess, 1960 |
| hot spot | an area where molten rock rises to the earths surface |
| who proposed the theory of plate tectonics and when? | J. Tuzo Wilson |
| how are a chain of volcanic islands formed such as the hawaiian islands? | when a tectonic plate passes over a stationary hot spot |
| layers of the earth from outermost to innermost | crust, upper mantle, lower mantle, outer core, inner core |
| crust | thinnest layer, made up of solid, brittle rock continental crust is granite, oceanic crust is basalt |
| which is denser, oceanic crust or basalt? | basalt |
| mantle | thickest layer, divided into two sections, and upper and a lower. the upper mantle is a liquid but the lower mantle is a solid both layers are made of magnesium and iron |
| the outer core | the second thickest layer, completely liquid, full of iron and nickle |
| the inner core | the third thickest layer lying at the earths center, made of iron and nickle solid due to the immense pressure the inner core and outer core rotate at different speeds and may be responsible for earths magnetic field |
| lithosphere | makes up the earths crust and the upper upper mantle |
| asthenosphere | makes up the lower upper mantle |
| mantle convection | a recurring current in the mantle that occurs when hotter, less dense material rises, cools and then sinks again (like a candle) one of the driving forces behind plate movement |
| spreading ridge/ocean ridge | if a spreading center occurs in the ocean |
| rift valley | if a spreading center occurs on land |
| ridge push | when new material pushes old material aside, forcing the tectonic plates away from the ridge |
| subduction | the action of one plate pushing under another plate |
| subduction zone | where the subduction occurs, usually creating earthquakes and volcanoes |
| slab pull | when the tectonic plate gets subducted deep into the mantle it pulls the rest of the plate with it |
| plate boundary | the region where two tectonic plates are in contact |
| divergent plate boundaries | mark the areas where plates are spreading apart |
| convergent plate boundaries | occurs when plates collide |
| oceanic-oceanic convergence | when oceanic plates collide also creating subduction zones which result in a volcanic island arc |
| continental-continental convergence | when continental plates collide, the plates hit each other, folding and crumbling, resulting in mountain ranges |
| oceanic-continental convergence | when a dense oceanic plate collides with a light continental plate the oceanic plate gets subducted, creating mountain ranges, volcanoes/volcanic belts and trenches |
| transform plate boundaries | when tectonic plates slide past each other, creating transform faults |
| focus | the location inside the earth where and earthquake starts and where the energy is first released |
| epicentre | the point directly above the focus where the earthquake first reaches the earths surface |
| P-waves (primary waves) | the fastest traveling waves, they stretch like a spring and can travel through liquids, solids and gases |
| S-wave (secondary waves) | slower than p-waves, ground compresses and stretches at right angles to the direction of the waves motion, can travel through solids |
| L-wave (surface waves) | slowest waves, but the most damaging these waves roll along the earths surface |
| seismometer/seismograph | measures the amount of ground motion cause by an earthquake |
| seismogram | the record of ground motion |
| composite volcanoes | conical shaped volcanoes that occur over plate boundaries, letting out very thick lava due to high pressure build up |
| shield volcanoes | the largest volcanoes on earth that occur over hot spots, producing thinner magma that flows easily |
| rift eruptions | occur when magma erupts through long cracks in the lithosphere, producing immense amounts of lava |
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Mid-Term
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