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Science plates
Science tectonic plates, earthquakes, volcanoes grade 8
| Question | Answer |
|---|---|
| continental drift | Wegner's hypothesis that all continents were once connected in a single, large lanmass that broke apat about 200 million years ago and drifted slowly to their current positions |
| pangea | large, ancient landmass that was composed of all the continents joined together |
| sea floor spreading | Hess's theory that bew sea floor is formed when magme is forced upward toward the surface at a mid-ocean ridge |
| plate tectonics | theory that earth's crust and upper mantle are broken into plates that float and move around on a plasticlike layer of the mantle |
| plate | a large section of the earth's oceanic or continental crust and rigid upper mantle that moves around on the athenosphere |
| lithosphere | rigid layer of Earth about 100 km thick, made of the crust and a part of the upper mantle |
| asthenosphere | plasticlike layer of Earth on which the lithosphere plates float an move around |
| divergent boundaries | the boundary between two plates that are moving apart |
| convergent boundaries | when 2 plates move together |
| subduction zone | the area where an oceanic plate subducts, or goes down into the mantle |
| transform boundaries | when two plates slide past one another |
| earthquake | movement f the ground that occurs when rocks inside Earth pass their elastic limit, break suddenly, and experience elastic rebound |
| faut | fracture that occurs when rocks change their shape by breaking; can from as a result of compression(reverse fault), or shear(strik-ship fault) |
| focus | point deep inside Earth where energy is released, causing an earthquake |
| epicenter | point on earth's surfance directly above an earthquake's focus |
| seismograph | instrument used to recored seismic waves |
| magnitude | a measure of the energy released by an earthquake |
| tsunami | powerful seismic sea wave that begins over an ocean-floor-earthquake; can reach 30 minutes height when approaching land, and can cause destruction in coastal areas |
| seismic safe | describes the ability of structures to stand up against the vibrations caused by an earthquake |
| volcano | cne-shaped hill or mountain fromed when hot magma, solids, and gas errupt onto Earth's surface through a vent |
| shield volcano | large, broad volcano with gently slping sides that is formed by the buildup of basaltic layers |
| cindercone volcano | relativly small volcano formed from alternating layers of violent erruptions of tephra and quieter erruptions of lava |
| rift | long crack that forms between tectonic plates moving apart at plate boundaries |
| hot spot | large, rising body of magma that can force its way through Earth's mantle and crust and can form volcanoes |
Created by:
polarbears1
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