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7th gr Earth
Term | Definition |
---|---|
fossil | remains or impression of a prehistoric organism preserved in petrified form or as a mold or cast in rock |
superposition | layers of rock are dated by oldest on bottom and youngest on top |
plate tectonics | theory that explains how the surface of the Earth changes |
seafloor spreading | formation of new areas of oceanic crust |
density | mass/volume |
lithosphere | solid outer crust |
asthenosphere | molten upper portion of the mantle |
convection currents | circulating currents in the mantle move the plates above |
slab pull | subducting slabs are pulled by gravity to the center of the Earth |
divergent boundaries | plates separate |
rift valleys | large elongated depression with steep walls; Continental - Continental divergent |
mid ocean ridges | ridge system situated in the middle of an ocean basin; Oceanic - Oceanic divergent causing ocean basin to widen |
convergent boundaries | plates collide; Continental - Continental convergent causes mountains to form |
subduction zones | occur when a more dense oceanic plate is forced down into the mantle; Continental - Oceanic convergent; in the ocean they form deep ocean trenches and volcanoes |
volcanic island arcs | a belt of volcanoes formed above a subducting oceanic tectonic plate |
ocean trenches | long, narrow depressions on the seafloor; deep chasms |
transform boundaries | plates pass by each other; area where faults and earthquakes form |