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Wednesday, October 13, 2004 thy of plate tects- oceanic floors are spreading aprt, away from ridges, propelled by thermal convection currents - spreading occurs > fractures in rift valley > magma swells up> new crust is formed - ( process repeats) - convection currents in mantle than carries crust away from ridges into deep sea trenches . - there, oceanic crust decends with decending convectional current, is melted and reaborbed. - oceanic crust regenerates in 200 -300m yrs. the sec part of the thy.. the mantle convection thy part mantle convection current essentially: the movement of continental plates on convectional currents which occur within teh earths mantle due to heat transfer from the core - rigid lith carries the continental plates and move in constant motion relative to one another. they slide over the mobile asthenosphere. - the energy source for movement - earth's internal heat. transferedby convection currents. - hot material rises to the base of the lith, moves lat, cools, decends.
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