How do differences in density and temperature cause sea-floor spreading and subduction?
1 Answer
The cooler denser mantle sinks causing subduction and the hotter mantle rises to the surface causing sea floor spreading.
Explanation:
In a convection current the hot material rises to the surface, When the material reaches the surface it starts to cool off and spread out. This causes the sea floor spreading observed at the mid ocean ridges.
In a convection current the cooler material sinks back down completing the cycle of the convection current. At a subduction zone the cooler material of the mantle sinks back down into the hotter mantle carrying the crust with the segment of cooler mantle.
Also the Ocean plates are made of basalt which is much more dense than the granite base of the continental plates. This causes the ocean plate to be the plate than sinks down into the mantle.
How thick layers of ocean sediments have ended up on the Continents is not explained by the cycle of sea floor spreading and subduction zones.
