What process in earths interior causes subduction and sea-floor?

Answer 1

Spreading of seafloor occurs at the mid-ocean rifts, where there is a continuous flow of material rising from the mantle. There is not a unanimously accepted theory as to the cause of the rifting that is taking place. Once the rifting and mantle material inflow has started, however, the conduit is in place. The thinness of the crust at the rift makes it easier for the material to rise, and as it rises it becomes molten and emplaces itself to form new oceanic crust when it solidifies. The rising material is part of a convection current in the Earth's mantle. At the opposite end of the current are subduction zones, where oceanic crust sinks back into the mantle and melts, causing surface features as composite volcanoes. With this cycle of creation and destruction, the total area of seafloor remains relatively stable, but continents change in relative position to each other. These changes do not occur rapidly. The average speed of crustal plate movement is less than the average rate of fingernail growth.

Answer 2

Subduction and sea floor spreading are both a result of the movement of the tectonic plates.
Plate Tectonics

Answer 3

Together, they change the size and shape of the oceans.

Answer 4

The sea floor is being constinty made. As the new sea floor pushes the old sea floor farther away, the old sea floor hits and another plate then the denser plate subducts under into he matle

Answer 5

Plate Tectonics

Answer 6

convection.