how does the mantle convection hypothesis explain plate movements at divergent boundaries and subduction bound

Answer 1

I'm not an expert, but just rationally thinking about this would be similar to a pot of boiling water. If something is on top of the convection wave, it is moved away from the centre of the convection current (the hottest part).

Likewise, as the the convection wave moves up and outward and back down to the point of origin, the earth's plates "float" with this motion and because the plates are solid, they have to go someplace when and where they impact. The plate that contains the heavier, or more mass, subducts under the "lighter" plate.

Occasionally, the thin part of a plate will slide over a "hot spot" where the magma "boils" through the plate and forms a volcano - and the rest - - -

Answer 2

The mantle is a material that is a very viscous fluid. Its not a solid, but at the same time it is not a liquid. When a fluid is heated, heat energy makes molecules move faster and increase the volume of the fluid. With the same amount of molecules present, this has the effect of reducing the density so the heated fluid becomes less dense and rises above the denser cooler fluid.

Deep within the earth there is a large amount of heat coming from two sources: the magma remnants of the Great Bombardment, and radiation from radioactive elements. This heat, in accordance with the 2nd law of thermodynamics, must flow to a cooler place, and subsequently rises to the surface of the Earth.

If the Earth were smaller, this heat would flow by conduction, but because of the relatively large size of the Earth, convection also takes place. What this means is that convection currents are established within the earth, which bring warm material to the surface and send cooler material to the interior.

In one section of the mantle convection currents are moving in a clockise direction going around and around, while nearby there is another convection current which is moving in an anticlockwise direction. What this means is that there is one plate, for example the american plate floating on one current with the european plate floating on the other. Because the currents are moving in opposite directions means that the plates will move in the same manner. The mid atlantic ridge is the result of these diversgent boundaries and it is exactly the same process that effects subduction zones.

Answer 3

It really doesn't. That's where they're kind of iffy about their science.