What drives the motion of the plates on the earth?,geophysical and geochemical evidence for mantle convection?

Question

What drives the motion of the plates on the earth?,geophysical and geochemical evidence exists for mantle convection? Is the whole mantle convecting or just part of it?

Answer 1

Plate motion is mainly driven by density, which causes subduction and mid-ocean ridges (sea floor speading).

A mid ocean ridge is an area where new sea floor is created throught the divergent (speading) motion of the tectonmic plates in that area. It comes down to density. The center of the ridge is high, because it it new (just formed) and hot. The edges are low because it is old and cold. There are two main theories on the cause: slab pull and ridge push.

Ridge push is the classic idea that the ridge is a high point of a convection current, pushing the plates aside and allowing new mantle material to rise up and fill the hole.

Slab pull is the new idea that the subducting end of the plate, that is really old and dense, pulls on the entire plate as it subducts, and thus pulls apart itself in places, causing a hole which is then filled by rising material, forming the ridge.

It's kinda a chicken/egg thing, so we may never be able to rule one or the other out.

Geochemical evidence (isotopes showing mantle source in MORBs) and geophysical evidence (deepest earthquakes at subduction zones) supports the fact that this occurs, but does not specifically address the cause.

Answer 2

The mantle is a chemically distinguished layer and consists mainly of the rock peridotite. Mechanical layers divide the mantle into 3 parts: the Lithosphere, the Aesthenosphere, and the Mesosphere. The lithosphere (10 to 200 kilometers thick) is rocky and fairly well attached to the crust of the Earth, though it has a different chemical composition than the crust. It is the presence of the lithosphere that gives the tectonic plates strength enough to not break up.

Immediately below the lithosphere is the aesthenosphere. This layer is what scientists term "plastic." Basically it is hot enough that it is not rocky, but it is not a fluid either. The best comparison for it is Silly Putty. This is the layer that convects heat.

Below the aesthenosphere, at a depth of 660 kilometers, the mesosphere is a part of the mantle that is hot, but is under so much pressure that it is solid and rocky.

It is important to note that scientists are still not sure what drives continental drift and convection is only one theory and likely only one of many components that cause drift.

Answer 3

the main effectual utilising tension for mantle convection is known to be the warmth released from thermonuclear decay of radioactive aspects. the main effectual aspects accountable are concept to being uranium, thorium and potassium. even nonetheless potassium releases little power whilst compaired to uranium and thorium, the huge volume of potasium compaired to the hint quantities of uranium and thorium skill the little atom can compete with its larger brothers in springing up convection. at contemporary there are 2 theories of mantle convection: finished mantle convection and a couple of 0.5 mantle convection. because no-one has been to the mantle, geochemical evidence isn't uncomplicated again via. additionally, because of the fact the mantle convects slowly, geophysical evidence isn't uncomplicated again via. some xenoliths and a few stony meteorites supply somewhat geochemical evidence, yet it incredibly is all.