Inside the Earth - Get a Move On!
What forces can be large enough to move these tectonic plates, enormous chunks of crust and rock, around Earth? What is strong enough to cause earthquakes, volcanic eruptions, mountain building, plateau formation, and all of the other continuously occurring geological processes?
Scientists are still not exactly sure, since the forces are unseen and can't be viewed, but we have a good guess. Our best idea is that the core of Earth is radioactive and continuously emitting heat, along with residual heat caused by gravitational energy left over from the formation of Earth.
This heat is causing convection currents which act much like a conveyor belt, causing the plates to move around on the semi-liquid material of the asthenosphere. Convection currents or convection cells are caused when heated material becomes less dense and rises up through the mantle. This material then cools, condenses, and sinks back towards the core, where it is reheated and the process cycles. You have probably observed this action if you have watched water boil or a pot of thick soup simmer on the stove. This process within Earth is MUCH slower, but it operates in a similar way.
How many convection cells are there within Earth? Where and how do they originate? What is their structure? How the plates move is still a mystery. Scientists think convection cells have something to do with plate movement. Recently scientists have added density and gravity to their list of explanations of how plates move. They believe that gravity pulls the denser edges of some plates down toward the center of the Earth. When the edge is pulled down toward the Earth’s center, the rest of the plate must follow which causes the plate to move. Because these forces are buried so deeply, we cannot test and prove any idea beyond a reasonable doubt. How and why this energy coming from the core to the surface concentrates into these cells remains a mystery. Because these forces are buried so deeply, we cannot test and prove any idea beyond a reasonable doubt. It is a good thing that we do not have to understand the motion for the motion of the plates to occur!