What causes convection currents inside earth

Differential heating and pressure.

Convection currents occur when lighter (or not as dense) warm materials rise over cooler, more dense, and heavier material sinks below it. These movements occur inside the mantle, or the third from inner-most layer of the Earth, and are often the cause of tectonic plate moment.

the wires in the toaster turning red and the toast crisping and turning brown

i think it is dna, i'm not totally sure but i think it might be.