Inside the earth, near its core, there is a flowing mass of molten iron. the movement of this liquid metal, in convection cells, causes the earth's crust to shift, as part of the plate tectonics process. to transform iron into its liquid state requires an incredible amount of energy. at least 50% of this energy comes from the
a) sun's radiation.
b) volcano eruptions.
c) earth's magnetic energy.
d) decay of radioactive isotopes.