The formation of magma within the mantle and crust requires a great amount of heat. Much of this heat comes from the radioactive decay of elements such as uranium, thorium, and potassium. Due to the process of radioactive decay, the heat produced early in the Earth’s history was greater than that currently produced. The heat produced today is greater than will be produced in the future. How might the chemistry and distribution of igneous rocks change in the future? Would you expect more or fewer volcanoes?