earth is made mostly of metals and rocks. where did most of the elements that make up these materials (carbon, silicon, iron, etc.) form? earth is made mostly of metals and rocks. where did most of the elements that make up these materials (carbon, silicon, iron, etc.) form? they were produced by stars. they were produced by nuclear fission of uranium and other radioactive materials in space. they were produced by the big bang. they were produced in our sun. they were produced by chemical reactions in interstellar gas clouds.