The Comparative Abundance of The Elements - There are 92 naturally occurring elements, only 17 of them make up 99.5% of the earth's crust (including oceans and atmosphere). - In living things (plants, animals, people) the six most abundant elements are carbon, hydrogen, oxygen, nitrogen, phosphorus and sulfur. - The universe is dominated by the elements hydrogen (83%) and helium (16%) 1. The Crust The outside of the earth is a thin crust which is approximately 20 to 40km thick. The crust is a formation of dips and hollows which are filled with water to form the oceans and seas. On top of the earth's crust is an atmosphere, this is a thin layer of gases