Though you may guess that the majority of the Earth is made up of something metallic like aluminum or something rocky like calcium, the element that makes up nearly half of the Earth is oxygen. Here is the list of elements by weight proportion in the Earth’s makeup:

  1. Oxygen= 46.6%
  2. Silicon= 27.7%
  3. Aluminum= 8.1%
  4. Iron= 5.0%
  5. Calcium= 3.6%
  6. Etc.

As oxygen is one of the most highly reactive elements in the universe, most of this oxygen that makes up the Earth is bound up with other elements in the form of oxides.