The elements that comprise most of the Earth's crust are oxygen and silicon.

Here's why:

* Oxygen (O): Makes up about 46.6% of the Earth's crust by weight. It's found in many common minerals like quartz, feldspar, and mica.

* Silicon (Si): Makes up about 27.7% of the Earth's crust by weight. It combines with oxygen to form silicates, which are the most common mineral group in the crust.

Together, oxygen and silicon account for over 74% of the Earth's crust by weight.