1. Oxygen (O): It makes up about 46.6% of the Earth's crust by weight. It is found in many common minerals like quartz (SiO2), feldspar, and mica.

2. Silicon (Si): It makes up about 27.7% of the Earth's crust by weight. It combines with oxygen to form silica (SiO2), which is a fundamental component of many rocks and minerals.

Together, oxygen and silicon make up over 74% of the Earth's crust.