The most abundant element in the Earth's crust is oxygen (O).Top Elements in Earth's Crust (by weight percentageOxygen (O) - 46.6%Silicon (Si) - 27.7% Aluminum (Al) - 8.1%Iron (Fe) - 5.0% Calcium (Ca) - 3.6%Sodium (Na) - 2.8% Potassium (K) - 2.6%Magnesium (Mg) - 2.1%But Why oxygen is so abundant?Oxygen mostly exists in the crust as part of compounds, especially silicate minerals (like quartz, feldspar, mica).For example, SiO₂ (silicon dioxide) is a common compound in rocks.