The most abundant element in the Earth's crust is oxygen. Accounting for about 46% of the Earth's crust by weight, oxygen is primarily found in the form of compounds, such as silicates and oxides. It combines readily with other elements, such as silicon, aluminum, iron, and calcium, forming various minerals. The abundance of oxygen is critical for numerous geological, biological, and chemical processes. It plays a vital role in supporting life, as it is essential for respiration in animals and photosynthesis in plants, making it a fundamental element in understanding Earth's systems.