What is the most common element in the Earth's crust?
Oxygen is the most common element in Earth's crust, making up about 46 percent of its mass. Silicon is second at about 28 percent, followed by aluminum and iron.
In the crust, oxygen is not found mainly as a gas but bonded with other elements in minerals. It combines with silicon to form silicates, the most common group of minerals, which make up most rocks, sand and clay. Quartz, for example, is silicon dioxide.
After oxygen and silicon, the most common elements in the crust are aluminum, about 8 percent, iron, about 5 percent, and calcium, sodium, potassium and magnesium. These eight elements make up more than 98 percent of the crust by mass.
The whole Earth is different
For the planet as a whole, iron is the most common element by mass, because Earth's core is mostly iron. In the atmosphere, nitrogen is the most common gas, at about 78 percent. In the human body, oxygen is the most common element by mass, mainly because we are mostly water.
Did You Know?
Aluminum is the most abundant metal in Earth's crust, but it was once more valuable than gold because it was so hard to extract.