Final answer:
Oxygen is the most abundant element in the Earth's crust, followed by silicon. Aluminum and iron are also present but in lesser amounts.
Step-by-step explanation:
Oxygen is the most abundant element in the Earth's crust. It accounts for 94% of the crust by volume and 47% by weight. Silicon is the second most abundant element, making up 1% of the crust by volume and 28% by weight. Aluminum and iron are also present but in lesser amounts compared to oxygen and silicon.