Final answer:
Oxygen is the most abundant element in the Earth's crust, making up about 46.6% by weight and approximately 50% of the crust's mass.
Step-by-step explanation:
The most abundant element in the Earth's crust is oxygen, which accounts for about 46.6% by weight. Oxygen is principally combined with silicon to form silicates, which are the dominant minerals in the Earth's crust. Notably, oxygen makes up approximately 50% of the crust's mass and it is involved in various forms, including as O₂ in the atmosphere and as part of silicate minerals.