Final answer:
Oxygen is the most abundant element in Earth's crust, making up about 46.1% by mass, which is substantially more than any other element there.
Step-by-step explanation:
The most abundant element in Earth's crust is Oxygen. While hydrogen is the most abundant element in the universe, primarily composing stars like our Sun, it is not as abundant in Earth's crust. Oxygen makes up approximately 46.1% of the Earth's crust by mass and often exists in combination with other elements like silicon, which itself accounts for 28.2%. This makes oxygen tremendously more abundant than hydrogen, nitrogen, and silicon in the Earth's crust. Notably, silicon is the second most abundant element in the crust, so in a list of abundant elements, oxygen would be first followed by silicon.