The correct answer is the "crust." The Earth's crust is the outermost layer of the planet, consisting of solid rock that forms the Earth's surface. It is composed of a variety of elements, including silicon, oxygen, aluminum, magnesium, iron, calcium, sodium, and potassium. The crust is relatively thin compared to the other layers of the Earth, with an average thickness of about 25 miles (40 kilometers). There are two types of crust: the continental crust, which makes up the land areas, and the oceanic crust, which is found beneath the ocean basins.
