COMPOSITION Earth consists of distinct layers: the solid inner core, composed mainly of iron and nickel; the liquid outer core, also rich in iron and nickel; the semi-fluid mantle, containing silicate rocks and minerals; and the outermost layer, the crust, made up of lighter rocks like granite (continental crust) and basalt (oceanic crust). Elements like oxygen, silicon, aluminum, iron, calcium, sodium, and potassium constitute the majority, while trace elements contribute to Earth's diverse composition, fostering life and geological processes across its surface.