What is Earth made of? The Earth is made out of many things. Deep inside Earth, near its center, lies Earth's core which is mostly made up of nickel and iron. Above the core is Earth's mantle, which is made up of rock containing silicon, iron, magnesium, aluminum, oxygen and other minerals. The rocky surface layer of Earth, called the crust, is made up of mostly oxygen, silicon, aluminum, iron, calcium, sodium, potassium and magnesium. Earth's surface is mainly covered with liquid water and its atmosphere is is mainly nitrogen and oxygen, with smaller amounts of carbon dioxide, water vapor and other gases.