The Earth's crust is composed of several minerals and elements, including iron, oxygen, silicon, magnesium, sulfur and nickel. Present in smaller amounts are calcium, aluminum and several other elements. The crust is the outermost portion of the Earth, which is comprised of three layers.
Directly beneath the Earth's crust is the mantle. It is several hundred miles in depth and, like the Earth's crust, contains various types of minerals. Magnesium and iron are found in silicate rocks in the mantle. Volcanoes can originate from the mantle as heat causes the silicate rocks to rise up. Upon cooling, they sink back into the core. This action causes tectonic plates to move, pushing the mantle through the crust and causing a volcano.
The innermost layer of the Earth is termed the core. The core has two layers, a solid inner core and a more liquid outer core. Both parts of the inner core are several hundred miles thick. The inner core spins at a speed that is different from the rest of the Earth, generating the magnetic field of the Earth. Northern and southern lights, known as auroras, are the result of charged particles colliding with molecules above the Earth's magnetic poles.