The Structure

The Earth's structure is composed of multiple layers. The outermost crust is around 19 miles (30 km) thick from land (continental crust) and only 6 miles (10 km) thick beneath the oceans (oceanic crust). Below the outer crust is the lithosphere which consist of several crustal-plates that slide over the less rigid and thick asthenosphere level below. Collisions between the plates produce folded mountains, and zones of seismic activity are concentrated along the plate boundaries. The lithosphere and asthenosphere layers are 75-125 km and 100-700 km thick, respectively. At the centre of the Earth lies the core, comsisting of an outer molten metallic core of iron and nickel, surrounding a potentially solid inner core with a temperature of around 4000°C (7200°F). A silicate mantle overlies the core.