Earth Layers

There are three main zones to the Earth’s interior. The crust is the outer layer of rock which forms a thin skin over the Earth. Below this lies the mantle, a thick shell of rock that separates the crust above from the core bellow. The core is the Earths central zone. It is probably composed of metal and is the source of the Earth’s magnetic field.

The earths inner core is a solid ball of what is believed to be composed of an iron-nickel alloy with some other elements. It has a radius of about 1,220 km. There are no samples of the earths core and information comes mostly from analysis of seismic waves and Earth’s magnetic field. The temperature of the inner core’s surface is estimated to be around 5,430 Celsius which is about the temperature at the surface of the Sun.

The earths outer core is a fluid layer and is similar in composition to the inner core although it is not under enough pressure to be a solid. It is about 2,400 km thick. The temperature of the outer core is estimated to be about 2,730 – 4,230 Celsius in its outer region 3,730 – 7,730 near the inner core.

The Earths magnetic field is believed to be generated by electric currents in the cores conductive iron alloys and created by convection currents due to heat escaping from the core.

The Earths mantle has a depth of 2,890 km which makes it the planets thickest layer. The mantle is composed of silicate rocks which are richer in iron and magnesium than the overlying crust. Convection of the mantle drives the motion of the tectonic plates in the crust.

The Earths lithosphere includes the crust and upper mantle which forms the hard and rigid outer layer of the Earth. The lithosphere subdivided into tectonic plates and is underlain by the semi-fluid asthenosphere.

The earth crust is made up of oceanic crust and continental crust. The oceanic crust is much thinner and is denser than the continental crust. The average thickness of the oceanic crust is 7 km and the average thickness of the continental crust is 30 to 50 km which is thickest under mountains.