LAYERS OF THE EARTH

There are multiple layers of the Earth. The crust, the mantle, the outer core, and the inner core. There are also the layers that are considered to part of the lithosphere and asthenosphere. Each layer has its own properties, make-up, and characteristics. 

Billions of years ago, the Earth started out as a hot, gooey ball of rock. The heaviest material sank to the center of the Earth, while the lighter material floated to the top to form the crust. If the earth were an hard-boiled egg, the crust would be around the thickness of the egg shell, the mantle would be the egg white, and the core would be the yolk.

CRUST

This is the layer we live on. It's solid but brittle, and is the thinnest layer on earth; around 5-70 km thick. The thickness varies in different parts of the crust. Continental crust is approximately 70 km, and is made from granite. While, Oceanic crust can be as thick as 10 km and is made from the dense rock basalt. As the crust is on the surface, most of the lighter materials (like silicon and oxygen) exist here because it is less dense. In fact, 3/4 of the earth's crust is silicon and oxygen, which combine to form silicate rocks.

LITHOSPHERE 

 The lithosphere consists of the crust and the uppermost layer of the upper mantle. Together, these make up the tectonic plates. The thickness is around 65 km - 100 km and can be broken down into 15 main plates.

ASTHENOSPHERE

This layer is part of the upper mantle where it's partly molten (or semiplastic). The asthenosphere is believed to be one of the causes of plate movement, because this is the layer where mantle convection takes place. Convection happens when particles get heated, which equals more kinetic energy. That means that particles with more heat and energy will spread apart, making the magma less dense, therefore causing it to rise. The magma cools, sinks back down, and the cycle repeats. It is also thought that the temperature here varies, because of the different amounts of radioactive elements that are present. 

MANTLE

The upper and lower mantle combined, make up the thickest layer. It is 2900 km thick and 70% of earths volume. The upper mantle is partly molten rock and has the consistency of toothpaste. The lower mantle however is dense and solid. Both are mostly iron and magnesium. 

OUTER CORE

The outer core is believed to be comprised of mostly an iron and nickel alloy because calculations of it's density and the fact the iron and nickel also make up many meteorites. Because of the high temperature,  the outer core is 2300 km of liquid.

INNER CORE

The inner core, like the outer core, is for the most part, made from iron and nickel. But unlike the outer core, this layer is solid. Although the temperature here is around 5000°C - 6000°C (which is four times the melting point of iron), due the the extreme pressure of all the other layers, atoms crowd too close together, preventing the liquid state.