The layers of the Earth rest upon each other because in each layer, the density or the state of matter are different. For example, the crust lays on the mantle, but the mantle is solid. This is because the mantle is made of magnesium and iron, and that is denser than basalt and granite, so the crust does not sink below the mantle.
Crust
The crust is the outermost layer of the Earth. It is the solid ground we stand on, the part that consists of basalt and granite. The crust's thickness can vary depending on whether it is oceanic or continental. The oceanic crust is thin and very dense, whereas the continental crust is very thick and not at all dense.
Mantle
The mantle is liquid-like layer that consists mostly of magnesium and iron. The mantle has three parts, the upper mantle, middle mantle, and lower mantle. In the middle mantle convection currents occur. Convection currents help move tectonic plates. The convection currents work because cool fluid sinks, and warm fluid rises.
Outer Core
The outer core is composed of liquid iron nickel, and is about 2,000 kilometers thick. *
Inner Core
The inner core is a solid ball of nickel and iron at the center of the earth and is about 1,250 km thick.*
*No one has gone down to the center of the Earth, so scientists have created their own seismic waves to detect the difference between materials. This method is not something everyone agrees on, but the majority of people believe this is method is legitimate and correct.
Seismic waves- A seismic wave is like a shock wave earthquakes put off that as they travel through matter get slower and weaker, like the waves of a pebble thrown in a pond.
Seismic waves- A seismic wave is like a shock wave earthquakes put off that as they travel through matter get slower and weaker, like the waves of a pebble thrown in a pond.