structure of the Earth
The rocks, soil and water on the surface of the Earth make up only a tiny fraction of the total mass and volume of the Earth. Centuries ago, people used to think that the Earth was flat, or even a hollow sphere. Today, by monitoring vibrations in the Earth caused by earthquakes, and examining the rock erupted out by volcanoes, we know that the Earth has a complex layered structure. This topic investigates the internal structure of the Earth.
The layered Earth
The outermost physical layer is the lithosphere (LITH uhs feer). Thin, cool and solid, the lithosphere contains the crust and some of the mantle. Composed mainly of silicates, it "floats" on the underlying asthenosphere.
The asthenosphere (as THEHN uhs feer) is hotter and in a semi-liquid state. Starting at around 80 to 100 km deep, the rock in the asthenosphere slowly flows in a plastic state moving in a circular motion creating convection currents of hot rock. This moves heat from deep within the mantle towards the surface. It is this movement which helps move the continents and creates volcanoes and lava flows.
Next is the mesosphere. Comprising the inner part of the mantle, the mesosphere is a region of very hot solid rock. Here, although hotter than the asthenosphere, the pressure is too high for liquid rock to form.
The core is divided into two parts, the liquid outer core, where temperature wins over pressure and the solid inner core where again the pressure is too high for a liquid to form.
Moving in from the surface to the centre of the Earth you could expect to getter hotter and be subjected to ever increasing pressure, but you would go from solid, through flowing semi-liquid plastic rock to solid, liquid and finally solid again at the centre.
A quite different journey to Jules Vernes' "Journey to the centre
of the Earth".