What are geological materials

The structure of the earth

In the early stages of its history 4,567 million years ago, the earth was a homogeneous planet with roughly the same material composition everywhere inside.

After only a relatively short time - within the first hundred million years - there was a profound restructuring of the earth due to increasing warming (through accretion of falling matter, compression of the earth's core, radioactive decay). After it had warmed up to around 2000 ° C (melting point of iron), the liquid metal collected in drops. Since iron is heavier than the other common constituents of the earth, about a third of the earth's matter sank to the center and formed the iron core there, while at the same time lighter material was displaced from the core area.

During this huge, high-temperature displacement process, other parts of the earth were also partially melted. In contrast to iron, however, these melts were lighter than the starting material from which they were separated, and they therefore rose to the surface, where they cooled and formed a crust.

A dense earth core made of iron developed in the center, on the outside an earth crust made of light material (oxygen, silicon, aluminum, calcium, sodium, etc.) Iron silicates). Eventually, large continents of lighter material formed, floating like clods on this crust.

Today all of this seems quite obvious and familiar to us, but what evidence do we have, since we can only drill a maximum of 12 km into the earth's interior. On the one hand there are seismological data that confirm this model, and on the other hand we can compare the development of the earth with the other celestial body and partly correlate it.
Now the other celestial bodies are even further away than the earth's core, so what helps us there? Well there is one exception. The asteroids. In the asteroid belt there are bodies that have undergone a similar differentiation process in the core-mantle-crust as the earth. How do we know? Fortunately, some of these bodies leave their place in the solar system and come to earth as meteorites.

The Babylonians knew meteorites as rare structures; We know from ancient inscriptions that they were referred to as that which fell from heaven (ancient Egyptian iron: metal from heaven; Greek sideros = iron corresponds to the Latin sidera for stars, orbits). This prehistoric knowledge and the knowledge about the origin of iron from space were lost or rejected in the Middle Ages, and it was not until 1794 that Chladni "rediscovered" its extraterrestrial origin on an iron meteorite that fell in Siberia.
On the basis of the different types of meteorites that are found, it can now be proven that many meteorite parent bodies (planets, asteroids) must have undergone a differentiation corresponding to that of the earth (roughly simplified: iron meteorite ~ core, stone-iron meteorite ~ mantle, stone meteorite (Achondrite) ~ crust).

Through this long-term differentiation, the lighter elements continuously entered the outer layers of the earth, and it initiated the escape of even lighter gases, which eventually led to the creation of an atmosphere and the oceans. Even today, huge amounts of gases escape from the interior of the earth when volcanic eruptions occur.