Science of structure, composition and structure of the Earth's crust (Earth = Ge), its physical properties and its history of development as well as the forming processes. The term was first used in 1778 by the Swiss meteorologist Jean-André Deluc (1727-1817); before, geognosy was in use. The earth's crust consists of three different rock formations. These are crystalline or solidified rocks, sedimentary or stratified rocks and metamorphic or deformed rocks.
Crystalline or solidification rocks: These are caused by cooling and solidification. The plutonic rocks (plutonites) are formed when ascending magma slowly cools down long before it reaches the surface of the earth and is then mineralized in large crystals. The most common crystalline plutonic rocks are granite, mica schist and gneiss. As molten magma fades closer to the surface of the earth or into the vent of an extinct volcano, it increasingly crystallizes into fine and fine crystals due to the faster cooling processes, forming hard, dense solidification rocks such as basalt or obsidian. In the eruptive rocks (volcanic rocks), liquid magma ignites eruptively as lava to the earth's surface to cool in the water or in the air. From the eruption ash precipitate arise gas-filled tuff rocks, while the porous solidified lava flows to fertile lava soils weather.