Magma (from the Greek μάγμα, "paste") is the name given to the masses of molten rocks from inside the Earth or other planets. They are generally made up of a mixture of liquids, volatile, and solids.
When a magma cools and its components crystallize, they form igneous rocks, which can be of two types: if the magma crystallizes within the earth, plutonic or intrusive rocks form, but if it rises to the surface, the molten matter is called lava. and when it cools, they form volcanic or effusive rocks (intrusive and effusive are disused terms).
Magmas rise to the surface by flotation (density difference with the environment). The ascent can be rapid and non-stop, producing the superficial exit through a volcanic eruption characterized by its low explosiveness. On other occasions the magma does not reach the surface and stops for a more or less extended period of time, giving rise to the formation of magmatic chambers.
In them, the magma is cooled, generating magmatic differentiation processes through which substantial changes are produced in its chemical composition, as well as in the conditions of the gases dissolved in the magmatic liquid.
There are different types of magma, the most common of which are three main types: basaltic, andesitic and granitic.
Basalt magmas: they can be toleitic, low in silica (-50%) and produced on the ridges, or alkaline, rich in sodium and potassium, produced in areas inside the tectonic plates. They are the most common.
Andesitic magmas: silica content (-60%) and hydrated minerals, such as amphiboles or biotite. They are formed in all subduction zones, whether of continental and oceanic crust.
Granite Magmas - They have the lowest melting point and can form large plutons. They originate in orogenic areas such as the andesitic, but from the basaltic or andesitic magmas that cross and melt metamorphosed igneous or sedimentary rocks of the crust that, incorporated into the magma, alter its composition. On the other hand, according to its mineral composition, magma can be classified into two large groups: mafic and felsic. Basically, mafic magmas contain silicates rich in magnesium and iron, while felsics contain silicates rich in sodium and potassium.
