Igneous is a term that derives from the Latin word igneus . The concept is used to name that which is linked to fire .
For example: “The firefighters were alerted at dawn of the existence of a fire source in the middle of the forest,” “The fire destroyed several homes and left three people injured,” “The explosion generated a fire process that could only be suffocated several hours later.”
In the field of geology , the rock that arises from the solidification of magma found inside the planet Earth is classified as igneous . Igneous rocks are produced when molten matter cools and thus solidifies.
Depending on the way in which cooling occurs, it is possible to differentiate between different types of igneous rocks. When this cooling is generated on the surface and quickly, we speak of volcanic rocks , also called extrusive or effusive rocks. In this case, which occurs when a volcano erupts, the rock crystals cannot be distinguished with the naked eye.
If, on the other hand, the cooling process is underground and develops slowly, igneous rocks are called intrusive or plutonic rocks and have large crystals .
Most igneous rocks are plutonic, such as granite , diorite , and tonalite . Among the volcanic igneous rocks, basalt , obsidian and rhyolite appear.
It is estimated that about 95% of the upper sector of the Earth's crust corresponds to igneous rocks. An extensive layer of metamorphic rocks and sedimentary rocks is distributed over them.
The importance of igneous rocks for geology is considerable, and this is due to the following characteristics:
* between its minerals and its global chemistry, they provide a series of data about the composition of the Earth's mantle (an internal layer from which the magma that gives rise to igneous rocks comes) and the pressure and temperature conditions that They reign at the moment in which the rock is formed or from the previous one, the one that must have been melted;
* The absolute age of igneous rocks can be determined through various radiometric dating systems, a procedure that can also be applied to organic and mineral remains. In this way it is possible to compare them with adjacent geological strata and establish a temporal sequence of the different events;
* their features generally correspond to those of a particular tectonic environment, and this gives rise to the reconstitution of tectonic events;
* In certain well-defined cases, igneous rocks contain mineral deposits of great importance, such as uranium, tin and tungsten, which are usually associated with platinum, chromium and granites.
When classifying igneous rocks, one of the variables to take into account is their texture , which helps us to establish the description of their general appearance. While science recognizes more, there are six fundamental textures:
* vitreous : arise during certain volcanic eruptions after molten rock cools rapidly in the atmosphere;
* aphanitic : it is also called fine-grained and is characterized by having very small crystals that make it impossible to distinguish its minerals with the naked eye;
* phaneritic : for its formation it is necessary for the magma to cool slowly and at great depth;
* porphyritic : its crystals are large and are embedded in a paste of smaller ones;
* pegmatitic : the grain of these igneous rocks is very thick and the crystals that form it exceed one centimeter in diameter;
* pyroclastic : they resemble sedimentary rocks and are not made of crystals.