Igneous rocks were named after the Greek word for ‘fire’.Igneous rocks form when molten lava from the Earth’s crust cools down, crystallizes, and solidifies. There exist two types of igneous rocks called extrusive rocks and intrusive rocks.Magma refers to the molten material that remains extant in two forms, either wholly fluid or semi-fluid, and rests within or below the crust of the Earth. Made of the atoms and molecules of melted minerals, and it is when this magma cools and the atoms and molecules of these minerals regroup, forming mineral grains, that igneous rocks and lava, if above surface, are formed. To form the igneous rock, magma is key, for it is the cooling, crystallization, and solidification of the lava flow that results in the creation of this ‘magmatic’ rock. Depending upon whether the molten material cools above or below the earth’s surface, the igneous rock is further classified as an extrusive igneous rock or an intrusive igneous rock. Granite, pumice, basalt, and obsidian are excellent examples of igneous rock. Out of these, Granite is the most common. Today, the world has explored around 700 kinds of igneous rock.Fun fact, the Earth’s moon, that glittering orb of celestial radiance, is also made of igneous rocks.If you enjoy this article, you can also read about the Alabama state rock and space rocks.Extrusive Igneous RocksExtrusive igneous rocks are also known as ‘volcanic rocks’.When the lava flow gushes onto the Earth’s surface, it morphs into extrusive rocks. The lava could either seep onto the surface of the Earth directly or it could rain down molten rock material through a massive explosion of lava that we know as a volcanic eruption. In the latter case, the fragments of the molten explosion are called pyroclastic. Therefore, an extrusive igneous rock is that igneous rock which is formed upon the surface of the Earth instead of beneath it, the surface is where it splatters, cools, crystallizes, and solidifies. The obsidian and the basalt rock are fine examples of the extrusive igneous rock category. The obsidian, a natural volcanic glass, hued in the shades of the darkest night, is formed when the erupted magma cools quickly without extreme crystal growth. Basalt is another extrusive rock that has a black glassy appearance and is hard in structure. The basalt rock is what the topmost layer of the ocean floor is made of. Pumice is yet another solid rock that results from the molten activity above the Earth’s surface, and is the lightest rock on Earth.Intrusive Igneous RocksIntrusive igneous rock is also known as plutonic rock.When igneous rocks are formed beneath the surface of the Earth, they come to be known as intrusive rocks. The intrusive igneous rock takes about a million years to form since that is how long it takes for the magma to cool down beneath the surface of the Earth. The intrusive rock is also able enough to form huge bodies, and when it does, it is called a batholith. Batholiths form when magma races its way to the core of the Earth, and that is where it cools down, then proceeds to crystallize, before solidifying and resulting in rocks, a process that may take many millennia. A solid example of an intrusive rock is Granite. Because of its strong nature, granite is used in the construction of statues and gravestones. The intrusive granite rocks have also proven to be highly durable, thereby contributing to their favored reputation. Diorite and pegmatite are two other examples of intrusive igneous rocks.The Rock CycleThe rock cycle depicts the transition of the three prime kinds of rocks through geological time. This key trinity is made of sedimentary rocks, igneous rocks, and metamorphic rocks, each of which is a consequence of varying physical changes.Through a series of physical changes, one kind of rock can be changed into another. The most important of these physical processes are crystallization, erosion and sedimentation, and finally metamorphism. It all begins with magma. This molten lava cools either below the surface of the earth or above it and is the key ingredient to the formation of igneous rocks. This cooling results in different crystals experiencing varying temperatures, thereby undergoing the process of crystallization. Slow cooling results in the formation of larger crystals, while fast cooling gives birth to smaller ones. Erosion and sedimentation happen when these crystals are picked up by water bodies or the wind and carried elsewhere to be deposited in the form of sediments. These sediments keep collecting together, forming a larger mass that, if and when compacted closely and cemented together, forms a sedimentary rock. Then comes metamorphism, a process that occurs when a rock remains exposed to an extreme rate of heat and pressure but holds strong instead of melting. It is because of metamorphism that the texture and composition of minerals of a rock change.Thus, in this way, each of these prime rocks can change into the other through a series of physical processes.Formation Of Igneous RocksIgneous rocks stem from the Earth’s crust that remains blanketed by hot magma. The process of how igneous rock is formed is quite simple, for all it needs is for molten lava to cool down.Magma is either entirely or partially molten rock material and is found tickling the Earth where its crust rests. This molten rock material is formed from the remnants of the rocks that were extant before. The sizzling hot lava flow races for the Earth’s surface. During this blazing journey, the magma undergoes certain changes as a consequence of temperature and pressure influences caused as it rises. As a result of these alterations, the lava cools down gradually. Then, the calmer lava crystallizes, its dazzling motion slowing. Lastly, because the lava cools and crystallizes, it also solidifies fully from its original state of mobility. Depending upon where the lava cools down, igneous rocks branch out into two types, extrusive igneous rocks, and intrusive igneous rocks. Thus, the Igneous rock is created through a simple three staged recipe, molten lava being the key ingredient.Here at Kidadl, we have carefully created lots of interesting family-friendly facts for everyone to enjoy! If you liked our suggestions for Igneous rocks facts then why not take a look at what do metamorphic rocks look like, or 3 types of metamorphic rock.
Igneous rocks were named after the Greek word for ‘fire’.
