IGNEOUS ROCKS Meaning and
Definition
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Igneous rocks are a type of rock that is formed from the cooling and solidification of molten magma or lava. These rocks can be found both on the Earth's surface and in the Earth's crust. The term "igneous" is derived from the Latin word "ignis," meaning fire, as these rocks are formed by the intense heat of volcanic activity.
The formation of igneous rocks begins deep within the Earth, where the intense heat and pressure cause the melting of rocks. This molten material, known as magma, slowly rises to the surface through volcanic activity or cools and solidifies within the Earth's crust. When magma is erupted onto the Earth's surface, it is referred to as lava, which then cools and solidifies rapidly due to exposure to air or water.
One of the defining characteristics of igneous rocks is their crystalline nature. As the magma or lava cools, mineral crystals begin to form within the rock. The size and arrangement of these crystals are determined by the rate of cooling; slower cooling results in larger crystals, while rapid cooling results in finer-grained rocks.
Igneous rocks can be further classified into two main types: intrusive and extrusive. Intrusive igneous rocks cool and solidify slowly beneath the Earth's surface, resulting in coarse-grained rocks such as granite. Extrusive igneous rocks, on the other hand, cool rapidly on the Earth's surface or in shallow depths, resulting in fine-grained rocks such as basalt. These rocks play a significant role in Earth's geology and are essential in understanding the planet's history and processes.
Etymology of IGNEOUS ROCKS
The word "igneous" comes from the Latin word "ignis", meaning "fire". The term "igneous rocks" was first proposed by the Scottish geologist James Hutton in the late 18th century. Hutton used this term to describe rocks formed from molten lava or magma that had cooled and solidified.
