19 Facts About Igneous rocks

Igneous rocks rock is formed through the cooling and solidification of magma or lava.

Igneous rocks occur in a wide range of geological settings: shields, platforms, orogens, basins, large igneous provinces, extended crust and oceanic crust.

Intrusive igneous rocks make up the majority of igneous rocks and are formed from magma that cools and solidifies within the crust of a planet.

Hypabyssal Igneous rocks are less common than plutonic or volcanic Igneous rocks and often form dikes, sills, laccoliths, lopoliths, or phacoliths.

Volcanic rocks are mostly fine-grained or glassy, it is much more difficult to distinguish between the different types of extrusive igneous rocks than between different types of intrusive igneous rocks.

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Igneous rocks are classified according to mode of occurrence, texture, mineralogy, chemical composition, and the geometry of the igneous body.

Classification of the many types of igneous rocks can provide important information about the conditions under which they formed.

Two important variables used for the classification of igneous rocks are particle size, which largely depends on the cooling history, and the mineral composition of the rock.

Igneous rocks that have crystals large enough to be seen by the naked eye are called phaneritic; those with crystals too small to be seen are called aphanitic.

Igneous rocks are classified on the basis of texture and composition.

The texture of volcanic Igneous rocks, including the size, shape, orientation, and distribution of mineral grains and the intergrain relationships, will determine whether the rock is termed a tuff, a pyroclastic lava or a simple lava.

Plutonic Igneous rocks tend to be less texturally varied and less prone to showing distinctive structural fabrics.

The chemistry of igneous rocks is expressed differently for major and minor elements and for trace elements.

Tholeiitic magma series rocks are found, for example, at mid-ocean ridges, back-arc basins, oceanic islands formed by hotspots, island arcs and continental large igneous provinces.

Much of the early classification of igneous rocks was based on the geological age and occurrence of the rocks.

However, in 1902, the American petrologists Charles Whitman Cross, Joseph P Iddings, Louis V Pirsson, and Henry Stephens Washington proposed that all existing classifications of igneous rocks should be discarded and replaced by a "quantitative" classification based on chemical analysis.

The continental crust is composed primarily of sedimentary rocks resting on a crystalline basement formed of a great variety of metamorphic and igneous rocks, including granulite and granite.

Volcanic Igneous rocks are named after Vulcan, the Roman name for the god of fire.

Intrusive Igneous rocks are called "plutonic" Igneous rocks, named after Pluto, the Roman god of the underworld.