Igneous Rock

Igneous Rock
Igneous (derived from the Latin word “ignis” meaning of fire), rocks are formed by the cooling and solidification of molten magma or lava at the surface of the crest (trap and basalt) or deep beneath the crest (granite). Majority of igneous rocks are smooth, crystalline and fine-grained. The Magma is formed by the melts of existing rocks in either a planet's mantle or crust. This magma maybe is from with or without crystalline.  It is estimated that igneous rocks make up 64.7% of the volume of the Earth's crust.
Maybe the melting is caused by the following reason:

• Increase in Temperature
• Decrease in Pressure
• Change in Composition

Classification of igneous rock
Igneous rocks are classified on the base of Chemical Composition, Texture, particle size, Mineralogy, and the Geometry of the Igneous body. All these formation of igneous rocks mostly depend on the cooling history, and the mineral composition.
Igneous rocks are further divide into two main categories:

Plutonic or Intrusive Igneous rock result when magma cools and crystallizes slowly underground the Earth's crust. It’s cool slowly, the result is intrusive igneous rock form have large mineral crystal. A common example of this type is granite, diorite, gabbro, pegmatite, and peridotite.


Volcanic or Extrusive Igneous rocks result from Magma reaching above or near the ground either as lava or fragmental and cool quickly then they are called Volcanic or Extrusive Igneous rocks. It’s cool quickly, the result, extrusive igneous rocks have small mineral crystals. A common example of this type is

Composition of Earth Crust

• It is estimated that igneous rocks make up 64.7% of the volume of the Earth's crust.
• Basalts and gabbros are 66% Of the earth crust.
• Granite are 16% Of the earth crust
• Granodiorites and diorites are 17%. Of the earth crust.
• Only 0.6% are syenites and 0.3% dunites and peridotites .
• The oceanic crust is 99% of basal which is in igneous rock.

.