Ignis

Molten rock that is found beneath the earth’s body.

O Sometimes, an igneous rocks shows parallel or sub parallel bands or streaks w/c are caused by the flow of magma or lava during cooling and crystallization.

O This is characterized by the development of bulbous, overlapping, pillow like structure in the body of igneous mass. It is typical structure of rock formed from mobile basaltic lava.

O Structural variation developed in the volcanic rocks due to different mobility. Highly viscous “dry” lava undergo very little movement after their eruption and before cooling. Their surface show broken and movement after their eruption

O Most lava contains large amounts of gas and volatiles. These gas and volatiles escape into the atmosphere when they solidify on the earth’s surface. As a result of this, numerous gas cavities are formed near tops of lava flows. These gas cavities are called the “vesicles” and the volcanic rock contains “vesicles” and the volcanic rock contains structure

Divisional planes which are found in all kinds of igneous rock impressed upon them by force acting from outside.

Typically two-mineral aggregates (mainly quartz and feldspar), formed by initial spherulitic growth of one mineral and later crystallization of a second mineral from the liquid or glass between the fibers.

With uniform cooling and contraction in a homogenous magma, the parting planes tend to:

) is an uncommon plutonic rock type which is usually granitic in composition.

O These rocks cool rapidly or very near the Earth’s surface. o The rapid cooling is due to the great difference in temperature between the hot molten rock and the relatively cool surrounding environment o Fined-grained rocks

O These rocks cool slowly with the Earth’s crust o The slow cooling enables minerals to grow large o The texture of these rocks are coarse gained

Derived from words feldspar and silica. o Igneous rocks enriched in silica (SiO2) and silicates rich in Al, K, and Na (e.g. feldspar) are called felsic. o These rocks are characteristics of the continental crust (e.g. granite).

O Roughly even mixtures of felsic minerals (mainly plagioclase) and mafic minerals (mainly hornblende, pyroxene, and/or biotite).

O Igneous rocks with a high proportion of silicates rich in Mg and Fe

Rocks composed of large proportion of silicate of Mg and Fe