Magma is molten rock material below and within the earth’s crust. Magma that reaches the earths surface is called lava.

When magma solidifies, igneous rock is formed. The characteristics of the resulting rock depends on the magma’s viscosity, density, composition, and temperature of the magma.

Igneous rocks can be formed below the surface and are called either intrusive or plutonic. Or they can be formed on the surface and are called extrusive or volcanic.

Some intrusive igneous rocks are Granite, Diorite, Gabbro, Peridotite. Some Extrusive rocks are Rhyolite, Andesite, Basalt, Komatiite. 

Igneous Links

Rock Hounds
Igneous Rocks --
Kinds of Igneous Rocks
Igneous Rocks -- Wikipedia
Lesson: Igneous Rocks
Igneous rocks -- Britannica
Igneous Rocks
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