Upgrade of Java Quiz: Igneous Rocks 1
Igneous rocks form when magma (= molten rock material that has formed by partial melting of either crustal material or underlying mantle material or a combination of both) cools and solidifies. Two basic types are recognized. The intrusives are formed within the crust, while extrusives are formed on the crust during eruption of magma as lava flows or above the crust during ejection of tephra into the atmosphere. Their resulting textures reflects aspects of their cooling history.