Intursive and extursive rocks are two types of igneous rocks.Igneous rocks form when magma hardens underground.an example is the Obsidian . Obsidian rocksi s a dark-colored volcanic glass that forms from the very rapid cooling of molten rock material. It cools so rapidly that crystals do not form. A Basalt t(to the left) is a fine-grained, dark-colored extrusive igneous rock composed mainly of plagioclase and pyroxene. Extrusive rocks from when lava hardens.

Most metamorphism form when elevated tempertures & pressure and forms a few kilometers below earth's surface. The two basic type of metamorphic rocks are foliated metamorphic rocks and non-foliated metamorphic rocks. Foliated rocks are a layered or banded appearance that is produced by exposure to heat and directed pressure, and non-foilated do not have a layered or banded appearance.

Sedimentary rocks are formed by the accumulation of sediments. The three types of sedimentary rocks are clastic sedimentary rocks which are that are formed from mechanical weathering debris. Another sedimentary rock is chemical sedimentary rock which is forms when disolved materials precipitate from solution. The thrid one is organic sedimentary rocks forms from the accumulation of plant or animal debris.