Igneous Rocks are one of the major classifications of a rock. They form when any earth material melts and sedification of magma forms.  These rocks can form on  the outside of volcanoes and on rifts and ridges. Crystal sizes of igneous rocks determine on the cooling time it has.


Sedimentary Rocks are another one of the major classifications of a rock. They form when solids settle out of a fluid such as water or air. Most of these rocks are made up of pieces or clasts of other rocks. Sedimentary rocks form in a watery enviornment.                                                    


Metamorphic Rocks is the last major classification of a rock. They form when there is an increase of temperature and  pressure. If the rock melts it is not a metamorphic rock its reclassified as a sedimentary rock.