The Rock Cycle
The rock cycle is the process by which rocks of one kind change into rocks of another kind. There are three main kinds of rocks: igneous rock, metamorphic rock, and sedimentary rock. Each of these rocks can change into the other kinds by one of these processes: cooling, melting, heat/pressure, weathering/erosion, and compacting/cementing (or squeezing tightly together). Two other substances also can become rocks and enter the rock cycle. They are magma which is liquid rock above or below ground, and sediment which is dust from crushed rock. First, the volcano erupts. Second, the lava cools down and turns into igneous rock. Third, the erosion of solid rock produces sediment. Fourth, the sediments slowly goes down to the ocean. Fifth, the sediment gets deposited. Sixth, because of the compaction and cementation, the sediments get squished down. Seventh, later the sediments turn into sedimentary rock. Eighth, because of all the heat and pressure, sedimentary rock turns into metamorphic rock and later the metamorphic rocks goes deep down underground and turns back to magma and the cycle starts over and over again!!!!!
http://simple.wikipedia.org/wiki/Rock_cycle