Rocks are all around us! They cover the Earth, various shades, sizes, and shapes! They help us to develop new technologies and are used in our everyday lives. Our use of rocks includes as building material, cosmetics, cars, roads, and appliances. Rocks play a valuable role in natural systems such as providing habitat like the cliffs at Grand Canyon National Park where endangered condors nest, or provide soil nutrients in Redwood where the tallest trees in the world grow.

Like most Earth materials, rocks are created and destroyed in cycles. The rock cycle is a model that describes the formation, breakdown, and reformation of a rock as a result of sedimentary, igneous, and metamorphic processes. All rocks are made up of minerals. A mineral is defined as a naturally occurring, crystalline solid of definite chemical composition and a characteristic crystal structure. A rock is any naturally formed, nonliving, firm, and coherent aggregate mass of solid matter that constitutes part of a planet.

Rocks change as a result of natural processes that are taking place all the time. Most changes happen very slowly. Rocks deep within the Earth are right now becoming other types of rocks. Rocks at the surface are lying in place before they are next exposed to a process that will change them. Even at the surface, we may not notice the changes. The rock cycle has no beginning or end.

The next page will show a representative of the Rock Cycle with numbers regarding the 'steps' and the rocks/mineral that are involved.

Type of Rocks.

Not all rocks are the same!

Now, it comes to discussing the main part of the Rock Cycle, the rocks! The three main types of rocks, or classes, of rocks are Sedimentary, Metamorphic, and Igneous. The differences among them have to do with the way these rocks are formed.

Sedimentary

Sedimentary rocks are formed from particles of sand, shells, pebbles, and other fragments of material. Together, all these particles are called sediment. Gradually, the sediment accumulates in layers and over a long period of time hardens into rock. Generally, sedimentary rock is fairly soft and may break apart or crumble easily. You can often see sand, pebbles, or stones in the rock, and it is usually the only type that contains fossils.