rocks
The rock cycle is very important to us because it explains the way the different types of rocks are formed on earth. Geologists classify rocks in three groups, depending on the Earth processes that made them. Some rocks are formed by heat and pressure. Other rocks are formed by weathering and erosion. The three rock groups are igneous, sedimentary, and metamorphic rocks. Igneous rocks are formed from melted rock that has cooled and solidified. They can form underground or above ground. Underground, they are formed when the melted rock, called magma, deep within the earth becomes trapped in small pockets. As these pockets of magma cool slowly underground, the magma becomes igneous rocks. Igneous rocks also form when volcanoes erupt, causing the magma to rise above the earths surface, above the earths surface magma is called lava. The rocks are formed as the lava cools. Sedimentary rocks are formed at the surface of the Earth, either in water or on land. They are layers of fragments of rocks, minerals, or animal or plant material. Most sedimentary rocks become cemented together by minerals. Weathering is anything that breaks the rocks into smaller pieces or sediments. This can happen by the forces of like wind, rain, and freezing water.The sediments are carried to other places by the wind or running water. The larger heavier pieces settle out first. The smallest fragments travel farther and settle out last. This is called deposition.Compaction occurs after the sediments have been deposited. The weight of the sediments squeezes the particles together. Cementation happens as dissolved minerals become deposited in the spaces between the sediments. These minerals act as glue or cement to bind the sediments together. Metamorphic rocks are formed from other rocks. When the rocks under go heat and pressure they form metamorphic rocks. This rock can be a igneous rock, a sedimentary rock or even another metamorphic rock.