Rocks and Their Cycle
The rock cycle starts out as magma, and it goes through many transformations and becomes many different types of rock.
The rock cycle starts as magma under the ground, or in some cases lava on the surface, and it cools and crystallizes to become an igneous rock. Igneous rocks are classified by their origin, texture, or what it feels like, and mineral content. Two very different igneous rocks are basalt and granite. Granite was formed from magma, and basalt was formed from lava. Granite is coarse-grained, or has varied crystal sizes and colors,and basalt is fine-grained, or has small crystals. Basalt is dark and granite is light. Both of them are good for tools, with granite being used for building and basalt for gravel.
Igneous rocks can either become metamorphic rock or sediments. They become sediments, or tiny pieces of rock and crystals, when weathering and erosion wear away the rock. Those sediments then get compacted, or pressed together, with other sediments, and cemented, or glued together by dissolved minerals, to become sedimentary rock. The 3 main types of sedimentary rocks are clastic, organic and chemical. Most Sedimentary rocks are clastic, or made from broken pieces of other rocks. Some clastic rocks are shale and sandstone. Some sedimentary rocks are organic, or made from fossils from plants and animals, like coal. Very few are chemical rocks, or made from dissolved minerals, including limestone. Sedimentary rocks make great building materials because they are soft enough to cut into slabs.
Igneous rocks and sedimentary rocks can both become metamorphic rocks when it goes down near the mantle and heat and pressure changes its appearance, texture, crystal structure and mineral content. The reason they go down is that collisions between plates push the rock down towards the hot mantle, and the deeper it is in the crust, the more pressure on that rock. Geologists classify metamorphic rocks by the arrangement of grains that make up the rocks. Some are foliated, or have their grains arranged in parallel bands or layers. A common foliated rock is slate, which was originally the sedimentary rock shale, but is more dense and compact. Others are nonfoliated, or have randomly arranged grains, like marble and quartzite, which were originally limestone and sandstone, respectively. Two of the most useful metamorphic rocks are marble and slate, because marble makes a great building material, for example the Taj Mahal, and slate is good for things like floors and roofs.
The rock cycle ends and then starts again when metamorphic rock melts into magma or lava, and it stays like that for a long time. Magma or lava then becomes igneous rock again, and it starts all over again.
The rock cycle is natures way of recycling. Every day, rock is being transformed into new types of rock. Its amazing that a rock has been through so much. Rocks can be used for many things, and when your done with them they become something else. The rock cycle has a very important job!!!!!!