Rocks

Igneous, sedimentary & metamorphic rocks

Igneous , Sedimentary, Metamorphic are rocks changed by magma or magma that changes into those rocks. There are there are three kinds of rocks Igneous Sedimentary, Metamorphic.

The first rock is called igneous. igneous are formed when rock (magma) cools and solidifies, with or without crystallization, either below the surface. This magma can be derived from partial melts of pre-existing rocks in either the earths mantle or crust. Typically, the melting is caused by one or more of the following proceses. an increase in temprature a decrease in pressure, or a change in composition. Over 700 types of igneous rocks have been described, most of them formed beneath the surface of the Earth's crust.

Igneous rocks make up approximately ninety five percent of the upper part of the Earth's crust. Igneous are important because their minerals and chemistry give information about the compisition of the earths mantle. their features are usually characteristic of a specific tectonic environment. in some special circumstances they host important mineral deposits like tungsten uranium and tin.

There are also two more kinds of igneous rocks there is intrusive and extrusive. Intrusive igneous rocks are formed from magma that cools and solidifies within the earth. Surrounded by pre-existing rock. the magma cools slowly The mineral grains in such rocks can generally be identified with the naked eye. intrusive rocks can also be classified according to the shape and size of the body and other formations into which it intrudes. And Extrusive igneous rocks are formed at the Earth's surface as a result of the partial melting of rocks within the mantle and crust.

Now for sedimentary. Sedimentary rocks are formed because of the over as particles of sendiment are deposited out of air, ice, or water flows carrying the particles in suspionn. As sediment deposition builds up, the overburden pressure squeezes the sediment into layered solids in a process known as lithifacation or rock formation and the original connate fluids are expelled. The term diegeness is used to describe all the chemical, physical, and biological changes and during and after its lithification, exclusive of surface weathering. Sedimentary rocks are laid down in layers called beds. Each new layer is laid down horizontally over older ones. There are usually some gaps in the sequence called unconformities. These represent periods in which no new sediments were being laid down, or when earlier sedimentary layers were raised above sea level and eroded away.

Sedimentary rocks contain important information about the history of earth They contain fossils, the preserved remains of ancient plants and animals. The composition of sediments provides us with clues as to the original rock. Sedimentary rocks can contain fossils because, unlike most igneous and metamorphic rocks, they form at temperatures and pressures that do not

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