Rocks

Ingneous rock

The word 'ingneous' is from Latin which means fire.This material may have been //lava// erupted at the Earth's surface, or //magma// (unerupted lava) at shallow depths, or magma in deep bodies. Rock formed of lava is called //extrusive//, rock from shallow magma is called //intrusive// and rock from deep magma is called putonic. There are many kinds of ingneous rock, but the two best known rocks are basalt and granite. Basalt is the dark, fine-grained stuff of many lava flows and magma intrusions. Its dark minerals are rich in magnesium (Mg) and iron (Fe), hence basalt is called a //mafic// rock. So basalt is mafic and either extrusive or intrusive. Granite is the light, coarse-grained rock formed at depth and exposed after deep erosion. It is rich in feldspar and quartz (silica) and hence is called a felsic rock. So granite is felsic and plutonic. <<<< Picture of igneous rock.

Sedimentary rock Sedimentary rocks are the second great rock class. Whereas igneous rocks are born hot, sedimentary rocks are born cool at the Earth's surface, mostly under water. They usually consist of layers or //strata//, hence they are also called stratified rocks. Depending on what they're made of, sedimentary rocks fall into one of three types. The most common type of sedimentary rocks is clastic sedimentary rocks, it consist of the granular materials that occur in sediment: mud and sand and gravel and clay. Sediment mostly consists of surface minerals— quartz and clays — that are made by the physical breakdown and chemical alteration of rocks.Second one is chemical sedimentary rock.Last one is organic sedimentary rock. <<<<< Picture of sedimentary rock Metamorphic Rocks Metamorpihic rock is another type of rocks. Metamorphic rocks are rocks that have changed form due to heat and pressure. Metamorphic comes from the Greek words meta and morph. Meta means change and morph means form. So we get metamorphic meaning to change form. There are two kinds of metamorphic rocks.One is contact metamorphism, and the other is Regional metamorphism. Contact metamorphism occurs when magma intrudes or forces its way into existing rock. The heat of the magma bakes the surrounding rocks causing them to change. This is a local event. The changes due to contact metamorphism are relatively small and are said to be low-grade metamorphism. An example of contact metamorphism is the metamorphic rock marble. Marble is created from limestone that has been subjected to heat. Regional metamophism by contrast takes place over large areas and is high-grade metamorphism. Regional metamorphism is associated with mountain building. The causes or agemts of metamorphism are heat, pressure, and hydrothermal solution. <<<<<<< Picture of metamorphic rock
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