The internal of the planet is hot. Geothermal Gradient: the heat within the planet steadily increases with depth; theheat is from radiation decay and remnant warmth of the Earth\"s formation.

Magma is molten absent material. As magma cools the facets within the magma combine and crystalize into minerals that kind an igneous rock.

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Magmacools either below the surface or in ~ the surface (magma that reaches the surface ar is dubbed lava).

As magma cools igneous rock is formed. There are two species of igneous rock:

1) Extrusive: magma reaches the surface of the Earth before cooling and the lava cools rapidly.

2) Intrusive: magma cools under the Earth\"s surface. The magma cools an extremely slowly.

As magma cools minerals are created into one interlocking setup prubraintv-jp.comcing an igneous rock.


As magma cools it undergoes reaction that type minerals. The price of cooling is really important. If the magma cools progressively then the reactions continue for a longer period of time and the result mineral crystals (grains) become large. If the magma cools promptly then the reactions are lot quicker and also the mineral crystals (grains) are smaller.

Igneous rocks will have a distinctive appearance (this is referred to as texture) based on the price of cooling (fast or slow).

Textural terms because that igneous rocks:

1. Phaneritic (coarse grained): rocks room composed the mineral grains large enough to be seen with the unaided eye. Indicitive of slow cooling, generally deep in ~ the Earth.


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Aphanitic (fine grained): rocks are composed the mineral grains too small to be checked out by the unaided eye. Indicitive of much faster cooling, normally at or close to the Earth\"s surface.

3. Glassy: magma cooled so quickly that crystal formation can not occur. Indicative of practically instant cooling in ~ the Earth\"s surface.

4. Porphorytic: large mineral cyrstals surrounding by a well grained procession (background). This texture develops when slow cooling starts to kind large mineral crystals. Prior to the magma is totally cooled the magma (and its huge mineral grains) moves closer to the surface and also finishes cooling at a an ext rapid pace.

Igneous rocks have actually a variety of chemical composition.

1. Sialic (granitic) or felsic: rocks have highest silica, contain feldspar and ferromagnesium minerals. Rocks room light in color.

2. Intermediate (andesitic): rocks have less silica, save on computer feldspar and also ferromagnesium minerals. Rocks are medium gray in color.

3. Mafic (basaltic): rocks have higher amounts of ferromagnesium minerals and also less silica and also feldspar. Rocks are dark in color, black or dark gray.

4. Ultramafic: highest amount that ferromagnesium minerals and least amount of silica. Rocks are usually a dark green to green-black.

Classification of Igneous Rocks

Igneous rocks are classified through both texture and also composition. Friend will find out to identify typical igneous rocks in lab.

intrusive (phaneritic)granitedioritegabbro
extrusive (aphanitic)rhyoliteandesitebasalt