IGNEOUS ROCKS

DEFINITION Igneous rocks are formed out of hot larva or magma. The extruded larva on solidification over the earth’s surface gives rise to extrusive igneous rock. The magma on solidification below the earth’s surface is called intrusive rock.

MOLTEN MAGMA

INTRUSIVE AN EXTRUSIVE IGNEOUS ROCKS

INTRUSIVE IGNEOUS ROCK The molten magma under the earth’s surface gets solidify there itself to form the intrusive igneous rock. It has high pressure and temperature. it cools slowly Also known as plutonic rock. Granite

EXTRUSIVE IGNEOUS ROCK When the molten magma goes out as volcano and then solidify is known as extrusive igneous rock. It cools relatively fast. It has high temperature and pressure. Rhyolite

COMPLEX IGNEOUS ROCK These rocks cools at the intermediate level that is not above or below the earths surface. Basalt

INTRUSIVE ROCK CONCODANT DISCORDANT

SILLS When the magma solidifies as a thin sheets or layers is called sills.

PHACOLITS When the magma is under low pressure it will not exert much pressure to make space for itself.

LACOLITS When the magma gets intruded into the layer due to high viscosity it may not spread eventually forming domes.

DYKES When the magma moves vertically hence forming a wall like structure is known as dykes.

VOLCANIC NECKS The magma gets solidified in the inactive volcanic areas in the form of thick pipes is called volcanic necks.

BATHOLITHS When the magma moving under high pressure forming huge mass of igneous rock.

STRUCTURE OF IGNEOUS ROCK primary secondary

PRIMARY STRUCTURE Flow structure Pillow structure Blocky and ropy structure Spherulitic structure Orbicular structure Rift and grain structure Tension joints Vesicular structure Miarolitic structure

USES Granites posses excellent qualities of building rocks for structural as well as architectural purposes. They have high crushing strength. Has least porosity. Used in decorative purposes. Could get in variety of colours.

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