Structure of Igneous Rock

Flow Structure - parallel band or streaks which is caused by flow of magma or lava during cooling and crytallization.

Forms of Igneous Bodies

Extrusive igneous bodies – form when magma pours out on the surface of the earth crust.

Intrusive igneous bodies – form when magma consolidates at some depth below the earth crust. Such rock bodies show variation in size and shape. Ex. Batholith, stock, dyke & sill.

Discordant bodies – those rock which cuts through the overlaying strata. Ex. Batholith, stock, dyke.

Concordant bodies – those rock which lie between rocks bed. They do not show transgressive relation to the rock they invade. Ex. Sills, lopoliths and laccoliths.