Metamorphic Rocks

Tilted Gneiss Outcrop near Namib desert
Metamorphosis means a profound change in form, structure or substance from one stage to the next in the life history of an object or living organism.  Therefore, metamorphic rocks originate from a change in form and structure from pre-existing igneous, sedimentary or metamorphic rocks.  The key is understanding that a  significant change has undergone in the rock's structure.  This change is caused by intense heat and pressure to the rock material.  The change sometimes takes place deep within the Earth.  However, unlike igneous rocks, metamorphic rocks do not undergo melting. 

During metamorphism, structures, such as layering, may become distorted and new minerals may form, or crystals may grow.  If enough heat and pressure is applied to the rock, metamorphism often results in the alignment of crystals called foliation. 






Alignment of minerals called banding due to heat and pressure


  






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