Metamorphic rock

Metamorphic rocks arise from the transformation of existing <a href="/facts/Rock_(geology)/FXCJkmop">rock</a> to new types of rock in a process called <a href="/facts/Metamorphism/8eWHgy6K">metamorphism</a>. The original rock (<a href="/facts/Protolith/72uzWogN">protolith</a>) is subjected to temperatures greater than 150 to 200 °C (300 to 400 °F) and, often, elevated pressure of 100 <a href="/facts/Pascal_(unit)/Am1To2Qm">megapascals</a> (1,000 <a href="/facts/Bar_(unit)/wwFWTTkT">bar</a>) or more, causing profound physical or chemical changes. During this process, the rock remains mostly in the solid state, but gradually recrystallizes to a new texture or mineral composition. The protolith may be an <a href="/facts/Igneous_rock/xeMJhUah">igneous</a>, <a href="/facts/Sedimentary_rock/HQDCjrco">sedimentary</a>, or existing metamorphic rock.
Metamorphic rocks make up a large part of the <a href="/facts/Earth%2527s_crust/VSy2u31r">Earth's crust</a> and form 12% of the Earth's land surface. They are classified by their protolith, their <a href="/facts/Chemical/EWcXU41d">chemical</a> and <a href="/facts/Mineral/LkUFbNmv">mineral</a> makeup, and their <a href="/facts/Rock_microstructure/rsR0CG11">texture</a>. They may be formed simply by being deeply buried beneath the Earth's surface, where they are subject to high temperatures and the great pressure of the rock layers above. They can also form from <a href="/facts/Plate_tectonics/RtRG5lY4">tectonic</a> processes such as continental collisions, which cause horizontal pressure, friction, and distortion. Metamorphic rock can be formed locally when rock is heated by the <a href="/facts/Intrusion_(geology)/Wl6xaY1a">intrusion</a> of hot molten rock called <a href="/facts/Magma/hRotHju9">magma</a> from the Earth's interior. The study of metamorphic rocks (now exposed at the Earth's surface following erosion and uplift) provides information about the temperatures and pressures that occur at great depths within the Earth's crust.
Some examples of metamorphic rocks are <a href="/facts/Gneiss/rUJYgBHu">gneiss</a>, <a href="/facts/Slate/hSVHL6Lj">slate</a>, <a href="/facts/Marble/5JEFb0qu">marble</a>, <a href="/facts/Schist/jHBjtEQw">schist</a>, and <a href="/facts/Quartzite/8rNpCMrv">quartzite</a>. Slate and quartzite tiles are used in building construction. Marble is also prized for building construction and as a medium for sculpture. On the other hand, schist <a href="/facts/Bedrock/mn9WCgtX">bedrock</a> can pose a challenge for <a href="/facts/Civil_engineering/avh5kEq2">civil engineering</a> because of its pronounced planes of weakness.

Metamorphic rock open-in-new

Metamorphic rock