Wiktionary
n. (context geology English) one of the major groups of rock that makes up the crust of the Earth; consists of pre-existing rock mass in which new minerals or textures are formed at higher temperatures and greater pressures than those present on the Earth's surface
WordNet
n. rock altered by pressure and heat
Wikipedia
Metamorphic rocks arise from the transformation of existing rock types, in a process called metamorphism, which means "change in form". The original rock ( protolith) is subjected to heat (temperatures greater than 150 to 200 °C) and pressure (1500 bars), causing profound physical and/or chemical change. The protolith may be a sedimentary rock, an igneous rock or another older metamorphic rock.
Metamorphic rocks make up a large part of the Earth's crust and are classified by texture and by chemical and mineral assemblage ( metamorphic facies). They may be formed simply by being deep beneath the Earth's surface, subjected to high temperatures and the great pressure of the rock layers above it. They can form from tectonic processes such as continental collisions, which cause horizontal pressure, friction and distortion. They are also formed when rock is heated up by the intrusion of hot molten rock called magma 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 gneiss, slate, marble, schist, and quartzite.
Usage examples of "metamorphic rock".
The impact brecciation had created all kinds of useful metamorphic rock, and greenhouse-gas minerals were a common secondary find throughout the apron.
The impact brecciation had created all kinds of useful metamorphic rock, and green-house-gas minerals were a common secondary find throughout the apron.
The cuttings, screened from the mud as it flowed back into the sump pit, showed us still in the metamorphic rock.
They do have words for igneous rock, sedimentary rock, metamorphic rock, rock underfoot, rock dropping on your helmet from above, and rock which looked interesting and which they could have sworn they left here yesterday.
Granny Weatherwax, who lived in a cottage that was as olde-worlde as it was possible to be without being a lump of metamorphic rock, made no comment.
And Id have to bet that there wasnt a metamorphic rock within a thousand klicks of that site.
The quarter-mile-long mole was built of the same hard metamorphic rock as the castle's exterior walls, and was reckoned to have been blasted and lifted from the harbor basin in ancient times, either by the brute force and primitive ingenuity of multitudes, or by the laser lances and gravity sleds of visitors from outer space.
Beyond that bulwark of dark ceramic lay an unbroken rampart of metamorphic rock and eventually, the outer wall of the escarpment.