Metamorphism
Topic: Minerals, Rocks and the Rock Cycle · NCERT: Class 11, Ch 5 "Geomorphic Processes"
Meaning
Metamorphism (meta = change, morph = form) is the change in a rock's minerals and texture without the rock melting. It happens when pressure, volume and temperature (PVT) change. Mountain building, earthquakes and plate movements, or contact with hot magma, can all cause such changes. Minerals may recrystallise (form new crystals) or line up in layers. Metamorphic rock can form from igneous, sedimentary or older metamorphic rock. It is usually harder and more compact than the rock it came from.
Example
Limestone near Makrana in Nagaur district, Rajasthan, was changed into marble, which was used to build the Taj Mahal. The Narmada also cuts through marble at Bhedaghat, near Jabalpur, Madhya Pradesh.
Don't confuse with
- Melting: if a rock melts, it becomes magma, and when that magma cools it forms igneous rock. Metamorphism stops just short of melting, so the rock stays solid throughout.