METAMORPHIC ROCKS. Formation and Characteristics. Rocks are formed on Earth as igneous, sedimentary, or metamorphic rocks. Igneous rocks form when rocks are heated to the melting point which forms magma.
Formation and Characteristics
The word "metamorphic" comes from Greek and means "To Change Form".
that cause an increase inPRESSURE
that cause an increase inHEAT
from the core
Solid rock can be changed into a new rock by stresses
The descending of rock layers at subduction zones causes metamorphism in two ways:
There are 3 factors that cause an increase in pressure which also causes the formation of metamorphic rocks. These factors are:
Metamormorphism can be instantaneous as in the shearing of rocks at plate boundaries.
There are 2 main ways that metamorphic rocks can form. These are: Contact and Regional metamorphism.
Silt and clay can become deposited and compressed into the sedimentary rock shale. The layers of shale can become buried deeper and deeper by the process of deposition.
Garnet-mica schist – microscopic view
In this specimen of coarse-grained biotite schist you can see clearly the flakes of dark mica, lined up parallel to each other, and separated by light-coloured material, which is mostly millimetre-sized quartz crystals. In the photo above you see the thin edges of the mica flakes.
PARENT ROCK - sedimentary
LOW-GRADE METAMORPHIC ROCK
MEDIUM-GRADE METAMORPHIC ROCK
METAMORPHIC ROCKS - review