Transcript Metamorphic Rock - Nova Scotia Department of Education

Metamorphic Rock

The changes or alterations of rock in
terms of texture or mineralogy from the
pre-existing rock is caused by:
◦ Temperature
◦ Pressure
◦ Chemical environment changes
Metamorphism

Another factor that affects the
metamorphism is the original or parent
rock.

There are numerous combinations of
metamorphic rocks.

The first characteristic is to look at the
texture of the rock:
◦ Foliated
◦ Non-foliated
Classification of Metamorphic Rock

The alignment of minerals in a rock
subjected to increased pressure is called
foliation..

This involves rocks with two or more
crystals.
Foliation
Pressure will cause
the material to
compact.
The type of pressure
will dictate the
alignment of the
minerals; foliation.
Pressure Effects

The type of minerals will determine the
type of new rock formed.

If only one mineral is found in the parent
rock, when it undergoes metamorphism
the composition remains the same but the
crystals grow larger.

More that one mineral present, recrystallization can take place making for
new minerals.
Mineralogy

The two main types are:
◦ Contact metamorphism, and
◦ Regional metamorphism.
Types of Metamorphism

These rocks are formed during
metamorphism usually without significant
differential stress but with high
temperature.

Contact metamorphism occurs in country
rock (rock surrounding the magma)
immediately adjacent to intruded
magmas.
Contact Metamorphism

This is the most common source of
metamorphic rock of the Earth’s crust.

It involves occurring at great depths.

Pressure, temperature and the chemical
environment of the original rock are all
altered.
Regional Metamorphism

This is the term given to the intensity of
metamorphism that a mineral has been
subjected.

Lots of heat, pressure and chemical
change it would be considered a high
metamorphic grade.
Metamorphic Grade
Shock Metamorphism

The impact of meteors can create a
metamorphism called Shock
metamorphism.

As the meteor strikes the earth it creates
enough heat and melts local rock which
are thrown up to 100km from the impact
site. These rocks are called Tektites.