Metamorphic Rock
Chapter 10.4
Metamorphic Rock
1. Metamorphic Rock
a. Rock formed from other rocks as a result of
intense heat, pressure, or chemical processes.
b.Metamorphism is the changing of one type of rock
to another by heat, pressure, and chemical
processes.
c. Most metamorphic rock is formed deep beneath
the surface of the earth and consists of existing
igneous, sedimentary, or metamorphic rock.
Formation of Metamorphic Rock
2. Formation of Metamorphic Rock
a. Two types of metamorphism occur in the crust of
the earth. They are contact metamorphism and
regional metamorphism.
i. Contact metamorphism occurs when hot magma
pushes through existing rock and the heat from
the magma changes the structure and mineral
composition of the surrounding rock.
Formation of Metamorphic Rock
1. In this type of metamorphism only the rocks
near or touching the magma are changed by
its heat.
2. Hot chemical fluids working through
fractures may also cause changes in the
surrounding rock during contact
metamorphism.
Formation of Metamorphic Rock
ii. Regional metamorphism occurs over an area
of thousands of square kilometers during
periods of tectonic activity.
1. The movement of one tectonic plate against
another creates tremendous heat and
pressure in the rocks at the plate edges
which causes chemical changes in the
minerals of the rock.
2. Most metamorphic rock are created by this
type of metamorphosis.
Classification of Metamorphic Rocks
3. Classification of Metamorphic Rocks
a. Metamorphic rocks are classified by their
texture.
b.There are two types of textures a
metamorphic rock may have. They are
foliated and nonfoliated textures.
Classification of Metamorphic Rocks
i.Foliated rocks are formed with parallels
bands of minerals and can form in one of
two ways.
1.Extreme pressure may flatten the mineral
crystals in the original rock and push
them into parallel bands or…
2.Foliation can also occur when minerals
of different densities separate into bands,
producing a series of alternating dark and
light bands.
Classification of Metamorphic Rocks
ii. Examples of metamorphic rock with foliated
textures include slate, schist, and gneiss.
iii. Nonfoliated rocks are formed without mineral
bands.
1. Nonfoliated rocks are formed when heat
and pressure cause the mineral grains to
recrystallize so that the spaces between
them disappear.
a. Examples of nonfoliated rocks include
quartzite (original rock is sandstone) and
marble (original rock is limestone.)