Aim: What are metamorphic rocks?

Chapter 4: section 3

Formation of Metamorphic Rocks

Metamorphic rocks are rocks that have been changed because of changes in temperature and pressure or due to the presence of hot watery fluids.

Metamorphic rocks may form from igneous, sedimentary rock, or other metamorphic rocks.

Example: granite gneiss

Gneiss

Heat and Pressure Rocks beneath the Earth’s surface are under great

pressure from the rocks above them.

Temperature will increase with depth in the Earth.

Underneath the Earth some minerals will melt or dissolve and recrystalize.

Example: Shale Slate phyllite schist gneiss

Each different type of metamorphic rock can come from multiple parent rocks.

Hot fluids Fluids can move through rock and

change the rocks composition.

Example: Water and carbon dioxide

What are fluids?

Classifying Metamorphic Rocks Texture and mineral composition determine how a

metamorphic rock is classified.• Foliated – layers• Nonfoliated – no layers

Physical properties of metamorphic rocks, such as the watertight nature of slate, make them useful for many purposes.

Classifying Metamorphic Rocks Foliated Rocks

• When mineral grains line up in parallel layers, the metamorphic rock is said to have foliated texture. Ex. Slate and gneiss

• Shale slate

• Shale: (minerals arrange into layers with heat and pressure.)

• Slate: Slate is watertight and easily split into layers• Uses: patio and pools

Classifying Metamorphic Rocks Nonfoliated rocks describe metamorphic

rock, such as quartzite or marble, whose mineral grains grow and grow but do not generally form layers.

Grains of quartz sandstone quartzite