Rock Topics

Metamorphic Rocks

Metamorphic comes from the Latin words for changed form, and refers to rocks that formed by changing pre-existing rocks with heat, pressure, or chemical activity that occurs under conditions of heat and pressure.  Metamorphic rocks are classified based on their texture and composition. 


1. Agents of metamorphic change

2. Classification: Foliated Textures, Non-foliated textures, and Composition

3. Common metamorphic rocks


• The range of temperatures at which metamorphic activity takes place is between 300 and 1470 degrees Fahrenheit.  Heat sources include magma, geothermal heat, and friction along faults.

• Pressure sources include the weight of overlying rocks deep in the earth.  Shear pressure in fault zones can metamorphose rocks at shallower depths.

• Chemical activity is usually caused by water at higher temperatures and pressures.  Water acts to dissolve pre-existing rocks, to transport dissolved materials, and to catalyze chemical changes.

to change the rate of chemical reactions