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.
Topics:
1. Agents of metamorphic change
2. Classification: Foliated Textures, Non-foliated textures, and Composition
AGENTS OF METAMORPHIC CHANGE
• 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.