Metamorphic Rocks 101

What is a metamorphic rock?

To understand metamorphic rocks you must first know what metamorphism is. Metamorphism is the changing of one rock into another rock. Metamorphism occurs under the influence of extreme heat, pressure, and/or chemical fluids. A rock undergoing metamorphism changes the texture and mineral composition of the rock but never leaves solid form. If the rock were to melt and be changed that would classify it as an Igneous rock. Metamorphic rocks are transformed through the solid state.

How many types of metamorphism are there?

There are four types of metamorphism. Contact metamorphism is a result of heat generated from a nearby magma source. Regional metamorphism consists of change through intense heat and pressure. Hydrothermal metamorphism is a chemical change that occurs when hot fluids circulate through out the rock. Finally, fault zone metamorphism is change that happens along fault lines.

What features are present in metamorphic rocks?

When looking at metamorphic rocks things to look for include Foliation and the type of foliation present. Foliation types include; rock cleavage, schistosity, gneiss, and non-foliated. Metamorphic rocks are broken down into two groups based on whether the rock is foliated or non-foliated.

Can any rock be changed into a metamorphic rock?

Yes, any rock can be transformed into a metamorphic rock. In fact the parent rock (the original rock) is very important in the metamorphic process. The parent rocks makeup determines what metamorphic agent will change the rock. Some common parent child match ups in rock include; Slate and Shale, and Marble and Limestone.

Where does metamorphism occur?

Metamorphism really occurs wherever the three agents; heat, pressure, and chemical fluids; are present. Commonly though metamorphism occurs along convergent plate boundaries and subduction zones. Also hydrothermal metamorphism occurs along the mid-ocean ridge.

Metamorphic Rock Flow Chart

Metamorphic Rock Flow Chart