• Comes from the Greek words ‘meta’ which means to ‘change’ and
‘morphe’ which means ‘form’
• Key idea is that the rock changes form remaining solid
• Requires both high pressure and temperature

• A rock layer is placed under higher pressure and temperature than it was previously
• This forces the minerals inside to shift to a more stable state
• Remember Bowen’s Reaction Series?

• Two main defined types:
• Foliated : has layers and/or bands of minerals, which were formed due to the high pressures that the rock was place under
• Non-foliated : has blocky crystal shapes, with no true defined layering

• Metamorphic rocks are defined by ‘grade’ which is, in turn, defined by how much pressure and temperature the rock was placed in.
• Low Grade : rock was placed under low pressure and temperature
• High Grade : rock was placed under high pressure and temperature

• Regional: occurs when large areas are affected by increased pressure and temperature
• Contact : occurs around an inclusion, where the increased P and T result in the host rock experiencing limited metamorphism around the inclusion
• Hydrothermal : involves rocks and infusions of very hot water, like around a thermal vent

• Construction: marble and slate are both commonly used in construction projects and have been for thousands of years
• Metal ores: hydrothermal metamorphism will sometimes produce purer metallic ores, such as a well separated gold ore found in quartz

• Rock formation is cyclical
• As rocks form, they are slowly worn down and made into sediments, which are reformed into rock, which is then put under further pressure and formed into rock again.
• Weathering plays a key part of this cycle, along with pressure and temperature