Metamorphism

Definition

Metamorphism is the process by which rocks undergo changes in mineralogy, texture, and chemical composition due to changes in temperature, pressure, and the presence of chemically active fluids. This process typically occurs deep within the Earth, often associated with tectonic activity, leading to the formation of metamorphic rocks from pre-existing igneous or sedimentary rocks.

5 Must Know Facts For Your Next Test

1. Metamorphism can be classified into two main types: regional metamorphism, which occurs over large areas under high pressure and temperature, and contact metamorphism, which occurs when rocks are heated by nearby molten magma.
2. The conditions of metamorphism are typically found at depths of several kilometers within the Earth's crust, where temperature and pressure increase significantly.
3. During metamorphism, minerals may recrystallize or alter chemically, leading to the development of new minerals that are stable under the new conditions.
4. Metamorphic rocks often display unique features such as foliation or banding due to the directional pressure experienced during their formation.
5. Metamorphism plays a critical role in the rock cycle, recycling materials and forming new rock types that can be exposed at the surface through erosion and tectonic uplift.

Review Questions

• How do temperature and pressure influence the process of metamorphism?
  • Temperature and pressure are crucial factors in metamorphism as they determine the physical and chemical environment in which rocks transform. Increased temperature can facilitate chemical reactions that lead to mineral changes, while increased pressure can cause minerals to realign or deform. The combination of these factors alters the original rock's composition and structure, resulting in metamorphic rocks that reflect these dynamic conditions.
• Discuss the differences between regional and contact metamorphism and provide examples of each.
  • Regional metamorphism occurs over large areas under high pressure and temperature, typically associated with tectonic forces such as mountain building. An example is the metamorphosis of shale into schist. In contrast, contact metamorphism happens when rocks are heated directly by nearby molten magma, leading to localized changes. An example would be limestone transforming into marble when subjected to heat from an intruding granite body.
• Evaluate the role of subduction zones in facilitating metamorphic processes and their impact on Earth's geology.
  • Subduction zones play a significant role in facilitating metamorphic processes due to the extreme pressures and temperatures encountered as one tectonic plate descends beneath another. This environment leads to intense deformation and chemical alteration of rocks, contributing to the formation of high-pressure metamorphic rocks such as eclogite. Additionally, the activity in subduction zones impacts Earth's geology by driving plate tectonics, causing earthquakes, and influencing volcanic activity, thus shaping the landscape over geological time scales.

Related terms

Metamorphic Rock: A type of rock that has been transformed from its original form through the process of metamorphism, resulting in changes in mineral composition and structure.

Foliation: The repetitive layering in metamorphic rocks that occurs due to the alignment of minerals under directed pressure.

Subduction Zone: An area where one tectonic plate is being forced below another, leading to intense pressure and temperature conditions that promote metamorphism.