key term - Metamorphism

Definition

Metamorphism is the process by which rocks undergo changes in mineral composition and texture due to exposure to heat, pressure, and chemically active fluids. This process transforms existing rocks, primarily igneous and sedimentary, into metamorphic rocks, contributing significantly to the rock cycle and the formation of mountain ranges. Metamorphism is crucial for understanding how different rock types evolve over geological time and how continental formations are shaped by tectonic forces.

5 Must Know Facts For Your Next Test

1. Metamorphism can result from various factors including tectonic plate movements, which generate heat and pressure deep within the Earth’s crust.
2. The intensity of metamorphism can vary widely, from low-grade metamorphism at lower temperatures and pressures to high-grade metamorphism at extreme conditions.
3. Foliation is a common texture developed during metamorphism where minerals align perpendicular to the direction of applied pressure, often seen in schist and gneiss.
4. Metamorphic rocks can contain unique features like porphyroblasts, which are large crystals formed during metamorphism, indicating the conditions under which the rock was altered.
5. Metamorphism plays a significant role in the rock cycle by recycling existing rocks and contributing to the formation of new geological structures in mountain ranges.

Review Questions

• How does metamorphism contribute to the transformation of rocks within the rock cycle?
  • Metamorphism contributes to the rock cycle by transforming pre-existing rocks, such as igneous or sedimentary types, into metamorphic rocks through heat and pressure. This transformation can change the mineral composition and texture of the original rock, creating new materials that can eventually be uplifted or exposed at the Earth's surface. As these new metamorphic rocks weather away, they can also contribute sediments that may form new sedimentary rocks, completing the cycle.
• Discuss how regional metamorphism is related to mountain-building processes.
  • Regional metamorphism is closely associated with mountain-building processes that occur during tectonic plate collisions. When two continental plates converge, immense pressure and temperature are generated over vast areas, leading to extensive metamorphic changes in surrounding rocks. This results in the formation of large mountain ranges and the development of foliated metamorphic rocks like schist and gneiss, which provide evidence of the intense conditions present during their formation.
• Evaluate the role of metamorphism in shaping continental formations and its significance in understanding Earth's geological history.
  • Metamorphism plays a critical role in shaping continental formations by altering existing rock structures under varying conditions of temperature and pressure during tectonic activity. These metamorphic processes not only create new geological features but also preserve records of past environmental conditions and tectonic events. Understanding these transformations helps geologists reconstruct Earth's geological history, including how continents have evolved over time through processes like subduction, collision, and rifting.

Related terms

Metamorphic Rock:

A type of rock that has been changed from its original form through the processes of metamorphism, resulting in new mineral assemblages and textures.

Regional Metamorphism: A type of metamorphism that occurs over large areas under high pressure and temperature conditions, often associated with mountain-building events.

Contact Metamorphism:

A localized metamorphic process that occurs when rocks are heated by proximity to molten magma or lava, leading to changes in mineralogy without significant pressure.