Metamorphic rock

Definition

Metamorphic rock is a type of rock that has undergone a transformation due to extreme heat, pressure, or chemically active fluids, changing its mineral composition and structure. This process, known as metamorphism, can occur deep within the Earth's crust where tectonic plates interact. Metamorphic rocks provide insight into the geological processes that shape our planet and reveal information about the conditions present during their formation.

5 Must Know Facts For Your Next Test

1. Metamorphic rocks are classified into two main types: foliated and non-foliated, based on their texture and alignment of minerals.
2. Common examples of metamorphic rocks include schist, gneiss, marble, and quartzite, each formed under specific conditions of pressure and temperature.
3. The formation of metamorphic rocks is often associated with tectonic activity, such as continental collision or subduction zones, where significant heat and pressure are generated.
4. Metamorphic rocks can provide valuable information about the history of geological processes, including past tectonic events and environmental changes.
5. Regional metamorphism occurs over large areas due to tectonic forces, while contact metamorphism happens when rocks are heated by nearby molten magma or lava.

Review Questions

• How do metamorphic rocks differ from igneous and sedimentary rocks in terms of formation processes?
  • Metamorphic rocks are formed from pre-existing rocks that undergo changes due to high heat and pressure or chemical processes, while igneous rocks are created from the cooling and solidification of magma or lava. Sedimentary rocks, on the other hand, form from the accumulation and compaction of mineral particles and organic materials. The key difference lies in how each type of rock is created: metamorphic rocks evolve from existing rocks under specific conditions, igneous rocks result from molten material cooling, and sedimentary rocks originate from surface processes.
• Discuss the role of tectonic activity in the formation of metamorphic rocks.
  • Tectonic activity plays a crucial role in the formation of metamorphic rocks by creating conditions of extreme heat and pressure. When tectonic plates collide or move apart, they can generate significant forces that alter existing rock formations. This process can lead to regional metamorphism over large areas or contact metamorphism when magma intrudes into surrounding rocks. The interaction between tectonic forces and geological materials ultimately leads to the transformation that characterizes metamorphic rocks.
• Evaluate the importance of studying metamorphic rocks in understanding Earth's geological history.
  • Studying metamorphic rocks is vital for piecing together Earth's geological history because they serve as records of past environmental conditions and tectonic events. Through analysis of their mineral compositions and textures, scientists can infer the temperature and pressure conditions present during their formation. Additionally, metamorphic rocks often indicate significant geological processes such as mountain building and continental collision. By understanding these processes, researchers can better grasp how Earth's surface has evolved over time and how it continues to change.

Related terms

Igneous rock:

Rock formed through the cooling and solidification of magma or lava, representing one of the primary types of rock in the rock cycle.

Sedimentary rock: Rock that forms from the accumulation and compaction of mineral and organic particles, typically found at the Earth's surface and providing evidence of past environments.

Metamorphism: The process by which existing rocks are altered in mineralogy, texture, and chemical composition due to changes in temperature and pressure.