Metamorphic rock

Definition

Metamorphic rock is a type of rock that has been transformed from an existing rock type through heat, pressure, and chemically active fluids. This transformation process alters the mineral composition and structure of the rock, leading to new textures and features, such as foliation or banding. Understanding metamorphic rocks is essential for grasping how they fit into the broader rock cycle and the dynamics of Earth's internal structure.

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 the alignment of minerals.
2. Common examples of metamorphic rocks include schist, gneiss, marble, and quartzite, each originating from specific parent rock types.
3. The conditions under which metamorphic rocks form vary widely, with low-grade metamorphism occurring at lower temperatures and pressures, while high-grade metamorphism occurs under extreme conditions.
4. Metamorphic rocks can provide valuable information about the tectonic forces and geological history of an area due to their formation in response to specific environmental conditions.
5. Many metamorphic rocks are economically important as they can be sources of minerals such as talc, slate, and marble, used in construction and manufacturing.

Review Questions

• How do metamorphic rocks contribute to our understanding of the rock cycle?
  • Metamorphic rocks play a crucial role in the rock cycle by illustrating the processes that alter existing rock types. They form from igneous or sedimentary rocks when subjected to heat and pressure over long periods. This transformation showcases how rocks can change state within the cycle, highlighting the dynamic nature of Earth's geology and the interrelationships among different rock types.
• What are the primary factors that lead to the formation of metamorphic rocks, and how do these factors interact within Earth's internal structure?
  • The formation of metamorphic rocks is primarily driven by heat, pressure, and chemically active fluids. Heat can come from nearby magma or deep burial beneath Earth’s surface, while pressure results from tectonic forces compressing rocks. These factors interact with the mineral content of the original rock, altering its structure and composition. This process is essential in understanding the internal dynamics of Earth’s crust, as it reveals how tectonic activity can influence mineral transformations.
• Evaluate the significance of foliation in metamorphic rocks regarding geological history and tectonic activity.
  • Foliation in metamorphic rocks is significant because it indicates the directional pressure that influenced their formation during tectonic events. The alignment of minerals in a foliated rock reveals information about the stress conditions present when it was formed. Analyzing foliation can help geologists reconstruct past tectonic movements and understand regional geological histories. This insight contributes to broader knowledge about plate tectonics and Earth's evolving landscape over geological time.

Related terms

Igneous Rock: Igneous rock forms from the cooling and solidification of molten material, either magma or lava, and is categorized into intrusive and extrusive types.

Sedimentary Rock: Sedimentary rock is formed through the accumulation and compaction of mineral and organic particles, often laid down in layers over time.

Metamorphism:

Metamorphism is the process by which existing rocks are subjected to extreme heat and pressure, resulting in physical and chemical changes that create metamorphic rocks.