This lesson introduces metamorphic rocks and the conditions that transform pre-existing rocks. Understanding metamorphism helps explain how rocks change deep within Earth and how some rocks found at the surface formed far below it.
Metamorphic rocks are one of the three major rock groups. Igneous rocks form when molten rock cools and solidifies. Sedimentary rocks form from deposited material or substances precipitated from water. Metamorphic rocks form when an existing rock is changed by heat, pressure, or chemically active fluids.
All flashcards
What is a metamorphic rock?
A rock formed when a pre-existing rock is physically or chemically transformed, mainly while remaining solid.
What does protolith mean?
The original rock that is changed during metamorphism. It may be igneous, sedimentary, or metamorphic.
How does contact metamorphism occur?
It occurs when heat from an intrusion of magma changes the surrounding solid country rock.
How can burial cause metamorphism?
Deep burial subjects rock to higher temperatures and pressure from the weight of overlying layers.
Why are metamorphic rocks useful to geologists?
Their minerals and textures can reveal the temperatures, pressures, and tectonic processes that occurred deep in Earth's crust.
Quiz questions
What does metasomatism describe?Answer: Chemical change in rock caused by fluids transporting substances into or out of it.
What can index minerals indicate in a metamorphic rock?Answer: Approximate pressure and temperature conditions during rock formation.
Which description best defines foliation in a metamorphic rock?Answer: A planar or banded arrangement of minerals, often produced by directed shortening.
Which sequence commonly represents increasing metamorphic grade in mudstone-derived rocks?Answer: Slate, phyllite, schist, then gneiss.
How can eclogite form in a subduction zone?Answer: Basalt in a descending slab can transform under high-pressure conditions.
Based on the Wikipedia article Metamorphic rock, licensed CC BY-SA 4.0. Adapted into a summary, flashcards and quizzes.