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metamorphic rock

Primary Information
Secondary Information

Definition

Metamorphic rock is a type of rock that has been changed by heat and pressure. It is formed when existing rocks are buried deep underground and subjected to high temperatures and pressures.

The heat and pressure cause the minerals in the rock to recrystallize, which changes the rock's texture and properties. Metamorphic rocks can be formed from any type of rock, including sedimentary rocks, igneous rocks, and other metamorphic rocks.

The type of metamorphic rock that is formed depends on the type of rock that is being changed, the temperature and pressure it is subjected to, and the amount of time it is subjected to these conditions.

Some common metamorphic rocks include:

  • Slate: This rock is formed from shale. It is characterised by its smooth, flat surface and its ability to be easily split into thin sheets.
  • Gneiss: This rock is formed from granite. It is characterised by its banded appearance.
  • Marble: This rock is formed from limestone. It is characterised by its smooth, polished surface and its white colour.
  • Metamorphic rocks are an important part of our world. They are used to make everything from countertops to buildings to jewellery.

How can the word be used?

The metamorphic rocks in this area were formed by the collision of two tectonic plates.

metamorphic rock

Different forms of the word

Noun: A rock that has been changed from its original form by heat and pressure.

Adjective: Relating to or made of metamorphic rock.

Verb: To change (a rock) into metamorphic rock.

Etymology

The word "metamorphic rock" comes from the Greek words "meta" (change) and "morphē" (form). The word "metamorphic" was first used in English in the 17th century.

Question

What is metamorphic rock?

AQA Science Exam Question and Answer

Question:

Explain the formation of metamorphic rock and discuss the processes that lead to its distinct characteristics. Provide examples of common types of metamorphic rock and explain how they differ from other rock types.

Answer:

Metamorphic rock is formed through the transformation of pre-existing rocks, either igneous, sedimentary, or other metamorphic rocks, due to changes in temperature, pressure, and chemical conditions. These changes occur deep within the Earth's crust.

The processes involved in metamorphism include heat, pressure, and the presence of chemically active fluids. Heat and pressure cause the minerals in the original rock to recrystallize, creating new mineral alignments and textures. This can result in the development of foliation, where minerals align in parallel layers, giving the rock a striped appearance.

Common types of metamorphic rock include marble, formed from limestone, and slate, derived from shale. Marble's recrystallization of calcite gives it a smooth, polished appearance, making it suitable for sculptures and architecture. Slate's foliation, stemming from fine clay particles, makes it ideal for roofing due to its durability and resistance to water.

Metamorphic rocks differ from igneous and sedimentary rocks primarily in their formation process. While igneous rocks crystallize from molten material, and sedimentary rocks are formed from accumulated sediments, metamorphic rocks undergo a change from existing rocks without melting.

Understanding the metamorphic process and resulting rock types helps geologists decipher Earth's geological history and the dynamic forces shaping its surface over millions of years.