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Table of Contents
A metamorphic rock is a type of rock generated or formed from pre-existing sedimentary or igneous rocks due to changing environmental conditions. Environmental conditions can include changes in temperature, pressure, and mechanical stress, and the addition and subtraction of chemical components.
See the fact file below for more information on the metamorphic rock or alternatively, you can download our 23-page Metamorphic Rock worksheet pack to utilise within the classroom or home environment.
Key Facts & Information
ETYMOLOGY
- The word metamorphic comes from metamorphism, a Greek word that means “change in form”.
- Metamorphic rocks are made from igneous or sedimentary rocks that have changed their form or recrystallized as a result of changes in their physical environment.
- Metamorphism comprises changes both in mineralogy (the discipline that studies the physical properties, chemical composition, and internal crystal structure, of a mineral), and the components of the original rock.
HOW METAMORPHIC ROCKS ARE MADE
- The original rock transforms itself into a metamorphic rock in two ways.
- The alterations could be caused by the intrusion of magma into surrounding rocks of lower temperature, or due to large-scale tectonic movements of the Earth’s lithosphere, the layer of the Earth that comprises the crust and the upper mantle, where tectonic plates are found.
- These tectonic plates collide and produce friction. Metamorphic rocks are generated by the extreme heat produced by these movements.
MINERALS IN METAMORPHIC ROCKS
- Metamorphic minerals are formed only at high temperatures and pressures due to the process of metamorphism, the change of minerals or geologic texture in pre-existing rocks.
- The minerals in metamorphic rock are known as index minerals, such as biotite, chlorite, sillimanite, kyanite, staurolite, andalusite, and some garnet.
- The original rock of a metamorphic rock is called a protolith, and an index mineral used to determine the degree of metamorphism a protolith has undergone.
- Depending on the index mineral found in a metamorphic rock, geologists can determine the minimum pressure and heat the protolith has experienced, as certain minerals are only formed at certain pressures and temperatures.
- The higher the pressure and temperature in which the rock formed, the higher the grade of the rock.
- There are other minerals found in metamorphic rocks that are not formed as a result of metamorphism, like olivines, pyroxenes, amphiboles, micas, feldspars, and quartz.
- Furthermore, these minerals formed during the crystallization of igneous rocks.
- Crystallization can be a natural or artificial process by which atoms or molecules in solid forms are highly organized into a structure known as a crystal.
- The process of crystallization naturally occurs in igneous rocks. The minerals formed in this process could still remain once the igneous rock undergo metamorphism.
- The physical aspect of the rock changes during metamorphism, like how the particles of a rock become bigger due to the process of recrystallization.
- Recrystallization only occurs during metamorphism—when temperature and pressure reorganize the atoms of a mineral by diffusion or dislocation glide.
- When a rock is recrystallized, the mineral composition may remain unchanged.
- To simply illustrate the process of recrystallization, observe how snow recrystallizes into ice.
- To further illustrate, calcite crystals found in limestone and chalk, when they undergo metamorphism and recrystallization, change into marble, a larger metamorphic rock.
FOLIATION
- Metamorphic rocks form layers in the process of foliation.
- The term foliation is derived from the Latin term folia which means leaves.
- Foliation happens when a rock is being shortened along one axis or direction during recrystallization.
- The elongated crystals of minerals become rotated such that their long axes are perpendicular to the orientation of shortening which leads to a platy structure.
- As a result, a banded or foliated rock is formed.
- The bands represent the minerals that formed these rocks.
TYPES OF METAMORPHISM
- CONTACT METAMORPHISM
- Contact metamorphism occurs when magma is injected into the surrounding solid rock or country rock.
- The changes take place wherever the magma comes into contact with the rock since the temperature is highest in this point.
- A metamorphosed zone around igneous rock that forms from the cooling magma is called a contact metamorphism aureole.
- REGIONAL METAMORPHISM
- Regional metamorphism is also known as dynamic metamorphism. It occurs when rock changes over a wide area.
- This happens when rocks are located below the Earth’s surface, since they are subjected to high temperatures and great pressure from the rock layers above.
- Because of this position, the majority of the lower continental crust is metamorphic.
- The metamorphosed rocks under the Earth’s surface are later exposed due to uplifting and erosion, and the action of surface processes such as water flow or wind.
Metamorphic Rock Worksheets
This is a fantastic bundle which includes everything you need to know about the metamorphic rock across 23 in-depth pages. These are ready-to-use Metamorphic Rock worksheets that are perfect for teaching students about a metamorphic rock which is a type of rock generated or formed from pre-existing sedimentary or igneous rocks due to changing environmental conditions. Environmental conditions can include changes in temperature, pressure, and mechanical stress, and the addition and subtraction of chemical components.
Complete List Of Included Worksheets
- Metamorphic Rock Facts
- Quick Questions
- Choosing Adjectives
- Vocabulary Completion
- Process of Metamorphism
- Index Mineral Search
- Fill in the Blanks
- Rock Illustrations
- Look and Learn
- Catchy Tune
- Learning Summary
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Link will appear as Metamorphic Rock Facts & Worksheets: https://kidskonnect.com - KidsKonnect, October 8, 2019
Use With Any Curriculum
These worksheets have been specifically designed for use with any international curriculum. You can use these worksheets as-is, or edit them using Google Slides to make them more specific to your own student ability levels and curriculum standards.