Metamorphic Rocks
In this lesson, we are going to take a look at how metamorphic rocks form. Metamorphic rocks are the unlucky rocks of the world because they got to their current state after being tortured by intense heat and pressure. In fact, if we look at the word metamorphism, we see that it comes from the word 'morph,' which means to be transformed or changed. So, metamorphic rocks are previously formed rocks that have been transformed by exposure to heat and/or pressure.
Influencing Factors
So, we already discussed two influencing factors that can transform pre-existing rocks into metamorphic rocks, which are heat and pressure. And, as you can image, it takes very intense heat and pressure to make rock change its form. In fact, the heat needed to make this change often comes from magma, which is the extremely hot fluid that forms below the surface of the Earth that you likely associate with volcanoes.
The pressure involved in metamorphism may come from the rock being deeply buried and this creates such intense pressure that crystals within the rock can grow together or collapse and rearrange into new mineral crystals. We also see that metamorphic rocks may be influenced by a third factor: the chemically active fluids that circulate around the newly forming rock and introduce different ions, which cause new and different mineral crystals to grow.
Metamorphic Processes: Recrystallization
There are different metamorphic processes that are responsible for the changes that we see in these rocks. Recrystallization is the most common and is defined as the metamorphic process by which crystals are packed together creating a new crystal structure. Recrystallization requires a lot of heat and pressure, and the process changes the mineral's size and shape, yet the basic composition remains unchanged.
For example, limestone can go through the process of recrystallization to turn into marble. Limestone contains tiny calcite crystals that come from shells of marine creatures that were broken down and compacted into the sedimentary rock. When that limestone is buried and subjected to intense forces, the microscopic crystals pack together and slowly morph into the larger crystals of calcite that we find in marble. The same marble that you might use as a countertop in your kitchen.
Metamorphic RocksIn this lesson, we are going to take a look at how metamorphic rocks form. Metamorphic rocks are the unlucky rocks of the world because they got to their current state after being tortured by intense heat and pressure. In fact, if we look at the word metamorphism, we see that it comes from the word 'morph,' which means to be transformed or changed. So, metamorphic rocks are previously formed rocks that have been transformed by exposure to heat and/or pressure.Influencing FactorsSo, we already discussed two influencing factors that can transform pre-existing rocks into metamorphic rocks, which are heat and pressure. And, as you can image, it takes very intense heat and pressure to make rock change its form. In fact, the heat needed to make this change often comes from magma, which is the extremely hot fluid that forms below the surface of the Earth that you likely associate with volcanoes.The pressure involved in metamorphism may come from the rock being deeply buried and this creates such intense pressure that crystals within the rock can grow together or collapse and rearrange into new mineral crystals. We also see that metamorphic rocks may be influenced by a third factor: the chemically active fluids that circulate around the newly forming rock and introduce different ions, which cause new and different mineral crystals to grow.Metamorphic Processes: RecrystallizationThere are different metamorphic processes that are responsible for the changes that we see in these rocks. Recrystallization is the most common and is defined as the metamorphic process by which crystals are packed together creating a new crystal structure. Recrystallization requires a lot of heat and pressure, and the process changes the mineral's size and shape, yet the basic composition remains unchanged.
For example, limestone can go through the process of recrystallization to turn into marble. Limestone contains tiny calcite crystals that come from shells of marine creatures that were broken down and compacted into the sedimentary rock. When that limestone is buried and subjected to intense forces, the microscopic crystals pack together and slowly morph into the larger crystals of calcite that we find in marble. The same marble that you might use as a countertop in your kitchen.
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