Contact Metamorphism Vs. Regional Metamorphism: Definition & Differences

Lesson Transcript
Instructor: Rebecca Gillaspy

Dr. Gillaspy has taught health science at University of Phoenix and Ashford University and has a degree from Palmer College of Chiropractic.

Contact metamorphism is where minerals and texture are changed as rock encounters lava, whereas regional metamorphism is where this process occurs over large areas. Understand the definitions and learn the differences and features involved in these metamorphic processes. Updated: 09/28/2021


If you ever roasted a marshmallow over a hot campfire and ended up with a lump of something black and charred, rather than something gooey and delicious, what you actually did was performed a mini-experiment in contact metamorphism. Of course with true contact metamorphism we are using heat to change rocks, not marshmallows. In this lesson, we will learn more about contact metamorphism and how it differs from regional metamorphism, which relies more on pressure to cause rock minerals to change.

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  • 0:07 Metamorphism
  • 0:37 Metamorphic Rocks
  • 1:15 Contact Metamorphism
  • 2:29 Regional Metamorphism
  • 3:48 Lesson Summary
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Metamorphic Rocks

Now, before we go too far into our terminology, it's important to understand that when geologists are talking about something going through a process of metamorphism, they are most likely talking about metamorphic rocks. These rocks are kind of neat because they were previously-formed rocks that have been transformed by exposure to heat and/or pressure into new rocks. So, at one time these rocks may have been igneous, sedimentary or even other metamorphic rocks, but due to forces placed upon them they were transformed, or metamorphosed, into different rocks.

Contact Metamorphism

Now, as we mentioned earlier, there are two types of metamorphism: contact metamorphism and regional metamorphism. Let's start by discussing contact metamorphism, which is the one we introduced with the marshmallow experiment. Contact metamorphism is a type of metamorphism where rock minerals and texture are changed, mainly by heat, due to contact with magma. This is an easy name to recall if you remember that these rocks change by actually coming in contact with something very hot, like magma.

Image you were looking at a cross-section of the Earth where you can see the Earth's surface, as well as some deep layers of rock underground. Now imagine that an intrusion of hot liquid magma forces its way up through these deep layers of rock. The magma bakes the surrounding rocks causing them to change, or metamorphose. So all around the outer boundary of the intrusion of magma you will have the formation of metamorphic rocks. Now, keep in mind that because there is a somewhat direct contact with the heat source, contact metamorphism takes place over a relatively small area.

Regional Metamorphism

It is a different story for our second type of metamorphism: regional metamorphism. This is a type of metamorphism where rock minerals and texture are changed by heat and pressure over a wide area or region. This name is also fairly easy to recall if you remember that regional metamorphism takes place over a wide region.

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