- Formation of metamorphic rocks
- Contact and regional metamorphism
- Uses of metamorphic rocks
- Describe how metamorphic rocks are formed.
- Describe the properties of some common metamorphic rocks.
- Relate some common uses of metamorphic rocks.
contact metamorphism: Changes in rock due to heating by contact with hot magma.
foliation: Formation of layers in rock due to extreme pressure.
regional metamorphism: Changes in rock over a large area due to pressure from other rock.
stable: State of minerals in rock after metamorphism.
Introducing the Lesson
Introduce metamorphic rock with the excellent animation of metamorphism at the URL below. Point out how heat and pressure turn sedimentary and igneous rocks into metamorphic rocks. Tell students they will learn more about metamorphic rocks in this lesson.
Discuss the causes of metamorphism. Explain how magma causes high temperatures in contact metamorphism and how masses of rock cause great pressure in regional metamorphism. Make sure students know that high temperatures and great pressure often occur together and affect the same rock. Point out that the extreme temperatures that cause metamorphism do not melt rocks completely.
Question: If the rocks melted completely and then new rocks formed, what type of rocks would they be?
Sample answer: They would be igneous rocks, or rocks that form when minerals crystallize from melted rock.
Have pairs of students make a Venn diagram that compares and contrasts contact and regional polymorphism. Make sure they understand that extreme heat causes contact metamorphism, and extreme pressure (often with heat) causes regional polymorphism.
Ask one or more students to create a Web page about a specific example of metamorphism, such as limestone changing to marble when exposed to high temperatures (contact metamorphism). Suggest that they describe, and use photos to illustrate, the two types of rocks, and also list some of their important uses. Encourage other students to visit the Web page.
Use the inquiry activity “Metamorphic Sandwiches” (see URL below) so students can model the processes of metamorphism. Discuss how the processes they apply to their “metamorphic sandwiches” relate to the high pressures and temperatures that cause metamorphism in rocks.
Students may think incorrectly that foliated metamorphic rocks are sedimentary rocks, because the foliated rocks appear to have layers like the depositional layers of sediments. Ask them to explain the different causes of the layers in the two types of rocks. Correct any misconceptions that their explanations reveal.
Reinforce and Review
Copy and distribute the lesson worksheets in the CK-12 Earth Science for Middle School Workbook. Ask students to complete the worksheets alone or in pairs to reinforce lesson content.
Lesson Review Questions
Have students answer the Review Questions listed at the end of the lesson in the FlexBook® student edition.
Check students’ mastery of the lesson with Lesson 4.4 Quiz in CK-12 Earth Science for Middle School Quizzes and Tests.
Points to Consider
What type of plate boundary would produce the most intense metamorphism of rock?
Do you think new minerals could form when an existing rock is metamorphosed?