FACTORS CONTROLLING METAMORPHISM ELS 11_12 Q1 0702 PS.pptx

FACTORS CONTROLLING METAMORPHISM ELS 11_12 Q1 0702 PS.pptx

1. Lesson 7. 2 Factors Controlling Metamorphism

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3. Describe the physical and chemical changes in rocks due to changes in pressure and temperature (metamorphism). At the end of this lesson, the given enrichment competency should be met by the students.

4. Explain how heat changes rocks. Describe how rocks behave under different types of stress. Explain how chemically active fluids affect rocks. Explain how a rock takes a long time to undergo metamorphosis.

5. Rocks do not just undergo metamorphism randomly. Most rocks that change are usually underground, and their degree of change may vary, depending on certain factors. What controls the change in rocks?

6. Procedure Each student must have one marshmallow and chocolate. Cut the top of the marshmallow and then place the chocolate on top of the marshmallow. Hold the spoon with your thumb inside the curved part. Press down on the chocolate, while it is on top of the marshmallow. Chocolate Marshmallow

7. Temperature It is affected by heat or thermal energy which triggers the chemical reaction to the rock, which can come from two sources: Igneous intrusions and Earth’s geothermal gradient. Thermometer is used to measure the degree of hotness and coldness of an object.

8. Two sources of thermal energy Intrusive bodies or plutons alter the texture and mineralogy of surrounding rocks to form metamorphic rocks The geothermal gradient of Earth is the rate of increase in temperature with increasing depth from the Earth’s surface. Temperature

9. Pressure Pressure increases with depth and can be classified into two types: uniform and differential stress. When minerals with spaces in their lattices are subjected to high amounts of pressure, the minerals collapse forming much denser crystals .

10. Pressure Confining pressure works by squeezing rocks together, dec r easing their volume. Uniform stress or hydrostatic stress refers to pressure with equal amounts of force coming from all directions.

11. Differential stress refers to the pressure that is unequal in different directions. Normal stress compresses objects from two opposing directions. Shear stress smears objects in the direction of the stress. Pressure Differential stress in a convergent boundary causes rocks to deform.

12. Chemically active fluids It enhances chemical reactions that alter the composition of rocks. Metasomatism is the change in the composition of a rock due to the addition or removal of substances or elements.

13. Time Metamorphism is a slow process that involves several processes. These processes are slow since metamorphic rock is formed with the protolith rock remaining in solid form. Metamorphic rocks that contain large crystals need time to form, on a scale of tens of millions of years.

14. The process of metamorphism is controlled by four factors: temperature, pressure, chemically active fluids, and time . Heat or thermal energy produced by an increase in temperature triggers chemical reactions which can cause recrystallization and/or neocrystallization. When minerals with spaces in their lattices are subjected to high amounts of pressure , the minerals collapse forming much denser crystals.

15. Chemical active fluid enhances chemical reactions which alter the composition of rocks. Metamorphism is a slow process that involves several other processes.

16. Metamorphism is a slow process. Heat is absorbed by intrusive bodies from rocks. Fluids only increase the size of rocks, but cannot alter the chemical composition of minerals. Rocks at higher temperatures and pressures crack easily. Uniform stress increases the volume of rocks. Write true if the statement is correct, and write false if otherwise.

17. Appalachian State University. “Classification of Metamorphic Rocks.” Accessed March 3, 2017. http://www.appstate.edu/~abbottrn/rck-id/mtmchrt.html Dictionary of Geology and Earth Science. 2013. Oxford University Press. Marshak, Steve. 2015. Earth: Portrait of a Planet. 5 th Edition. W.W. Norton & Company.Accessed March 3, 2017. http://www3.nd.edu/~cneal/PlanetEarth/Chapt-8-Marshak.pdf Nelson, Stephen A. 2015. Metamorphism and Metamorphic Rocks. Tulane University. Last Updated September 17, 2015. Accessed March 2, 2017. https://www.tulane.edu/~sanelson/eens1110/metamorphic.pdf Tarbuck, Edward J. and Lutgens, Frederick K. 2015. Earth Science . 14 th edition. Pearson Education Inc. USA. Tauxe, Lisa. “The Rock Cycle.” University of California, San Diego. Accessed May 7, 2018. https://topex.ucsd.edu/es10/lectures/lecture10/lecture10.html