Metamorphic Rocks

Contact Metamorphism -- the basalt flow has baked the underlying limestone

You may wish to print a copy of the lecture outline (minus the illustrations) and you have two options:

• Microsoft Word if you use that Word Processor or
• A Netscape Document that you can print (use the Left Arrow key to return to this page).
• Or, you may view the Metamorphic Rocks power point presentation shown in class.

Course Objectives

After reading Chapter Seven, you should be able to:
1. Define metamorphism.
2. List and describe the agents of metamorphism.
3. Describe the textures of metamorphic rocks.
4. List the most common metamorphic rocks and how they are classified.
5. Describe the three environments of metamorphism.
6. Explain the relationship between metamorphism and plate tectonics.

Introduction

Metamorphic rocks are "changed rocks". A mineral assemblage stable at low temperatures and pressures may not be stable at elevated temperatures and pressures. As temperature and/or pressure increases "old minerals" may change (typically they increase in size) or new minerals may form. In this image a basalt (on the top) has "baked" the underlying, older limestone. The baking is confined to the top 6" of the limestone.

Class Notes

Internet Resources

1. An Introduction to Metamorphic Rocks

   "Metamorphic rocks form from other rocks (protolith) by essentially solid-state changes in mineralogy and/or texture as a result of a change in chemical and/or physical environment.

   "Metamorphism takes place in a variety of geologic settings. A general outline of metamorphic settings is shown below. It should be noted that with the exception of impact metamorphism, the general types grade into one another."

2. Plate Tectonics and the Rock Cycle

   "James Hutton (1727-1797), the eminent 18th century gentleman farmer and founder of modern geoscience, authored the concept of the rock cycle, which depicts the interrelationships between igneous, sedimentary, and metamorphic rocks. The upper part of the earth (mantle, crust and surface) can be envisioned as a giant recycling machine; matter that makes up rocks is neither created nor destroyed, but is redistributed and transformed from one rock type to another. PETROLOGY, the study of rocks and their origins, is essentially the formal process by which we resolve the interrelationships expressed in the rock cycle."

A Virtual Field Trip to Big Bend National Park

This site was selected for this chapter as it provides a relatively comprehensive analysis of the geology of this fascinating area. In particular, read the sections on the three major rock types and see how that information is incorporated into the geologic history of the region.

This site was constructed by two students at Texas A&M University.

" The Big Bend Virtual Field Trip was created for an independent study project for the Texas A&M University Department of Geology under the supervision of Dr. Bruce Herbert. During the week of Spring Break 1996, we visited Big Bend. for the purpose of researching the geology of the park and taking pictures of pertinent geologic features. Once all of the pictures and information were compiled, we scanned the images and started construction of the web site.Big Bend for the purpose of researching the geology of the park and taking pictures of pertinent geologic features. Once all of the pictures and information were compiled, we scanned the images and started construction of the web site."

Learning about geology from a computer screen is only half as fun as enjoying it in the field!

Self-Quiz

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Copyright by John C. Butler, July 29, 1995