Department of Earth Science |Northeastern Illinois University

ESCI 121
Spring 2007

Review for Exam #2  (February 29, 2007)                                                                        Dr. Sanders

For Exam #2, you should be able to do the following:

Common Sedimentary Rock-Forming Minerals

* Examine  and describe the properties of each mineral sample in the following groups, and determine what each group has in common.  Finally, assign a name to each mineral using a mineral key. 
First Group:   7, 17, 19, 20, 40, 43     Second Group:  2, 18, 30, 46          Third Group:  14, 33, 34, 44

Sedimentary Rocks

* Using the list of common sedimentary rock-forming minerals that appears above (you should have assigned names to each of the numbered specimens listed above), tell how each is likely to play a part in forming a sedimentary rock.

Describe, give examples of, and explain the importance of each of the following processes in forming sediments and sedimentary rocks:
        weathering               chemical weathering        mechanical (physical) weathering
        sediments                chemical sediments          detrital (clastic) sediments                                                
  dissolution              precipitation                        transport                 
        deposition               lithification        

* List the four main processes that transport sediment.
* Using the sedimentary rock key in your textbook on p. 63, examine, describe, classify, and name a variety of hand samples of sedimentary rocks.  Please note: on the key, you may delete/ignore the following rocks: breccia, siltstone, and travertine.  Also, please substitute the word "clay" for "mud" on the detrital rocks side.  Samples we looked at in class were the following:   #103, 104, 109, 113, 118, 128, 129, 135, 145, 151, 153, 158

Explain how detrital (clastic) sedimentary rocks form, list names of rocks of this group, and give the grain size of sediments that make up each rock.  Tell how you might recognize each of these rocks when you see it again.

* Explain how chemical sedimentary rocks form, list a few names of rocks of this group, and tell what minerals make up each rock.  Tell how you might recognize each of the rocks when you see them again.

Common Igneous Rock-Forming Minerals

* Examine  and describe the properties of each mineral sample listed below.  Assign a name to each mineral using a mineral key.  Check back later for some mineral numbers.

Igneous Rocks

* Sketch a melting curve on a graph with axes showing temperature and pressure.  Show on which sides of the curve liquids and solids would exist.

* Use the melting curve you sketched to illustrate the three processes that lead to melting of rock material:
       - thermal melting (increasing heat)
       - decompression melting (reducing pressure)
       - shifting the position of the melting curve by introducing volatiles (i.e., water)

* On the graph, sketch another curve, for a rock material that melts at a higher temperature.  Label the two curves to show which one illustrates  melting of silica-rich material, and which one illustrates melting of silica-poor material.

* Describe the three general settings in which volcanoes are found in the world, and for each, use the melting curve to explain how/why magma forms in that setting:
       - divergent plate boundaries
       - subduction zones
       - hot spots

* Explain the relationship between cooling rate and crystal size in an igneous rock.

* Using the hand samples of igneous rocks in a rock box,  tell which of them cooled relatively slowly, quickly, or instantaneously.

* Explain the difference between rocks of a granitic (felsic) composition and those of basaltic (mafic) composition, and show how to recognize each type in a hand sample.

* Describe the unique characteristics, including crystal size, composition,  and cooling rate, of each of the following igneous rocks:
               - granite         - gabbro       - rhyolite         - basalt       - pumice        - obsidian

* Describe the three main shapes/profiles of volcanoes, and explain why they are different and how each is related to the volcano's eruptive style.

* Describe and explain the connections between a volcano's location and plate tectonic setting, types of tectonic plates involved, mineralogic composition of the magma (felsic, mafic, intermediate), volcano shape/profile (cinder cone/dome, composite cone/stratovolcano, shield), volcano eruptive style, silica content of the magma, melting temperature of the rock material (higher/lower), and the material erupted from the volcano (e.g. gas, pyroclastics, lava).

Describe the composition of continental and oceanic plates in terms of felsic / mafic mineralogy. 

Metamorphic Rocks

* Describe the three agents of metamorphism (heat, pressure. and chemically active fluids) and explain the changes they can bring about in a rock.

* Describe the plate tectonic settings in which metamorphic rocks form.

* Explain what foliation is, tell what causes it, and give examples of three foliated metamorphic rocks.

* Describe and give the names of three non-foliated metamorphic rocks.

* Sketch a diagram illustrating how rocks of each of the three major classes can be altered by Earth processes to form new rocks.  On your diagram, be sure to distinguish between materials and processes.  Put boxes around the materials, and show the processes with arrows.

* Explain the rock cycle.

Department of Earth Science | Northeastern Illinois University

© 2007 Laura L. Sanders.  Last updated February 23, 2007.