GLY 220: Physical Geology Exam 1 Review Sheet What to expect Exams for GLY 220 are composed of 50 multiple-choice questions. The only thing you need to bring to the exam is a Number 2 pencil with an eraser. You do NOT need to buy scantrons; I provide these for you free of charge. No calculators are required or permitted. The exam will not be administered until everyone has left personal items (backpacks, purses, cell phones, etc.) at the front of the class, cleared their desk, and stopped talking. You may keep cell phones in your pocket, but if they are seen at any time during the exam, you will automatically receive a zero. When you are finished, please turn in both your exam and answer sheet to me at the front of the class. Material covered on the exam Exam 1 will cover ALL MATERIAL discussed in lecture from the first day of class to the end of the lecture on metamorphic rocks. “All material covered in lecture” includes everything we discussed in class, including any videos, whether or not it appears on the PowerPoints. For example, some slides in my PowerPoints are photographs or maps without much accompanying text; what I said in class while those slides were on the screen is fair game on the exam. I hope you took good notes of that material! In the bulleted listing below, I list what a summary of the topic you should focus on for Exam 1. Some students misunderstand the purpose of this list, so I have added these important disclaimers: 1. THE BULLETED ITEMS ARE NOT QUESTIONS YOU WILL SEE WORD FOR WORD ON THE EXAM; they are merely a TOPICAL SUMMARY of the material that I think is most likely to appear on the exam. Most questions will test your knowledge, and to a lesser extent application, of this material. Other questions will test your application of skills learned during this course (i.e., how to recognize various geologic features from photographs, etc.). 2. The questions on the exam are MORE DETAILED than the topics listed below. Remember, EVERYTHING discussed in class is fair game, including DETAILS. To help you appreciate this, I have included 15 sample questions from last year’s exam at the end of this review sheet (you can find the answers to these questions yourself). These questions will probably not occur on this year’s exam, but who knows, I may just get lazy and use them again. 3. Not everything on the exam will necessarily come from this review sheet, and not everything on this review sheet will be on the exam.
Introduction • What is geology? physical geology? • How is geology related to other sciences? Science and the scientific method • What is science? What isn't science? • What are the limits and assumptions of science? • What is uniformitarianism? What is it not? • What are some components of and problems with the simplified "scientific method"? Minerals • What is a mineral? • How does a mineral’s crystal structure affect its (a) external morphology, and (b) physical properties? • What are polymorphs?
2 What are the processes by which minerals are formed in nature? What is the basic building block of the silicate minerals? What are the basic types of silicate crystal structures? What are the 8 most important rock-forming silicates? How and why are mafic silicates different from felsic silicates? • What minerals are responsible for expanding soils? Where are they found? • What are the 5 most important rock-forming non-silicates? • You will not be responsible for knowing any mineral formulas • • • •
Rocks: an introduction • What is a rock? • What are the three main types of rocks, and the processes involved in their formation? • What are the components (materials and processes) of the rock cycle? Magmas and intrusive igneous rocks • What are the various components of magma? (i.e., magma can contain more than just melt) • How are intrusive and extrusive igneous rocks different in terms of their texture (grain size)? • What variables control which minerals crystallize from magmas? • Be able to use Bowen's reaction series (it will not be provided for you) to qualitatively determine the temperatures and/or compositions of igneous magmas/rocks. You won't have to reproduce it, but you may see questions like this: "An igneous rock is dominated by the minerals olivine and pyroxene. Did this rock crystallize from a high-temperature or a low-temperature magma?", or "True or false: Felsic magmas are generally hotter than mafic magmas". • Mineral compositions of common igneous rock types: here are some sample questions: “What is the name of a fine-grained rock dominated by olivine and pyroxene? or “Name two minerals that commonly crystallize from mafic magmas”. • What are the main processes contributing to the diversity of magma types? Know how each process works. • Be able to identify the five types of igneous intrusions from photos or diagrams (these photos may or may not be the ones I showed in class) Volcanoes and extrusive igneous rocks • What are the effects of silica and water content on the eruptive behavior of magmas? • What are some characteristics of basaltic and rhyolitic lava flows? • What is the difference between pahoehoe and aa lava? Be able to identify each from images of lava flows. • What is the origin of pyroclastic volcanic deposits? How are they classified? What is tephra? tuff? • Be able to identify from pictures/diagrams the five types of volcanoes (shield, cinder cone, stratovolcano, dome, and caldera) • Be able to match names of famous volcanoes with the various volcano types • See the notes sheets for the video we showed in class; everything on it is fair game Sediments and sedimentary rocks • Be able to define or discuss aspects of the 6 processes that form sedimentary rocks • How are rounding, sorting, and mineral content in sedimentary rocks related to the duration and distance of weathering/transport? For example, which has seen more weathering/transport: a poorly-rounded sandstone or a well-rounded sandstone? a sedimentary rock with a fair amount of feldspar and biotite in it, or a sandstone primarily composed of quartz? • What are the three main categories of sedimentary rocks and how are they formed? • How does the grainsize of a clastic rock generally relate to outcrop expression (cliff vs. slope)? • Be able to interpret something about the sedimentary environment from each type of structure (for example, mudcracks → wet sediment, usually mud, has been exposed at the surface and dried out) • Be able to identify sedimentary structures from photographs (you should also be able to determine current direction from cross-bedding) • Be able to match various sedimentary environments to a list of sediment types, rock types, sedimentary structures, and other characteristics of those environments
3 Metamorphism and metamorphic rocks • What is meant by the term "protolith"? • What effects (in terms of textural and mineralogical changes) result from subjecting a rock to increased temperature? pressure? • What is a geotherm? • What is foliation, and what does it tell you about pressure conditions during metamorphism? What are some consequences of foliation for roads and dams? • Be able to describe the textural and compositional features associated with the various types of metamorphic rocks we mentioned in class • Texturally and mineralogically, what happens to shale protoliths during progressive stages of metamorphism? • What are some common minerals found exclusively in metamorphic rocks? • How does a geologist compile a map of metamorphic grade in a metamorphosed region? • Describe the pattern of metamorphic grade as observed in rocks in New England. Where is the lowest grade metamorphism in this region? the highest grade metamorphism?
15 SAMPLE QUESTIONS Here are 15 sample questions from last year’s exam. Notice how most of these questions correlate with material on the list of topics above, but are MORE DETAILED. These questions will probably not occur on this year’s exam, but I am not ruling anything out, either. 1.
During the 17th and 18th centuries, science a. was separated from other sources of knowledge b. was known as “natural philosophy” c. developed rapidly during an age of discovery, industrial revolution, and political revolution d. all of the above e. none of the above
2.
Natural science is totally independent of philosophical assumptions. a. true b. false
3.
According to the definition given in class, a mineral would NOT include which of the following? a. ice within a glacier on the continent of Antarctica b. grains of quartz on a beach in Rio de Janiero, Brazil c. synthetic rubies made in the laboratory d. a and b
4.
Quartz is a. a sedimentary rock b. an igneous rock c. a metamorphic rock d. none of the above
5.
On the rock cycle diagram that we presented in class, what process(es) directly follow(s) the production of sedimentary rocks? a. uplift b. increased heat and pressure c. weathering and erosion d. a and b e. b and c
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6.
What minerals are commonly present in mafic igneous rocks like gabbro? (hint: think of Bowen’s reaction series) a. quartz, feldspar, and biotite b. garnet, staurolite, and kyanite c. plagioclase and pyroxene d. mostly just olivine
7.
Would it be possible to find a pluton made out of rhyolite? a. yes b. no
8.
Which type of sediment settles from water flowing at the highest velocity? a. sand b. mud c. silt d. gravel
9.
Precipitation of gypsum due to evaporation of seawater produces which kind of sedimentary rock? a. biochemical b. chemical c. clastic d. felsic
10. Which variable controls how explosive a volcanic eruption is? a. iron content b. volatile content c. depth of magma generation d. magma temperature 11. Which sedimentary rock type is composed of material that has traveled the farthest distance? a. conglomerate b. sandstone c. shale d. basalt 12. Sediments deposited from a glacier are characterized by a. poor sorting and poor rounding b. graded bedding and bioturbation (burrows) c. well-rounded grains and cross-bedding d. all of the above 13. Geotherms a. are graphs showing how pressure changes with increasing depth within the Earth b. are graphs showing how temperature changes with increasing depth within the Earth c. are always the same from place to place d. none of the above 14. Which metamorphic rock is the lowest-grade? a. schist b. phyllite c. gneiss d. slate
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15. The protolith of marble is a. sandstone b. schist c. shale d. limestone
SOME TERMS TO KNOW Since the exam is multiple choice, you will NOT need to write a full definition for any of these terms. However, you should know what these things are to the degree that we talked about them in class. For example, for “andesite”, all you need to know is that it is a volcanic rock with intermediate silica content; for “kyanite”, all you need to know is that it is a mineral found exclusively in metamorphic rocks. Many of these terms can also be found in the glossary in the back of your textbook. geology physical geology science uniformitarianism hypothesis theory mineral crystal polymorphs crystallization precipitation vein solid-state diffusion polymerization montmorillonite bentonite quartz plagioclase feldspar potassium feldspar muscovite mica olivine pyroxene amphibole biotite mica felsic mafic calcite gypsum halite hematite magnetite rock igneous sedimentary metamorphic magma intrusive / plutonic
extrusive / volcanic peridotite basalt gabbro andesite diorite rhyolite granite partial melting magma mixing fractional crystallization dike sill laccolith pluton batholith volatile pahoehoe aa tephra tuff shield cinder cone stratovolcano / composite cone dome caldera crater lake ash fall ash flow / pyroclastic flow weathering erosion diagenesis cement mudstone / shale siltstone sandstone conglomerate
rock salt rock gypsum travertine limestone chert coal bedding cross-bedding graded bedding ripple marks mud cracks fluvial alluvial fans evaporite protolith geotherm recystallization foliation lineation folds garnet kyanite staurolite corundum slate phyllite schist gneiss hornfels quartzite marble prograde retrograde migmatite isograd