Geology 102, Spring 2009

Mid-term #1 study reference

General statement. I take questions from my lecture notes to make up the exam. Much of my lecture material comes from the book, but not all. Reading the book thoroughly and reviewing my lecture notes should be sufficient preparation for the exam.

The following chapters will be covered on Mid-term #1

Appendix pages A1-A7

1: Earth in Context

3: Patterns in Nature: Minerals

Interlude A: Rock groups

4: Up from the inferno: Magma and igneous rocks

5: A Surface Veneer : Sediments, soils and sedimentary rocks (excluding sections 5.5, 5.6, 5.7)

6: Metamorphism- a process of change

Comments about my exams

I expect you to have a thorough understanding of those subjects listed here. I try very hard to construct questions that are on the major topics covered in lecture; in most cases these subjects are also covered in the book.  Note: I double-check the review sheet after I construct the exam to be sure that I only have asked questions on the subjects that I have listed for study.

A note about my questions: I have been accused of asking “tricky” multiple-choice questions.  By “tricky” what is meant is that answers may all seem like reasonable answers to the question, particularly if you have not studied. To that I say, “Guilty as charged!”   I will give you questions that require you to think through each answer before deciding which one is right.  I will do my best to limit factoid questions as they do little to satisfy you (or me!) that we are getting a worthwhile education.  Facts slip from memory quickly, but understanding the processes that govern our world are harder to forget once you’ve learned them.  These will stay with you even when there are no more classes.

The exam questions will be based on the following topics, which I have talked about in class and mostly are covered in the book. I strongly urge you to review your notes and read the text carefully before the exam.  I will formulate the questions from this pool of topics. Questions will be multiple-choice, fill in the blank, sketch a diagram, and a one-paragraph essay (you choose from one of three topics).

Topics:

Early Earth and Moon-forming event (hit by Mars-sized asteroid which ejected mantle to form Moon- note this happened within about 30 Myr. of the spernova that led to formation of our Solar System via the Nebular Hypothesis).

Earth’s internal heat: what are the four sources?

Earth's layers: recall earth is density-stratified

What are the primary compositional layers in Earth’s interior and on its exterior?

What are the primary layers of Earth based on physical properties (solid vs. liquid)?

Chemistry-

Planetary model for the atom: protons, neutrons, and electrons

Periodic Table- What do rows equate to in the planetary model of an atom? What do the columns mean in terms of electrons in outermost shell (ring)?

Why do elements chemically bond with other elements, particularly is the elements are electrically neutral before bonding? (recall filling outermost electron shell creates stability.

Chemical bonding- covalent and ionic- which is strong? Which is weak?

What’s mineral cleavage?  What role does chemical bnding have in developing cleavage? What role do the Si-O bonds in silicate minerals have in determining cleavage?

How does carbon dioxide differ from silicon dioxide (in other words, why is one a gads and the other the fundamental building block for silicate minerals)?

What is crystal form?

Silica tetrahedra: note how silica tetrahedra join together to form different groups of silicate minerals (isolated tetrahedral, chains, double chains, sheets, frameworks).

What’s  Bowen’s Reactions series and how does the structure of the silica tetrahedra relate to a mineral’s position within the series?

Mineral stability- why is quartz so abundant at Earth’s surface, whereas olivine and clinopyroxene are not? (hint: study Bowen’s Reaction series, and consider where Earth’s surface would plot on this diagram)

Mineral stability- note that minerals form in equilibrium with their environment (environment = temperature, pressure and chemistry).

Igneous, sedimentary, and metamorphic rocks- why does each form?  Recall that all three types of rocks are named based on rock texure.  Know those texture classifications.

How are rocks decomposed by weathering?

What are the two main types of weathering (A: physical and chemical)?

Why doesn’t quartz have cleavage?

Igneous rocks.  How does magma form in the mantle (recall P, T, volatiles)?  Where, globally speaking, do each of these three controls on magma formation occur? (recall mid-ocean ridges, subduction zones and mantle plumes).

What is crystal settling and how does it affect the magma’s density?

What must hapen to a magma's density before the magma can reach Earth's surface? What will this mean for the composition of rocks formed at the mid-ocean ridges versus rocks formed by passing through continental crust?

What is magma ponding and in what type of lithosphere is it likely to occur? Why?

What are the four main constituent of a soil?  What does the soil profile look like for a humid environment? How about an arid environment?

Know the different layers of a soil (O, A,E,B,C) and what happens in each.

What are the physical factors that contribute to soil formation?

What are the four categories of sedimentary rock?

How does each form?

What chemical factor causes some organic material to decompose whereas other organic material turns into coal or oil?

Metamorphic rocks

Why does metamorphism occur?

What are the physical factors that contribute to metamorphism (note that these are lidted above in mineral stability)?

What happens during metamorphism to minerals that remain stable through the environmental change?

What happens during metamorphism to minerals that become unstable through the environmental change?

Note that the addition and loss of chemicals may promote the growth of minerals that are compositionally different from the protolith (pre-existing rock)

Knw the facies of metamorphism and what type of metamorphism occurs at: midocean ridges, subduction znoes, around shallow plutonis, in deep parts of the lithosphere.