Multiple Choice -- Circle the BEST answer.

1. The chemical bond within an ionic compound is formed by
   1. electron sharing.
   2. neutron sharing.
   3. gain or loss of electrons.
   4. gain or loss of protons.

2. What is the smallest unit of an element that retains the chemical and physical properties of that element?
   1. Atom.
   2. Nucleus.
   3. Electron.
   4. Proton.
   5. Neutron.

3. Quartz is
   1. a compound.
   2. a mineral.
   3. composed of two elements.
   4. all of these.

4. The two most abundant elements of the Earth's crust are
   1. oxygen and iron.
   2. iron and silicon.
   3. magnesium and iron.
   4. silicon and oxygen.

5. The principle of superposition states that in unfolded, sedimentary layers
   1. layers at the top of the pile are always older than those beneath them.
   2. layers at the top of the pile are always younger than those beneath them.
   3. sediments generally accumulate in the vertical sequence sandstone-shale-limestone.
   4. overlying strata extend over a broader area than the layers beneath them.

6. The structure of pyroxene, (Mg, Fe)SiO₃, consists of
   1. isolated silica tetrahedra.
   2. linked pairs of silica tetrahedra.
   3. single chains of silica tetrahedra.
   4. double chains of silica tetrahedra.

7. Which of the following is not classed as a mineral?
   1. Native copper.
   2. Diamond.
   3. Glass.
   4. Water ice.

8. A single chain of silicon-oxygen tetrahedra is well illustrated by the crystal lattice structure of the
   1. olivine group.
   2. pyroxene group.
   3. amphibole group.
   4. plagioclase group.

9. The continental crust consists mostly of
   1. olivine.
   2. basalt.
   3. Fe + Ni.
   4. granite.

10. Which of the following is a native element?
    1. Quartz.
    2. Gold.
    3. Mica.
    4. Oxygen.
    5. Olivine.

11. Amphibole and pyroxene are
    1. chain silicates.
    2. sheet silicates.
    3. framework silicates.
    4. non-silicates.

12. Granite consists mainly of
    1. quartz, orthoclase (K-feldspar), Ca-plagioclase, and olivine.
    2. quartz, pyroxene, and muscovite.
    3. quartz, Ca-plagioclase, Na-plagioclase, and amphibole.
    4. quartz, orthoclase (K-feldspar), Na-plagioclase, and biotite.
    5. plagioclase, biotite, and muscovite.

13. A rock with the same mineralogy as granite but with fine grain size is
    1. basalt.
    2. obsidian.
    3. gabbro.
    4. rhyolite.
    5. pumice.

14. Which of the following will contain the most silica?
    1. Andesite.
    2. Basalt.
    3. Fissure eruptions.
    4. Rhyolite.

15. As a magma crystallizes and differentiates, following the Bowen reaction series, the lower temperature fractions of liquid magma are progressively
    1. enriched in magnesium.
    2. depleted in potassium.
    3. depleted in silica.
    4. enriched in silica.

16. The first mineral to crystallize in the discontinuous branch of Bowen's reaction series is
    1. olivine.
    2. plagioclase.
    3. quartz.
    4. biotite.
    5. pyroxene.

17. The discontinuous reaction series observed in the crystallization of mafic minerals is "discontinuous" because
    1. heavy mafic crystals sink to the bottom of the magma chamber.
    2. ions with different charges replace one another in the crystal structures.
    3. minerals with different crystal structures and compositions replace one another.
    4. these minerals crystallize out at very high temperatures.

18. Most of the rock exposed on a shield volcano is
    1. pyroclastic in origin.
    2. ash and bombs.
    3. felsic in composition.
    4. basalt.
    5. gabbro.

19. Which of the following is the major constituent of volcanic gases?
    1. Water vapor.
    2. Nitrogen.
    3. Carbon dioxide.
    4. Sulfur dioxide.

20. Basalt can be produced by the partial melting of
    1. rhyolite.
    2. ultramafic rocks.
    3. gabbro.
    4. a mixture of gabbro and oceanic sediments.

21. Igneous rocks are named using two important characteristics. These are
    1. intrusive and extrusive.
    2. fine-grained and coarse-grained.
    3. texture and composition.
    4. phenocrysts and groundmass.

22. Based on Bowen's reaction diagram, a zoned plagioclase crystal should
    1. be richer in iron than in magnesium.
    2. have a center richer in calcium and concentric layers progressively richer in sodium.
    3. have a center richer in sodium and concentric layers progressively richer in calcium.
    4. have a sheet-like crystal structure.

23. Which pair of rocks are associated with high silica content?
    1. Basalt and gabbro.
    2. Granite and andesite.
    3. Ultramafic rocks and rhyolite.
    4. Rhyolite and granite.
    5. Diorite and andesite.

24. Pegmatites are extremely coarse-grained because
    1. they cool even slower than a large pluton.
    2. of the high water pressure.
    3. they are made of mantle rock.
    4. they move rapidly toward the surface.

25. Andesites are predominantly the product of
    1. partial melting of ocean crust and sediments.
    2. partial melting of ultramafic rocks from the mantle.
    3. partial melting of granite and granodiorite.
    4. fractional crystallization of granite.

26. Which of the following states is essentially all volcanic rock?
    1. California.
    2. Oregon.
    3. Washington.
    4. Hawaii.
    5. Alaska.

27. Your friends describe a recent hike up the gentle slope of a large mountain. On their three-day hike, they frequently crossed lava flows, fissures and occasionally took a detour around a cinder cone. You inform your friends that they were hiking on a
    1. caldera.
    2. composite volcano.
    3. gabbro pluton.
    4. shield volcano.

28. Large volumes of andesite lava are extruded
    1. along zones of lithosphere plate separation (oceanic ridges).
    2. along continental rift valleys.
    3. where two lithospheric plates converge.
    4. by individual volcanoes within the oceanic plates.

29. Explosive volcanic eruptions are usually associated with
    1. basaltic lavas.
    2. magmas which are low in both silica and dissolved gases.
    3. magmas rich in silica and dissolved gases.
    4. shield volcanoes.

30. If lava flows on the flanks of a composite volcano erupted from one large magma chamber which slowly crystallizes, predict how their gross composition would change over time?
    1. Younger lava flows would become progressively enriched in silica and become more felsic.
    2. Younger lava flows would become progressively enriched in iron and become more mafic.
    3. Lava flows would alternate in composition.
    4. Lava flows would be the same composition since they all came from the same magma chamber.

31. Calderas are usually associated with
    1. basaltic lava forming as flows.
    2. abundant ash and related pyroclastic debris.
    3. relatively quiet eruptions.
    4. shield volcanoes.

32. What are the two most fundamental levels to the Earth's surface?
    1. Land and oceans.
    2. Mountains and trenches.
    3. Crust and mantle.
    4. Continental crust and ocean basins.

33. Fine-grained feldspar weathers more rapidly than coarse-grained feldspar because
    1. relatively more surface area is available to be attacked by solution.
    2. smaller grains are mechanically less stable, so they tend to fracture more easily.
    3. chemical bonds are weaker in the smaller grains than large ones.
    4. smaller grains pack less closely together, allowing water to percolate through the rock more easily.

34. Where is chemical weathering most effective?
    1. Warm, dry climates.
    2. Warm, wet climates.
    3. Cool, dry climates.
    4. Cool, wet climates.
    5. At the shoreline.

35. The major source of salts dissolved in ocean water comes from
    1. marine organisms.
    2. weathering of the land surface and volcanic volatiles.
    3. weathering of the ocean crust.
    4. meteorites.
    5. none of the above.

36. Acid rain ____________ the potential for chemical weathering.
    1. decreases.
    2. has no effect on.
    3. increases.
    4. neutralizes.

37. The following are all products of chemical weathering except
    1. feldspar.
    2. silica in solution.
    3. iron oxides.
    4. clay minerals.
    5. soluble salts.

38. Clay minerals have a silicate structure similar to that of
    1. feldspar.
    2. amphibole.
    3. mica.
    4. quartz.
    5. pyroxene.

39. Although water is an important agent of chemical weathering in its own right, it becomes more effective if small amounts of carbonic acid are present. Carbonic acid is formed when
    1. carbon from coal beds or from graphite deposits is pulverized along a fault or fracture and then added to the water.
    2. carbon dioxide from the atmosphere or from organic decomposition is added to water.
    3. sulfur from coal-fired power plants is added to water.
    4. water comes in contact with the calcite in a limestone layer.

40. Which of these rocks is most susceptible to solution?
    1. Limestone.
    2. Shale.
    3. Basalt.
    4. Gneiss.

41. The most important factor in soil development is
    1. topography.
    2. climate.
    3. parent rock.
    4. time.

Short Answers -- Briefly discuss the relationship between the following paired terms.

1. Granite / Rhyolite

2. Porphyritic igneous rock / Cooling rate

3. Volcanism / Ocean crust

4. Acid rain / Chemical weathering

5. Feldspars / Clay minerals

6. Obsidian / Cooling

7. Andesite / Diorite

8. Physical weathering / Chemical weathering

Fill-in-the-Blanks

1. The diagram below illustrates a geologic outcrop with three layers of sedimentary rocks, one fault and one igneous rock body called a dike. List the relative sequence of geologic events from youngest to oldest.
   

   Youngest		__________________________________________________
   		__________________________________________________
   		__________________________________________________
   		__________________________________________________
   Oldest		__________________________________________________

2. In the diagram below name the two crustal plate boundaries marked.
   

   A.__________________________________________

   B.

   __________________________________________

Circle the Best Answer

A large magma body sits below a composite volcano which erupts intermittently.

Some of the early formed crystals will be enriched / depleted in iron and magnesium.

As crystallization proceeds, the remaining magma becomes progressively enriched / depleted in silica.

If the initial magma was mafic in composition, then the first mineral likely to form is olivine / mica / quartz.

If crystal settling occurs, the more recent lava flows will be more mafic / felsic.

If an eruption occurs after partial crystallization of the magma, the lava flow is likely to be aphanitic / phaneritic / porphyritic in texture.

Matching

Match the numbered column of terms with the lettered column of terms.

_______		1. feldspar			A. Mineral having one direction of perfect cleavage
_______		2. mica			B. Hardest mineral
_______		3. Fe, Mg silicate			C. Most common mineral
_______		4. diamond			D. Highest density minerals
_______		5. oxygen			E. Most common element

Discussion Questions -- Answer the following discussion questions. Be as complete as possible. Illustrate your answers with diagrams or sketches.

1. What is meant by the statement that there is a positive feedback between physical and chemical weathering?
2. Discuss the relationship between chemical weathering and acid rain. Be sure your statement includes the following:
   1. Source(s) of acid rain.
   2. Role of acids in chemical weathering.
   3. Description of one important chemical reaction involving acids and silicate minerals, like feldspars.

3. There are five main structural types of silicate minerals; examples of the five are olivine, pyroxene, amphibole, mica, feldspar. Describe the five structures, including what they have in common and how they differ from each other. For full credit, simple diagrams of at least three of the structures must be given.

4. A geochemist and petrologist have just finished studying a volcanic field. Here is what they found. The field consists of a high, rather irregular central peak, surrounded by a large, flat expanse, dimpled with cinder cones, and associated lava flows. The peak is made out of a series of flows and pyroclastic debris of varying thickness and composition. The younger flows were enriched in sodium, potassium, and silica, compared to the older flows. In contrast, the cinder cones and associated lava flows were all basaltic with only minor variation in composition. Based on these findings, the geologists concluded that the lavas, which construct the peak, were derived from a single, probably relatively large, magma chamber. Whereas, the cinder cones and associated basaltic flows came from small, separate magma bodies. Do you agree with their conclusions? Explain.

5. Compare and contrast a shield volcano, composite volcano and caldera. Include in your comparison how these three types of volcanoes differ in
   • features, e.g., flows, domes, cones, pyroclastics;
   • shape/topography, include a sketch of each;
   • style(s) of eruption;
   • magma type(s) and physical properties of magma; and
   • geologic hazards/potential impact on planet.
   Consider organizing your answer in a table format.
6. Friends of yours just returned from a trip during which they witnessed a volcanic eruption. They spent hours watching lava erupt from a fissure. The thin sheet of lava flowed for miles.
   1. What kind of magma erupted, e.g. basaltic, andesitic, or rhyolitic? Explain your choice.
   2. Discuss two important factors that influence the style of eruption; e.g. lava flow vs. explosion.
7. Andesites and basaltic andesites are common rocks in volcanic arcs, associated with convergent plate margins (refer to diagram). Using your knowledge of Bowen's Reaction Series and igneous rocks, discuss why magmas generated in subduction zones are somewhat different in composition from the basaltic ocean crust from which the magmas are thought to be derived.
8. Recent studies of the volcanic eruptions in Iceland have revealed a very curious link between glaciation and volcanic activity. The number and volume of basaltic eruptions seems to have significantly increased after the last ice age about 10,000 years ago. Given your knowledge on what causes rocks to melt, discuss a possible reason for this apparent link between volcanic activity and removal of the thick ice cap that once covered Iceland.
9. Based on your knowledge of Bowen's Reaction Series and the distribution of igneous rocks in the Earth's crust and mantle, describe three processes by which the composition of rocks generated from a single large magma chamber can change over the time it takes for the magma chamber to solidify.
10. Why are the physical properties of graphite and diamond so different, even though they are both made from 100% carbon?

Last updated: 2/15/98
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