Multiple Choice (2 points each; 50 points total) -- Circle the BEST answer.

1. What is the term geologists use for a natrualyy occurring aggregate of minerals?
   1. Element.
   2. Isotope.
   3. Rock.
   4. Crystal.
   5. Compound.
2. The basic building block of silicate minerals is
   1. chains of silicon and oxygen atoms.
   2. the silicon-oxygen tetrahedron.
   3. the silicon ion.
   4. quartz.
3. Known for their tendency to split apart into thin sheets, micas have a silicate crystal structure that is characterized by
   1. isolated silicate tetrahedron.
   2. chains of silicate tetrahedron.
   3. sheets of silicate tetrahedron.
4. Which of the following techniques or instruments can be used to determine the distances between atoms in a crystal?
   1. Extinction of polarized light.
   2. Electron probe.
   3. X-ray diffraction.
   4. Reflecting goniometer.
5. When a substance is made of atoms which are arranged in an orderly and repeating pattern, it is said to be
   1. amorphous.
   2. glassy.
   3. crystalline.
6. The mantle of the Earth is probably composed of
   1. an iron-nickel alloy.
   2. silicates rich in iron and magnesium.
   3. quartz and felspars.
   4. metamorphic rocks like gneiss and mica schist.
7. The continental crust consists mostly of
   1. olivine.
   2. basalt.
   3. Fe + Ni.
   4. granite.
8. Quartz, SiO₂, has which of these structures?
   1. Isolated tetrahedron.
   2. Sheet.
   3. Double chain.
   4. Three-dimensional framework.
9. Which of the following is a native element?
   1. Quartz.
   2. Gold.
   3. Mica.
   4. Oxygen.
   5. Olivine.
10. Amphibole and pyroxene are
    1. chain silicates.
    2. sheet silicates.
    3. framework silicates.
    4. non-silicates.
11. Granite consists mainly of
    1. quartz, orthoclase (K-feldspar), Ca-plagioclase, and olivine.
    2. quartz, pyroxene, and muscovite.
    3. quartz, Ca-plagiclase, Na-plagioclase, and amphibole.
    4. quartz, orthoclase (K-feldspar), Na-plagioclase, and biotite.
    5. plagioclase, biotite, and muscovite.
12. Which of the following is NOT true of minerals?
    1. They are crystalline.
    2. They are organic.
    3. They are naturally occurring.
    4. They have a definite chemical composition.
    5. They possess characteristic physical properties.
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 minerals is a typical constituent of basalt?
    1. Quartz.
    2. Muscovite.
    3. Pyroxene.
    4. Na-plagioclase.
15. Obsidian (volcanic glass) is unusual because
    1. of its rare metamorphic origin.
    2. it contains no silica.
    3. it contains no minerals.
    4. it is an evaporite.
    5. it is very coarse-grained.
16. 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.
17. Which of the following are the first minerals to form (i.e., at the highest temperatures) in Bowen's reaction series?
    1. Quartz and feldspar.
    2. Halite and gypsum.
    3. Olivine and plagioclase.
    4. Mica and chert.
    5. Amphibole and plagioclase.
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. The most common gas released during eruptions is
    1. water.
    2. hydrogen.
    3. carbon dioxide.
    4. nitrogen.
    5. sulfur.
20. Which characteristic best distinguishes intrusive from extrusive igneous rocks?
    1. Composition.
    2. Grain size.
    3. Specific gravity.
    4. Color.
    5. Porphyritic versus non-porphyritic texture.
21. Explosive volcanic eruptions are usually associated with
    1. basaltic lavas.
    2. magmas which are low in both silica and dissolved gases.
    3. magmas which are rich in silica and dissolved gases.
    4. shield volcanoes.
22. A good example of a shield volcano is found in the
    1. volcanoes of the Washington and Oregon area.
    2. Hawaiian volcanoes.
    3. volcano in which Crater Lake is formed.
    4. volcanoes of the west coast of South America.
23. 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.
24. If someone informed you that an explosive eruption had taken place at an undisclosed location and that a huge nuee ardente flowed off the steep-sided volcano, you would inform the person that the magma type is likely to be
    1. basaltic.
    2. rhyolitic.
    3. ultramafic.
    4. gabbroic.
25. 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.