2. What layers (or parts of layers) form the “plates” (lithosphere) in plate tectonics? About how thick is the lithosphere? (3 points)

3. There are three different (general) types of plate boundaries. What are they? For each, give an example, and describe how each fits into the fundamental basis of plate tectonics (6 points).

a. _____________________ example: _____________________________

role in plate tectonics: __________________________________________________

b. _____________________ example: _______________________________________

role in plate tectonics: _________________________________________________________

c. _____________________ example: ________________________________________

role in plate tectonics: ________________________________________________________

4. What is a mineral? (2 points)

5. Name three minerals, including at least two silicate minerals, and give the essential elements comprising these minerals (if you know the formala, please give it) (3 points)

Name: _______________________ elements: ___________________________

Name: _______________________ elements: ___________________________

Name: _______________________ elements: ___________________________

6. What is the essential “building block” of all silicate minerals? What is its net electric charge? A particularly important mineral in the mantle of our planet has the formula (Fe,Mg)2SiO4. What is its name? How are the silicate building blocks arranged in this particular mineral, to be consistent with its formula? (4 points)

7. In the crust of Earth, what is the most important (by volume) group of silicate minerals? Why? (2 points)

8. Briefly define the three types of rocks: (6 points)

Name: ______________________ definition: ____________________________________

Name: ______________________ definition: ____________________________________

Name: ______________________ definition: _____________________________________

9. How do igneous rocks “fit” into the rock cycle? For example, what process might allow one type of rock to be changed into an igneous rock? How could igneous rocks be changed into other rocks? (3 points)

10. The terms mafic and felsic have been used to describe the two general compositional characters of igneous rocks (both intrusive and extrusive). Define each term, give names for rocks represented by these compositions, and compare and contrast the physical properties of these magmas. (8 points)

Mafic Felsic

a. Definition/important mineralogy:

b. intrusive rock name

c. extrusive rock name

d. viscosity

e. temperature

f. color

g. silica (not quartz) content

h. type of volcano

11. Below is a temperature/pressure graph (with temperature increasing from left to right as the x axis and pressure or depth increasing downwards, as the y axis). Draw a geothermal gradient and show the conditions for melting for a particular dry and wet geologic material; label all parts of the diagram accordingly (4 points).

12. What is the concept of uniformitarianism? How did the advocates of this idea view the age of Earth?

II. Multiple Choice Questions (two points each)

1. In the nebular hypothesis for the origin of our solar system,
a. the large cloud composed of small rocky fragments and gases, most notably hydrogen and helium, contracted under the influence of gravity, beginning some 5 billion years ago
b. the inner, solid, heavy planets originated by accumulation of both metallic and rocky debris
c. appreciable amounts of lighter elements were unable to be retained by the inner planets
d. the large outer planets (Jupiter, Saturn, Uranus, Neptune) accumulated most of the light elements from the original cloud of primordial material
e. none of the above
f. all of the above

2. Which of the following volcanic chains is representative of a plate tectonic setting where oceanic lithosphere is subducted beneath oceanic lithosphere,
a. Cascade Range
b. Andes Mountains
c. Hawaiian Islands
d. Aleutians

3. At a mid-ocean ridge (spreading center) environment, what type of lava is most likely to erupt?
a. andesite
b. basalt
c. ultramafic composition
d. rhyolite
e. none of the above

4. In what kind of plate tectonic setting did Mt. St. Helens form?
a. mid-ocean ridge
b. subduction zone, with oceanic lithosphere descending beneath the margin of continental lithosphere
c. subduction zone, with continental lithosphere descending beneath the margin of oceanic lithosphere
d. subduction zone, with oceanic lithosphere descending beneath the margin of oceanic lithosphere
e. none of the above.

5. In the crystallization of an igneous rocks, what mineral is the first to form (at the highest temperatures) in the discontinuous branch of Bowen’s reaction series?
a. amphibole
b. quartz
c. potassium feldspar
d. olivine
e. biotite

6. What mineral forms at lowest temperatures in the continous branch of the series?
a. biotite
b. sodium feldspar
c. olivine
d. quartz

7. Of the following minerals, which is typically one of the last to form in a solidifying igneous melt?
a. olivine
b. amphibole
c. calcium feldspar
d. quartz

8. All silicate minerals
a. are hydrous, in that they have molecular water tied in their crystal structure
b. display excellent cleavage, in that they have one or more preferred planes of weakness reflecting weak chemical bonds in their crystal structure
c. are anhydrous, in that they do not contain molecular water in their crystal structure
d. contain iron (Fe) and magnesium (Mg) as important elements
e. none of the above
f. all of the above

9. The geothermal gradient
(a) never intersects the melting curve of geologic materials
(b) is simply the increase in temperature with depth in the Earth, and changes slope with depth in the mantle
(c) is simply the increase in temperature with depth in the Earth, and remains constant to the base of the mantle
(d) has an average value of 500oC per kilometer in the interior of the Earth
(e) intersects the melting curve of geologic materials at an average depth of 20 kilometers below Kansas

10. In the silicate tetrahedron, the silicon atom (with tendency to become a cation) has a coordination number of (or is surrounded by how many oxygen atoms.
(a) 2, (b) 3, (c) 4, (d) 6, (e) 12.

11. Which of the following statements about a scientific theory is not true?
(a) it is the best available explanation for a particular natural phenomenon based on empirical (observational) evidence
(b) it is based on a large body of supporting evidence, gathered by numerous scientists
(c) it is a conjecture or guess
(d) it is testable
(e) it assumes no pre-conceived notion or “faith” in one explanation over another for a particular natural phenomenon
(e) none of the above

12. The velocity of lithosphere plate motion (i.e. the rate of formation of oceanic lithosphere at mid-ocean ridges) is
(a) typically is on the order of kilometers per year
(b) cannot be measured
( c) is comparable to the rate at which your fingernails grow
(d) typically on the order of centimeters per million years.

13. What fundamental process is believed to be responsible for plate motion?
(a) subduction
(b) hot spot activity
(c) spreading ridges
(d) convection cells in the mantle
(e) density differences

14. To which of the following groups do most minerals in the earth's crust belong?
(a) carbonates
(b) oxides
(c) silicates
(d) halides
(e) native elements

15. To emphasize the concept of plate tectonics, I showed a simple experiment where a layer of relatively cold, solid material, of relatively high density, is carefully placed above a material in a liquid or partially liquid state. The liquid or partially liquid state corresponds to
a. the asthenosphere, which lies beneath the lithosphere
b. the asthenosphere, which is composed primarily of silicic composition (as opposed to mafic or ultramafic composition) rocks
c. the lithosphere, which behaves plastically and deforms or flows slowly
d. the crust
e. all of the above

II. Cross Section Sketch (8 points)

On the next page, sketch a two-dimensional vertical cross section of part of the earth’s crust showing geometric relations among different intrusive and extrusive igneous rock bodies. Include, for example, dikes, batholiths, volcanoes, volcanic necks, etc. Do not hesitate to provide as much detail as you can, including an approximate scale for the diagram.