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					                      Homework Questions for Lecture 10
                             ES 1000


Use these questions to test your knowledge of Lecture 10.

A. Short answer:

   1. An _________ suite is the sequence of rocks that makes up oceanic
      lithosphere.

   2. An __________ is the inactive arm of a three-branched fracture
      (Triple Junction) that forms after the initial stages of continental
      rifting.

   3. Plumes form in the deepest parts of the mantle, near the liquid outer
      _______.
   4. Hot spots move much more slowly than the overlying _______.

   5. The speed of tectonic plate movement varies from plate to plate in the
      range of 1 to 10 ___________ per year.

   6. The breakup of Pangaea occurred about _______ million years ago.

   7. In the future, western _________ will probably become detached from
      the rest of North America along the San Andreas Fault, forming a new
      microcontinent.

   8. A suture zone is the boundary between continents that have
      ___________

   9. __________ Terranes are fault-bounded rock bodies that originated in
      one place and have been transported to a continental margin.
B. Match the Terms.

1. Suture zone_____             a. accretionary wedge

2. Divergent zone quakes ____    b. sediments, basalt, gabbro, peridotite

3. Mantle convection____        c. failed arm of a Triple Junction

4. Craton____                   d. chimney structures mid-ocean ridge

5. Mélange ____                 e. seamount

6. Volcano caused by plume ___ f. two continents collided

7. Black smokers_____           g. shield and platform

8. Aulocogen ______             h. drives plate motion

9. Guyots ______                 i. between offset ridge segments

10. Ophiolite _____             j. flat-topped
C. True or False? Circle the correct answer.

   1. The chimney-like structures around the mid-ocean “black smokers”
   are encrusted with mineral precipitates rich in salts. True or False?

   2. The speed of tectonic plate movement varies from plate to plate in the
   range of 1 to 10 meters per year. True or False?

   3. We can measure plate velocity with radiometric dating of seamount
   chains, or the distance of a marine magnetic anomaly from a mid-ocean
   ridge. True or False?

   4. Marine magnetic anomalies (magnetic "stripes") are often symmetrical
   about mid-ocean ridges. True or False?

   5. The Hawaiian Islands and the Emperor Seamount chain were formed
   because the Pacific plate is moving over a nearly stationary hot spot.
   True or False?

   6. Guyots are flat primarily because they have been planed off by
      weathering, erosion, and ocean waves. True or False?

    7. The youngest seamount will be the closest to the hot spot, and an
   arrow from the youngest seamount to the next closest seamount indicates
   the direction of plate movement. True or False?

   8. Hot spots can be used as “fixed” reference points for determining plate
   speed and direction because they move much more slowly than the
   overlying plates. True or False?

   9. The Red Sea contains active convergent margins. True or False?

   10. The Great Rift valley of East Africa may be a failed arm (aulocogen)
of a three-branched rift (Triple Junction). True or False?
D. Multiple choice:

1) Unconsolidated sediments atop ocean lithosphere contain all of the
   following EXCEPT:
   (a) siliceous microscopic marine organisms.
   (b) calcareous microscopic marine organisms.
   (c) pillowed basaltic lavas.

2) The correct sequence of an ophiolite suite, from top to bottom, is:
   (a) unconsolidated sediments, basalt layer, gabbro, peridotite.
   (b) unconsolidated sediments, gabbro, peridotite, basalt layer.
   (c) unconsolidated sediments, basalt layer, peridotite, gabbro.
   (d) basalt layer, unconsolidated sediments, gabbro, peridotite.

3) At divergent zones, earthquakes commonly occur:
   (a) beyond the ridge segments, where segments move in the same
       direction.
   (b) between offset segments, where segments move in opposite
       directions, and also near the ridge axis.
   (c) on the abyssal plain, away from the ridge
   (d) about 750 km beneath the ridge

4) The correct sequence of subduction-zone features from land seaward is:
    (a) continent, forearc basin, accretionary wedge, volcanic arc, backarc
        basin, trench.
    (b) continent, accretionary wedge, backarc basin, trench, forearc basin,
        trench, volcanic arc.
    (c) continent, backarc basin, volcanic arc, forearc basin, accretionary
        wedge, trench.
    (d) continent, backarc basin, accretionary wedge, volcanic arc, forearc
        basin, trench.
5) Which of the following tectonic features has been incorporated into the
   Himalayan mountain belt?
   a) Accretionary wedges.
   b) Volcanic arcs
   c) Forearc and backarc basin rocks
   d) All of the above.

6) Which of the following statements concerning displaced terranes is
   TRUE?
   a) They are distinguished from surrounding rocks by their different ages,
      structures, mineralogies, fossil assemblages, and magnetic properties.
   b) They originated from somewhere other than their present locations.
   c) Many formed as volcanic island arcs or as pieces broken off from
      other continents.
   d) All of the above

7) Pangaea was formed by the collision of which two landmasses?
   a) North America and South America.
   b) Gondwana and Rodinia.
   c) Gondwana and Laurasia.
   d) Laurasia and Rodinia.

E. 1. Short answers

      Discuss the creation of the Emperor Seamount chain and the Hawaiian
      Islands. In particular:
            a. What is a Plume?
            b. Why is the big Island of Hawaii the largest of the Hawaiian
            Island Chain?
            c. Why do the islands regularly decrease in size west of
            Hawaii?
            d. Why do the islands turn northwest at the Emperor Chain?
            e. How could you estimate the rate of Pacific Plate Movement?
F. Calculations
Last time we continued our work on data that tested an old idea from
forestry: Red Maples will tolerate wetter soils than Red Oaks. Our null
hypothesis H0 was that “there is no difference in soil moisture near them”.

Answer a., b., and c. below.
In red numbers below are the ( O - E )2 / E values we got for the last
homework. O is the initial observation of soil moisture near trees.




To calculate a Chi-squared value, add up all of the red numbers.

x 2 = ∑ (O – E) 2
         (           )   a. Enter your result: X2 = ____________________
              E

To see if this number is reasonable for our null hypothesis H0, compare it to
the table of critical values below. Reject the null hypothesis if your Chi-
squared value is greater than the critical value for the 0.05 level. Degrees of
freedom (d.f.) is 4 i.e. (5 columns -1) x ( 2 rows – 1) of data.
b. H0 is (circle one: accepted/rejected) c. State the accepted hypothesis:

df P = 0.05 P = 0.01 P = 0.001
1 3.84       6.64    10.83
2 5.99       9.21    13.82
3 7.82       11.35   16.27
4 9.49       13.28   18.47

				
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