THE UNIVERSITY OF WESTERN ONTARIO

LONDON                                           CANADA

Final Examination       -      Summer Term 2003

Time: 3 hours                            Earth Sciences 240A                          Distance Studies

(No electronic materials permitted)

 

PART A

Answer ONE of the following three questions. Each question is valued at 20 marks.

Each question may be answered in as little as two pages of single spaced (essay format) writing (if you prefer double spaced answers, do the math!). Obviously, you may use as little space as you wish, but each topic must be fully discussed in whatever space you use. Please do not use point-form answers except where a listing is appropriate within an essay answer. Use illustrations to strengthen/support discussions, but not in substitution for words.

 

  1. Meteor Crater in Arizona was discovered a long time ago, but was not acknowledged to be the product of impact until relatively recently. Based upon (a) the knowledge you now have of that crater, the area around it, and the character of the meteoroid that produced it; and (b) your current excellent knowledge of impact objects and their effects, discuss how you would identify and fully define such a feature if you stumbled across an identical one today in, say, Canada’s Northwest Territories.
  2. You have been mapping a continuous sequence of horizontally stratified marine sedimentary rocks. From the bottom of the sequence up, there has been an abundance of hard-shelled fossils, but at one very well defined horizon they nearly all disappear! The rocks immediately above that horizon have almost no fossils, but progressively higher layers in the sequence gradually contain more and more fossils. Describe in detail what you would do to determine if this is evidence of a previously undiscovered mass extinction event.
  3. In Mid-Cretaceous times, only about 12% of the globe was dry land, thus seas were abundant. Seas were relatively warm and all life –especially marine life – was thriving. At the end of Cretaceous there was a terrific mass extinction of all life, terrestrial and marine. At just about this time, India was situated over a mantle plume (creating a dramatic hot spot) and the Deccan Traps were erupted. No matter what you (or I) might think about an impact cause for the mass extinction, a host of scientists still believe it was caused (totally) by the Deccan Trap eruptions. Your task is to critically review the hard evidence collected from the geologic record, and convince that host of scientists that they are wrong.

 

PART B

Fill in the missing word(s). Please put your answers, in sequential order, in the answer booklet – NOT on this examination sheet. Each question is valued at 1 mark.

  1. Carbon isotope age dating is useful only for C-containing items less than ___________ (number) years of age.
  2. Products of early supernovae are part of your personal composition. ________(True/False)
  3. ___________ is known as the ‘Father of Catastrophism’.
  4. Earth should expect one Zhamanshin-size asteroid to impact every _________ years.
  5. In determining the kinetic energy of a meteoroid, the most important factor is __________________.
  6. The average life span of any species is about ___________ (number) million years.
  7. The southern block of Pangaea was called __________________.
  8. When there is a slow but continuous movement of both sides (relatively) of a fault, the motion is called _______________.
  9. A compression seismic body wave travels at roughly ____________ km/s.
  10. In the case of volcanic activity, the heat of _______ is overwhelmingly more important than any other source.
  11. Magma classified as MORB is most likely found in ____________ (geographic location).
  12. One of the two most abundant dissolved volatiles in magma is ___________.
  13. The only flood basalt with which humans have any experience erupted at _____________ (location and country).
  14. Stothers and Rampino postulated a periodicity of approximately ____ (number) million years for plateau basalt eruptions, magnetic field reversals and mass extinctions.
  15. The action of water, together with ____________ from the atmosphere is largely responsible for production of caves in limestone.
  16. Underground caves, stranded in the zone of aeration above a dropping water table, may lead to large circular depressions called ________________.
  17. All other things being equal, air density is lowest on a ______ (hot or cold) day.
  18. The most mass of the atmosphere is in the _____________ zone.
  19. The percentage of incoming radiation that is reflected by a natural surface is called _____________.
  20. Mount St. Helens erupted in 1980, emitting approximately _________ cubic kilometers of material from its magma chamber.

 

PART C

Answer any 3 of the following 5 questions. Each question is valued at 10 marks.

  1. (a) Earliest Earth had a greenhouse atmosphere loaded with CO2. Explain why that changed and where the CO2 went.                                                    [7]

(b) If major volcanic eruptions occurred nearly every year for a century, what might happen to global climate?                                                                [3]

  1. (a) Define latent heat.                                                                                        [4]

(b) Explain the sequence of events that turns an African storm into a hurricane hitting the east coast of North America.                                                          [6]

  1. Sketch a map of an idealized tectonic plate and evaluate the volcanic hazards along each type of plate edge.                                                                               [10]
  2. Explain how hot mantle rock can melt from (i) changes in temperature, (ii) changes in pressure, (iii) water content.                                                            [10]
  3. (a) Explain three ways that humans have caused or triggered earthquakes.          [6]

(b) What type of fault motion best characterizes the “Basin and Range” area of the western US states in this century?                                                                        [1]

(c) What Hawaiian volcanic processes cause earthquakes.                                 [3]

 

PART D

Write complete definitions of each of the following; use point form if you wish. Each question is valued at 3 marks.

  1. Supercell
  2. Kinetic energy
  3. Radioactivity
  4. Strain
  5. Farallon Plate
  6. Rodinia
  7. Aerolites
  8. Tektites
  9. Supernova
  10. Unconformity