THE UNIVERSITY OF WESTERN ONTARIO

LONDON                                           CANADA

Final Examination       -      Fall 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-spacing, go for it!). 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. You have been testing a sensitive gravity meter in a region of southern Ontario where the basement rock (highly folded and faulted crystalline Precambrian gneisses and schists of 700 million years old) is covered by about 10 meters of flat-lying Ordovician limestone of 500 million years of age. Your gravity survey has defined the outer limits of a perfectly circular depression immediately at the interface between limestone and basement rock; it measures 15 km in diameter. Having learned a great deal about impact craters in Earth Sciences 240A:

(a) What would you do (and what evidence would you look for) to prove that this is an impact crater? [Sorry, but while you have about $1Million budget, that’s not enough to excavate the limestone!]

(b) Can you make any conclusions about the object which made the crater?

(c) Can you tell even approximately when the crater formed?

(d) Would you expect to find any mass extinction evidence correlating with that event? Why?

  1. The current greenhouse debate is focused mainly on events of the 20th and 21st Centuries. From the point of view of an informed environmentalist (i.e. a ‘greenhouse proponent’), how would you reply to each of the following remarks made by ‘greenhouse skeptics’?

(a)    “Rising levels of greenhouse gases in the 20th Century have not caused Earth to warm”.

(b)   “It is arrogant of humans to think they are capable of altering Earth’s climate on a global scale”.

(c)    “Some areas have warmed very little or even cooled during the last 100 years, so how can you speak of ‘global’ greenhouse gas warming?”

  1. Scientists have been attempting to define earthquake and volcanic eruption hazards for many decades, with varying levels of success.

(a)    As a resident of Vancouver, how would you rate the possibility of each of these two natural processes occurring within the next 100 years (very weak, weak, moderate, strong, very strong)?

(b)   What is the single strongest geologic evidence upon which you based the time-probability assumption of an eruption? Of an earthquake?

(c)    Pick either earthquakes or volcanic eruptions and list the factors by which scientists determine that an imminent event is predicted anywhere in the world (i.e. you are not limited to Vancouver for this part).

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. Our Solar System formed roughly __________ billion years ago.
  2. Earth’s Moon appears to have more impact craters than Earth because of its gravity. ________(True/False)
  3. Carbon-14 is produced from the cosmic bombardment of ___________ (name the isotope).
  4. The ‘champion’ of Catastrophism in the 18th Century was ________________

(name).

  1. The ‘most primitive meteorite ever recovered’ is the famous _______________ ___________________ meteorite (name).
  2. During the _____________ Era, Rodinia fragmented and Pangaea assembled.
  3. In 1963 Vine and Matthews concluded a study which led to our understanding of plate tectonics; the process they described is called ________________________.
  4. Since subduction ceased along much of the USA west coast, the Basin and Range region developed as a result of what type of fault motion? _________________.
  5. A compression seismic body wave travels at roughly ____________ km/s.
  6. If a major earthquake were to strike a major city such as San Francisco, the worst time of day for that to happen would be _____________________.
  7. The Imamura-Iida Scale was developed in an effort to measure the severity of __________________________.
  8. Name one example of an active volcano. ____________________________.
  9. The only flood basalt with which humans have any experience erupted at __________________________________ (location and country).
  10. Eruption of the Siberian Traps correlates roughly with which mass extinction event? _________________________ (give time in millions of years).
  11. The action of water, together with ____________ from the atmosphere is largely responsible for production of caves in limestone.
  12. What latitudes are most affected by changes in the tilt of Earth’s axis? __________________ (equatorial, polar, mid-latitude).
  13. All other things being equal, air density is highest on a ______ (hot or cold) day.
  14. The greenhouse gases of the atmosphere are concentrated primarily in the __________________________ zone.
  15. The percentage of incoming radiation that is reflected by a natural surface is called _______________________.
  16. The event which poured a cold water ‘lid’ over the North Atlantic some 12,000 years ago is called _____________________________________(Proper Name).

 

PART C

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

  1. Explain the eruptive behaviour of a plume-fed volcano on a continent. You need to include a consideration of magma characteristics and evolution, and stages of eruption.                                                                                                      [10]
  2. (a) Where did the extra CO2 from Earth’s early atmosphere go? How did it get there?                                                                                                               [6]

(b) Where does most of the current CO2 produced by humans go?                    [2]

(c) Which reservoir has the most C: atmosphere, vegetation, rocks, ocean? [2]

  1. Describe the step-by-step process of the tsunami warning system that operates in the Pacific Ocean.                                                                                          [10]
  2. (a) Use a sketch plus words to explain elastic rebound as far as faults are concerned.                                                                                                   [5]

(b) Evaluate the earthquake hazards in locked versus creeping segments of the same fault system.                                                                                               [5]

  1. (a) Explain how a ‘mass extinction’ event differs from a simple ‘extinction’

event.                                                                                                               [3]

(b) Evaluate the correlation of mass extinctions with (i) impact events and (ii) flood basalt events.                                                                                                [7]

 

PART D

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

  1. Stratovolcano
  2. Kinetic energy
  3. Pahoehoe
  4. Viscous flow
  5. The force of cohesion and friction
  6. Lahars
  7. Plinian eruption
  8. Fujita scale
  9. Tropical depression
  10. Complex impact crater