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.
- 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?
- 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?”
- 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.
- Our
Solar System formed roughly __________ billion years ago.
- Earth’s
Moon appears to have more impact craters than Earth because of its gravity.
________(True/False)
- Carbon-14
is produced from the cosmic bombardment of ___________ (name the isotope).
- The
‘champion’ of Catastrophism in the 18th Century was
________________
(name).
- The ‘most primitive meteorite ever recovered’
is the famous _______________ ___________________ meteorite (name).
- During
the _____________ Era, Rodinia fragmented and Pangaea assembled.
- In
1963 Vine and Matthews concluded a study which led to our understanding of
plate tectonics; the process they described is called ________________________.
- 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? _________________.
- A
compression seismic body wave travels at roughly ____________ km/s.
- 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 _____________________.
- The
Imamura-Iida Scale was developed in an effort to measure the severity of
__________________________.
- Name
one example of an active volcano. ____________________________.
- The
only flood basalt with which humans have any experience erupted at
__________________________________ (location
and country).
- Eruption
of the Siberian Traps correlates roughly with which mass extinction event?
_________________________ (give time
in millions of years).
- The
action of water, together with ____________ from the atmosphere is largely
responsible for production of caves in limestone.
- What
latitudes are most affected by changes in the tilt of Earth’s axis?
__________________ (equatorial,
polar, mid-latitude).
- All
other things being equal, air density is highest on a ______ (hot
or cold) day.
- The greenhouse
gases of the atmosphere are concentrated primarily in the __________________________
zone.
- The
percentage of incoming radiation that is reflected by a natural surface is
called _______________________.
- 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.
- 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]
- (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]
- Describe
the step-by-step process of the tsunami warning system that operates in
the Pacific Ocean. [10]
- (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]
- (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.
- Stratovolcano
- Kinetic
energy
- Pahoehoe
- Viscous
flow
- The
force of cohesion and friction
- Lahars
- Plinian eruption
- Fujita
scale
- Tropical
depression
- Complex
impact crater