Midterm exam 2
Tuesday, February 21, 2001
(1) Explain why winters in northern Europe are relatively mild, compared
to
locations at similar latitudes in Canada
and the northern United States.
(10 points)
(2) Explain how the biological pump in the oceans works. How does
it affect the
concentration of carbon dissolved in
sea water at the ocean surface? How does it
influence how limestone sediments on
the sea floor are distributed with respect to
the depth of the ocean? (15 points)
(3) Describe the role of weathering in the carbonate-silicate cycle.
What kind of
chemical transformation is involved?
What happens to the products of the
reaction? (10 points)
(4) Why do the atmospheres of Jupiter and Saturn contain so much more
hydrogen
(mostly in compounds like methane and
ammonia) than the Earth's atmosphere?
(10 points)
(5) How do we know that the climate of North Africa was more moist 2,000
years ago
than it is today? (10 points)
(6) Compare and contrast the Younger Dryas event, which occurred slightly
more
10,000 years ago and the last major
ice age, which was at its peak 20,000 years
ago. (10 points)
(7) Why aren't scientists concerned about the possibility that the burning
of
fossil fuels could seriously lower atmospheric
oxygen levels? (10 points)
(8) For each of the following kinds of proxy evidence, indicate the
time scale on
which it provides useful information
on past climate variability. (a) tree rings,
(b) 'redbeds' containing ferrous oxide
(c) ice cores (d) magnetic stripes, (e)
fossils. In answering the question
use the categories A lifetime of the earth, B
the past 100 million years, C the past
million years, D the past 20,000 years, and
E the past 2000 years. Note that
some kinds of proxy evidence provide useful
information on more than one time scale.
(9) In terms of the orbital theory of the ice ages, are present conditions
more or
less favorable for the growth of continental
ice sheets in the Northern Hemisphere
than conditions of 10,000 years ago or 10,000
years in the future? Explain your
answer. (Hint: focus on the distance
between the earth and the sun at various
points in its orbit). (10 points)
(10) Why do scientists ignore continental drift and orbital cycles in
making
predictions of climate change
during the 21st century? (5 points)