Homework Questions for Lecture 15
ES 1000
Use these questions to test your knowledge of Lecture 15.
A. Short answer:
1. A moving body of ice that forms from the accumulation and
compaction of snow is called a ____________.
2. Glaciers flow downslope or outward under the influence of ________.
3. __________ is the packed snow that survives a summer melting
season.
4. __________ glaciers are confined by surrounding mountains
5. __________ glaciers create and occupy semicircular basins on
mountainsides, usually near the heads of valleys.
6. __________ glaciers flow in pre-existing stream valleys.
7. A _____________ glacier originates as a confined alpine glacier but
flows onto adjacent lowland where, unconfined, it can spread rapidly.
8. A piedmont glacier that reaches seawater is a ____________ glacier.
9. The only completely unconfined glacier is a ____________ ice sheet.
10.In the zone of _________________ more snow is added every year
than is lost.
11.______________ is the process by which chunks of ice are broken off
by wave or tidal action; it is the source of icebergs.
12.A glacier's _______ is measured by accumulation minus ablation.
13.Although the _______ of a glacier may be advancing, receding, or
remaining stationary, an alpine glacier is always flowing downhill.
14.In internal ________________, a glacier's ice crystals deform under
pressure from overlying ice and slip past one another.
15. In __________ sliding, warmer glaciers thaw at their bases,
producing a film of water on which it slides.
B. Match the Terms.
1. Firn _____
a. all glacial deposits
2. Glacier's budget ____
b. seawater floods glacial valley
3. Ablation ____
c. accumulation minus ablation
4. Cirque____
d. makes icebergs
5. Esker ____
e. abrade upglacier, quarry downglacier
6. Till _____
f. semicircular basin on mountainside
7. Drumlins_____
g. loss of snow and ice
8. U-shaped ______
h. dense, well-packed snow
9. Drift ______
i. adjacent glaciers merge
10. Medial moraine ____
j. film of water at base.
11. Calving _____
k. sinuous meltwater deposit under glacier
12. Fjord _______
l. glacial valley shape
13. Roche Moutonée ____
m. ice sheets override moraines.
14. Basal sliding ______
n. drift deposited directly from glacial ice.
15. Tarn _____
o. cirque lake
C. True or False? Circle the correct answer.
1. Glacial ice carrying coarser rock fragments can cut long striations, or
scratches, into the bedrock surface. These markings are oriented in the
same direction as the ice flow. True or False?
2. Glacial quarrying occurs when a glacier lifts masses of bedrock
dislodged by frost wedging. True or False?
3. Drumlins are deep semicircular alpine basins created by glacial
abrasion and quarrying. True or False?
4. When cirque glaciers melt, a cirque lake or tarn forms in the basin.
True or False?
5. Valleys carved out by steep rivers are U-shaped; glaciated valleys are
V-shaped. True or False?
6. When seawater submerges a glaciated valley it forms a deep,
saltwater-filled fjord. Their existence reflects the rise of sea level
associated with melting after the last ice age. True or False?
7. Examples of deep U-shaped troughs formed by continental ice sheets
are the Finger Lakes, Great Lakes, and Loch Ness. True or False?
8. If the terminus of a glacier is stationary, a moraine continues to
accumulate at the terminus. True or False?
9. When a glacier recedes for the final time, it leaves a terminal moraine
marking the farthest advance of ice. True or False?
10.Outwash is deposited downstream of the glacial terminus by braided
streams. True or False?
11.Loess are deposits of silt carried by wind from exposed, drying
outwash. True or False?
12.Sinuous ridges formed beneath the ablation zone are called eskers.
True or False?
13.Near continental ice sheets, ice dams can alter drainage patterns. True
or False?
14.Widely contrasting air temperatures near glaciers cause abnormally
cloudy, cool, rainy weather. True or False?
15.Decreased sea levels, caused when water is trapped in polar ice sheets,
extends coastlines and exposes land bridges. True or False?
16.Ice Ages alternate between Glacial periods and Interglacial periods.
True or False?
17.Two requirements for glaciation are sizable landmasses at or near the
poles and land surfaces with relatively high elevation. True or False?
18.The Earth's glacial past is evident from old Tillites, moraines and
eskers, and from glacial striations on bedrock. True or False?
19.The Pleistocene Epoch glaciation is the most recent geological time in
which major ice ages occurred. True or False?
20.During Interglacials, temperatures were similar to current
temperatures. True or False?
D. Multiple choice:
1) In a confined glacier, the ice of a glacier advances downslope under
which conditions?
a) Accumulation is greater than ablation.
b) Accumulation is less than ablation.
c) Accumulation and ablation are equal.
d) All of the above.
2) The glacier’s zone of accumulation can be recognized by:
(a) icebergs calving into a lake.
(b) snow from the previous winter covering the glacier ice.
(c) exposed, bare ice.
(d) rocks and boulders melting from the ice.
3) In the alpine highlands of North America, Europe, and Asia, the most
effective geologic shaping process would be:
(a) mass-movement.
(b) wind erosion.
(c) stream erosion.
(d) erosion by glaciers.
4) The difference between a cirque and a tarn is:
a) a cirque is at the zone of accumulation while a tarn is at the zone of
ablation.
b) a cirque is a basin made by a glacier while a tarn is a lake within a
cirque.
c) a cirque is a basin made by a glacier while a tarn is a mountain pass
between two cirques.
d) a tarn is a basin made by a glacier while a cirque is a sharp ridge
between two tarns.
5) A submerged U-shaped valley is called a:
a) col.
b) hanging valley.
c) fjord.
d) arête.
6) The term “glacial drift” applies to:
a) all glacial deposits, collectively.
b) glacial deposits of very fine particles that eventually become windblown.
c) glacial deposits that are carried by meltwater into nearby streams.
d) the redistribution of glacial deposits by consecutive advances.
7) Till appears different from outwash in that:
a) till contains only smaller particles while outwash contains both small
and large rock fragments.
b) till is darker in color than outwash.
c) till is better sorted and better stratified than outwash.
d) till is less sorted and less stratified than outwash.
8) A terminal moraine forms when:
a) accumulation is less than ablation.
b) accumulation is greater than ablation.
c) accumulation and ablation are equal.
d) All of the above.
9) A medial moraine forms:
a) along the sides of a glacier.
b) where two valley glaciers merge.
c) where a glacier terminus advances beyond a recessional moraine.
d) beneath a glacier in a sinuous ridge.
10) Loess is a soil formed by:
a) meltwater deposits of sand and gravel.
b) glacial advances over previously deposited moraines.
c) a mixture of sand and clay at the bottom of a meltwater lake.
d) wind-blown deposits of outwash silt.
11) During major glaciations, sea level was 130 meters lower than at
present, facilitating land migration between:
a) Africa and South America.
b) Europe and North America.
c) North America and Asia.
d) Asia and Australia.
12) The term “albedo” refers to:
a) the percentage of solar radiation that is reflected away from the
Earth’s surface.
b) the percentage of solar radiation that is absorbed by the Earth’s
atmosphere.
c) the percentage of solar radiation that reaches the Earth’s surface.
d) the percentage of solar radiation that is absorbed by the Earth’s
surface.
13) Which of the following describe the most recent extensive glaciation in
North America:
a) the ice sheet stretched the full breadth of southern Canada and the
northern United States.
b) the ice sheet stripped regolith 15–25 meters deep from regions of
Canada and the United States.
c) a warming trend began 18,000 years ago that ultimately brought the
glacial period to an end.
All of the above
E. Short answers
1. Explain the various factors that result in huge continental glaciers. Be sure
to include:
a. How does plate tectonics contribute to the initiation of an ice age?
b. Why is it important to have land in Polar Regions?
c. What is albedo?
d. What is the role of the Earth’s orbit around the Sun?
e. Why is the tilt of Earth’s spin axis, and the wobble of the spin axis,
important?
f. Referring back to the previous lecture, what is the role of currents in
warming Polar Regions?
F. Calculations Exact Binomial Goodness of Fit.
You use the exact binomial test when you
have one nominal variable with only two values
(such as male vs. female, heads vs. tails).
P(Success = k) =
n!__
k! (n-k)!
pk q (n-k)
Gregor Mendel crossed pea plants that were "heterozygotes" for Green pod/yellow pod.
"Heterozygotes" means one parent plant provided the G "allele" for Green pod, and the
other parent provided the g "allele" for yellow pod. An allele is a variety of a gene, like
blue eyes or brown. The heterozygote parents are labeled on the chart above. Possible
combinations of their genes in their progeny are shown in the rectangle. The possibilities
are: a G from the mother and a G from the father, a G from the mother and a g from the
father, a G from the father and a g from the mother, and g from both parents. Each
possibility occurs 1/4 of the time.
If the pea plant received G alleles form both parents (GG), the pod is green. Even if only
one Green allele is present, e.g. Gg or gG, the pod is green. The first three progeny types
have green pods, so green pod occurs 1/4 +1/4 + 1/4 = 3/4 of the time (75%). Since only
one copy of G is necessary for a normal appearance, we say the Green allele G is
Dominant, and the broken yellow allele g is recessive. The pod is yellow only if it has the
defective allele from both parents, and is therefore gg, so 25%.
You decide to test Mendel’s claim. You cross two heterozygote plants, and get 17 Green
and 3 yellow pod "offspring" plants, for a total of 20 pea plants. H0: there is no
significant difference between the observed and expected frequencies of pea plants with
Green pods. The expected numbers of plants under the null hypothesis are 75% = 15
Green and 25% = 5 yellow pods, so you observed slightly more Green-pod plants than
expected. Is Mendel’s null hypothesis “no significant difference from 75% Green and
25% yellow” correct?
We don't need a critical value table because we can calculate this ourselves. n=20, k=17
P (Green = 17 out of 20) = ___20!____(0.75)17 * (0.25)3
17! *3!
Remember that 20! = 20*19*18* …*3*2*1 for example, and 17! is 17*16* …*3*2*1
so most of the left side cancels. My calculations show this equals 1140 *.0075 *.0156 =
0.13338, a result that can occur more than more than 13% of the time if the null
hypothesis 75% Green and 25% yellow is correct.
A "significant difference" is a result that occurs less than one time in 20 trials, i.e. a probability of
P = 0.05 or less. Since our experiment showed a more common result P = 0.13 we (choose one:
accept the null hypothesis / reject the null hypothesis)