c division dynamic planet sont test question document part 1: interpretation … · 2019-11-29 ·...

C Division Dynamic Planet SONT Test Question Document

Part 1: Interpretation of Alpine Features on Topographic Maps

Use the USGS Maroon Bells topographic map (Figure 1) to answer these questions.

1. What is the contour interval (in feet) on Figure 1? (2) 2. Which is the highest peak shown? (1)3. What is the lowest elevation (in feet) on Figure 1? (2)4. What is the ground length (in feet) of the line from A to A’ ? (2)5. What is the fractional scale of the map? (2)6. is map shows a glaciated region in the Rocky Mountains. What was the direction of ice

flow at point F? (2)7. Which lake is in the foreground of the photo below? (2)8. What do you think the dashed line in the southwest portion of the map represents? (2)9. Are the majority of the glacial features shown on the map the result of erosional or

depositional processes? (1)10. Match the features labeled B through F on the map with the appropriate names on the

answer sheet. Only 5 of the names will be used! (10)11. Draw a longitudinal profile of the land on the line between A and A’. Start your profile at

the north end of the black line and end it at the south end of the line. Plot at least 8 elevation points! Be sure to label your axes completely. (10) Tiebreaker #1

12. What is the vertical exaggeration of the longitudinal profile? (2)

13. Based on your profile, which end of the cross-section is steeper (N or S)? (1)

14. Describe the shape of the valley in the longitudinal profile (1)

15. e sloping feature marked G is a ____________. (1)

Do not write your answers on this document. They will not be scored. Write all your answers on the Answer document.

Questions 1

Part 2 - Interpretation of Lowland Features on Topographic Maps

Use the USGS Oswego East topographic map (Figure 2) to answer these questions.

16. What is the contour interval (in feet) on Figure 2? (2)17. is map shows a glaciated region in upstate New York. It is classified as a fluted

landscape. It is dominated by features known as ______. (2)18. ese features almost always appear together in large numbers. What is a group of them

called? (2)19. Are these features the result of erosional or depositional processes? (1)20. Five of these features (including Deer Ridge) are identified on the map along with lines

that trace their longitudinal axes. Use a protractor to measure the orientation of each of these axes. Report your answers as bearings in degrees off of due North (e.g., North 42° East or N42E). (10)

21. Based on your results, was the ice flow in this region convergent or divergent? (1)22. Which end of these features is steeper (N or S)? (1)23. Which is the stoss end, and which is the lee? (2)24. Which direction was the ice flowing towards during the last phases of the glaciation that

formed this fluted landscape? (3)25. Only a few miles north of this area is one of the Great Lakes. Which one? (2)26. How are the Great Lakes basins related to glaciers and to rock hardness? (5)27. e glacier that formed this landscape was not an alpine glacier, it was a _________.(2)28. What was the driving force behind the movement of the ice that formed this landscape?

(2)29. What was the approximate thickness of the ice in this region? (2)

a. 200 - 400 metersb. 800 - 1200 metersc. 2000 - 3000 metersd. 5000 - 8000 meters

30. e weight of the ice on the land was enormous. Even though the ice was gone over 12,000 years ago, the land is still recovering in a process known as ____________ . (3)


Questions 2

Part 3: Glacier Mass Balance and Climate

31. Match the following to the letters on this diagram of an alpine glacier: equilibrium line, zone of ablation, zone of accumulation. (3)

32. On the diagram above, which direction will the ice move if ablation exceeds accumulation (to the right or le)? (1)

33. On the diagram above, which direction will the ice move if accumulation exceeds ablation (to the right or le)? (1)

34. On the diagram above, which direction will the terminus move if ablation exceeds accumulation (to the right or le)? (2)

35. Examine the map below showing the terminus of a glacier at three points in time. A line of stakes was driven into the surface of the ice in 1954 (marked 1) on the map. Over time, the glacier moved the stakes. Which of the other lines (A through F) best represents the position of the stakes in 1960? (4) Tiebreaker #2


Questions 3

AB

CGlacier

West East

Initial line(1)

1960terminus

D E F

A B C

1954 terminus

1948 terminus

Part 3 - continued: Glacier Mass Balance and Climate

Examine Figure 3 for Questions 36 through 41.

36. What is the overall relationship between latitude and glacier length for this sample? (3)37. What is the overall pattern of change in glacier length worldwide since 1900? (2)38. Which glacier has the longest period of record? (2)39. How many kilometers did the Paierl glacier lose in the period of record? (2)40. Which glacier lost the least length overall in percentage terms from 1900 to 2000, and how

much did it lose (in percent)? (5)41. Which glacier experienced the greatest percentage increase in length prior to 1900? (2)42. According to the graph, in which time period has there been the most lost of glacier

length worldwide? (2)a. 1900 - 1920b. 1940 - 1960c. 1960 - 1980d. 1980 - 2000

Examine Figure 4 to answer Questions 43 to 50.

43. For most of the years between 1946 and 2006, the Taku glacier’s annual balance has been net accumulation or net ablation? (1)

44. In what year did the largest balance occur? (1)45. What was the annual balance in 1997? (2)46. From 1958 to 1988, what was the general cumulative balance trend? (1)47. From 1958 to 1988, what was the average rate of accumulation or ablation? (4)48. In what year was the ELA the lowest value? (1)49. Describe the relationship between ELA and annual balance shown in the figure. (2)50. Explain the climatological reason for the relationship between ELA and annual balance (4)

Tiebreaker #3


Questions 4

Part 3 - continued: Glacier Mass Balance and Climate

51. Glacial ice has a density of around 0.92 g/cm3. Newly fallen snow has a density of around 0.06 g/cm3. What depth of snow is necessary to form a 367 meters of glacial ice? (4)

52. What is removed from the snow pack to form glacial ice? (2) 53. Tidewater glaciers may afloat at their terminus. If sea water has a density of 1.04 g/cm3,

how deep must the water be to float 127 m of glacial ice? (4)

Examine Figure 5 to answer Questions 54 to 61.

54. How many months are in a glaciological year? (2)55. Why is the glaciological winter longer than the glaciological summer? (4)56. During which glaciological season is there a positive mass change? (2)57. e fastest accumulation rate occurs during: (2)

a. early winterb. late summerc. mid winterd. late winter

58. What event on the mass balance curve triggers the onset of glaciological summer? (4)59. Which of these is the best interpretation of the ablation curve in the summer? (2)

a. it is asymptoticb. summer ablation is not as rapid as winter accumulationc. the rate of ablation declines as the summer progressesd. the rate of ablation is nearly constant

60. What is summer accumulation? (2)61. By the end of the year depicted, did the glacier advance or retreat? (1)

62. Consider a glacier in the process of depositing an end moraine over a time span of several decades. What can you say about the overall net mass balance of this glacier? (4) Tiebreaker #4


Questions 5

Part 4: Glacial Flow

63. Ideally, where on a glacier would you find the maximum velocity of flow, assuming no change in width? (2)a. Where accumulation most exceeds ablationb. At the equilibrium linec. Where the ice is thickestd. At the terminus

64. On the Answer Sheet, sketch a typical vertical ice velocity profile, assuming no basal sliding. (6)

65. On the Answer Sheet Page 8, draw arrows from each red dot (see the example) indicating the direction of ice flow on the map of an ice field in Alaska. (8)

66. On the same map, find the box on the Hidden Glacier. Place the letter F (for fast) inside the box where you expect a zone of higher flow rate, and the letter S (for slow) in a zone of lesser flow rate. (2)

67. On the same map, place a large asterisk in one of the areas from which ice flow diverges in more than one direction. (4)

68. On the Taku Glacier, the basal velocity can be calculated according to this formula:

M. S. Pelto et al.: Equilibrium flow of Taku Glacier, Alaska 155

Fig. 9. Surface elevation of stations along Profile IV and seismically determined bottom topography along the profile, Taku Glacier, Alaska.

Profile IV. These values are beyond that at which substantialbasal sliding would be anticipated. In addition, the consis-tency in velocity each summer and in annual velocity indi-cates that there is negligible seasonal fluctuation in velocityin the vicinity of Profile IV. Seasonal fluctuations are gener-ally the result of changes in sliding.To determine depth average velocity (Ud) we have applied

the Eq. (1)(van der Veen, 1999; Nick et al., 2007), using val-ues from the center of the glacier.

Ud = 2A H

n + 2Sn

d (1)

where A=4.6⇥10�10 kpa�3 day�1 is the rate factor (Pater-son, 1981), n=3 is the flow-law exponent, H is the measuredice thickness (1400m) and Sd the basal shear stress notedabove (125–180 kpa)(or basal drag). Plugging these valuesinto Eq. (1) gives

Ud = (2)(4.6⇥ 10�10 kpa�3 day�1)(1400)/5⇥ (1203)

= 0.45mday�1 (2)

The lower value for basal shear stress is used at the sugges-tion of van der Veen (1999) since part of the driving stressis likely balanced by lateral drag. We then use the calcu-lated value of Ud to calculate Us from Eq. (3) (van der Veen,1999):Plugging the calculated Ud velocity into Eq. (3) gives the

surface velocity in Eq. (4)

Us = n + 2n + 1

Ud = 1.25Ud (3)

Us = 0.56mday�1/1.25 = 0.45mday�1 (4)

Us of 0.56m day�1 is an excellent agreement with the ob-served surface velocity of Us=0.6m day�1. This suggests

that it is reasonable to use Eq. (3) to determine Ud for eachincrement of glacier width.The mean Us velocity between each two survey flags is

used to represent the average Us for that width increment ofthe glacier. The mean depth for that width increment fromthe seismic profile is then determined. The product of thewidth of the increment and depth of the increment providethe mean cross sectional area. The mean Us for each incre-ment is converted to a mean Ud using Eq. (3).The volume flux was determined separately for paral-

lel survey lines along Profiles IV (upper line and lowerline). For Profile IV, 29 km above the terminus, the ex-pected volume flux, based on surface flux observations, was5.50⇥108 m3 a�1 (±10%), the volume flux range was 5.00–5.47⇥108 m3 a�1, with a mean of 5.25⇥108 m3 a�1 for theupper line and 5.27⇥108 m3 a�1 for the lower line (Table 1).This indicates a slightly positive balance and glacier thick-ening above Profile IV for the 1950–2006 period, which iscorroborated by field observations (Welsch and Lang, 1998)and laser altimetry (Arendt, 2006; Larsen et al., 2007). Thethickness change observations are in the range of expectedvalues for the observed positive surface mass balance, thesame conclusion that Nolan et al. (1995) reached. The cal-culated volume flux is based on the 1950–2006 average massbalance profile for the glacier and not for a given year. Thesurface flux during recent negative balance years would ob-viously give a lower surface flux value and in fact the surfaceelevation in the vicinity of Profile IV has not been increasingsince 1993.

www.the-cryosphere.net/2/147/2008/ The Cryosphere, 2, 147–157, 2008

A is a rate factor (4.6 x 10-10 kpa -3/day), n is the flow-law exponent (n = 3), H is the thickness of the ice (1400 m), and Sd n is the basal shear stress (120 kpa) raised to the power of n (n = 3). Use this formula to calculate the velocity of flow in meters per day (4).

69. Now calculate the surface velocity using this formula (2):

M. S. Pelto et al.: Equilibrium flow of Taku Glacier, Alaska 155

Fig. 9. Surface elevation of stations along Profile IV and seismically determined bottom topography along the profile, Taku Glacier, Alaska.

Profile IV. These values are beyond that at which substantialbasal sliding would be anticipated. In addition, the consis-tency in velocity each summer and in annual velocity indi-cates that there is negligible seasonal fluctuation in velocityin the vicinity of Profile IV. Seasonal fluctuations are gener-ally the result of changes in sliding.To determine depth average velocity (Ud) we have applied

the Eq. (1)(van der Veen, 1999; Nick et al., 2007), using val-ues from the center of the glacier.

Ud = 2A H

n + 2Sn

d (1)

where A=4.6⇥10�10 kpa�3 day�1 is the rate factor (Pater-son, 1981), n=3 is the flow-law exponent, H is the measuredice thickness (1400m) and Sd the basal shear stress notedabove (125–180 kpa)(or basal drag). Plugging these valuesinto Eq. (1) gives

Ud = (2)(4.6⇥ 10�10 kpa�3 day�1)(1400)/5⇥ (1203)

= 0.45mday�1 (2)

The lower value for basal shear stress is used at the sugges-tion of van der Veen (1999) since part of the driving stressis likely balanced by lateral drag. We then use the calcu-lated value of Ud to calculate Us from Eq. (3) (van der Veen,1999):Plugging the calculated Ud velocity into Eq. (3) gives the

surface velocity in Eq. (4)

Us = n + 2n + 1

Ud = 1.25Ud (3)

Us = 0.56mday�1/1.25 = 0.45mday�1 (4)

Us of 0.56m day�1 is an excellent agreement with the ob-served surface velocity of Us=0.6m day�1. This suggests

that it is reasonable to use Eq. (3) to determine Ud for eachincrement of glacier width.The mean Us velocity between each two survey flags is

used to represent the average Us for that width increment ofthe glacier. The mean depth for that width increment fromthe seismic profile is then determined. The product of thewidth of the increment and depth of the increment providethe mean cross sectional area. The mean Us for each incre-ment is converted to a mean Ud using Eq. (3).The volume flux was determined separately for paral-

lel survey lines along Profiles IV (upper line and lowerline). For Profile IV, 29 km above the terminus, the ex-pected volume flux, based on surface flux observations, was5.50⇥108 m3 a�1 (±10%), the volume flux range was 5.00–5.47⇥108 m3 a�1, with a mean of 5.25⇥108 m3 a�1 for theupper line and 5.27⇥108 m3 a�1 for the lower line (Table 1).This indicates a slightly positive balance and glacier thick-ening above Profile IV for the 1950–2006 period, which iscorroborated by field observations (Welsch and Lang, 1998)and laser altimetry (Arendt, 2006; Larsen et al., 2007). Thethickness change observations are in the range of expectedvalues for the observed positive surface mass balance, thesame conclusion that Nolan et al. (1995) reached. The cal-culated volume flux is based on the 1950–2006 average massbalance profile for the glacier and not for a given year. Thesurface flux during recent negative balance years would ob-viously give a lower surface flux value and in fact the surfaceelevation in the vicinity of Profile IV has not been increasingsince 1993.

www.the-cryosphere.net/2/147/2008/ The Cryosphere, 2, 147–157, 2008


Questions 6

*

Part 5: Glacial History

70. True or False: e amount of solar radiation received by the Earth as a whole is unchanged by orbital variations, but the amount received in different places at different seasons changes significantly. (2)

71. About 300 million years ago, major parts of Africa and India were glaciated, but not Canada and the Northern U.S. Why not? (2)

72. During what time interval of Earth’s history have the most recent ice sheets formed? (2)a. Permian d. Plioceneb. Pleistocene e. Proterozoicc. Paleozoic

73. During what time interval of Earth’s history can evidence of a completely ice-covered “snowball Earth” be found? (2)a. Permian d. Plioceneb. Pleistocene e. Proterozoicc. Paleozoic

74. During a glacial advance, what happens to sea level? (2)75. During a glacial advance, what happens to the ratio of 18O to 16O in the world’s oceans? (2)

Examine Figure 6 to Answer Questions 76 to 80

76. What are the North American names given to the time periods marked 1 and 2? (4)77. What are the gray shaded time periods known as? (2)78. Which orbital variation has the closest correlation with the pattern of glacial advance and

retreat? (2)79. What is the relevance of summer Solar Forcing at 65°N on Figure 6? (4) Tiebreaker #580. Other than orbital variations, name up to three other important influences on glaciation

during Earth’s history. (6)


Questions 7

Part 5 - continued: Glacial History

Refer to Figure 7, “End Moraines of the Wisconsin Glacial Episode” to answer the remaining questions.

81. In Illinois, almost all of the ice that invaded the state flowed out of what major basin? (2)82. In Illinois, there are at about 10 distinct till units that were deposited during the most

recent glacial advance. What are two characteristics that distinguish glacial till from other unconsolidated deposits? (4)

83. e 10 till units deposited by the ice have distinct colors, textures, and mineral composition. What is the cause of these changes? (2)

84. In Illinois, the youngest till unit is called the _______________ till. (2)85. e oldest till on this map is the ___________ till: (2)

a. Sniderb. Tiskilwac. Delavand. Fairgrange

86. Name two tills that cannot be age sorted relative to each other, based solely on the map. (4)

87. Name one till unit that was deposited by ice that partially over-ran a previously existing moraine. (2)

88. What is the difference between an end moraine and a recessional moraine? (2)89. Name a recessional moraine that is composed of Yorkville Till. (2)90. e Iroquois Moraine is uncolored. It was formed by a completely different lobe of ice

originating in what basin? (2)


Questions 8

c division dynamic planet sont test question document part 1: interpretation … · 2019-11-29 ·...

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