An Imbalance in Accumulation and Ablation - Report Example

3. Gravity, along with the friction resulting from an imbalance in accumulation and ablation causes the flow of ice. Since the friction occurs more between the lower layers of ice and the bedrock, the flow of ice is highest at the walls and the floor of the glacier. 4. a. 4. b. Greenland, Keewatin and Labrador centers. 4. c. 4. d. 4. e. In Figure 17.4 (a), the zone of accumulation is the point marked at 4000 m on the East Antarctic Ice sheet. In Figure 17.4 (b), the Greenland, Keewatin and Labrador centers constitute the zones of accumulation. In Figure 17.4 (c), the zones of accumulation include the northern Europe, Greenland and most of the British Isles. 4. f. In Figure 17.4 (a), the zones of ablation are the points where the West Antarctic ice sheet meets the Bellingshausen Sea and the Amundsen Sea. On the other side, the East Antarctic ice sheet meets the Amery ice shelf and the Ross Ice Shelf as the zones of ablation. In Figure 17.4 (b), the zones of ablation are encountered in the form of sea ice near the central parts of North America and the borders of the northern parts. In Figure 17.4 (c), Moscow, Berlin, Warsaw in the European region and the London in the British Isles are the zones of ablation. 5. a. Alpine, erosional, polythermal glacier. 5. b. 5. c. In the above photographs which were taken in 1958 and 2003 respectively, we can see the difference in the terminus of the McCall glacier. The shortened terminus in the recent photograph is due to the rapid loss of ice in the glacier. Studies suggest that this loss of ice began during late 1800s. Radiation is the main reason behind the melting of ice. The glacier is completely deprived of sunlight during summer when the neighboring mountains block the sunlight. This leads to radiation imbalance. Moreover, the mass balance of the glacier has been consistently negative. The mass balance of the glacier was measured by placing a number of accumulation or ablation stakes on the glacier. This loss of mass can also be proven with the help of the outgoing ground water. Most of the outgoing water refroze after sometime and formed huge perennial aufeis deposits. These additional growths can be used to predict a change in the mass of the glacier. 5. d. Ablation. 5. e. Warming in the Arctic region has caused the ice temperature of the glacier to go up significantly, resulting in thinning of the glacier and the retreat of the terminus. The seasonal input of meltwater and low temperatures have been found to result in the formation of a dense layer of cold ice over a thin, sparse layer of temperate ice at the base. Considering that the temperature of the glacier is more at the bottom, this factor might be causing the extremely fast ablation at the lower levels. 5. f. Finger lake. 5. g. Drumlins and Till. 6. a. The steep-sided valleys were formed due to erosion caused by a superior glacier and by the Lituya Bay which is an inlet of the Gulf of Alaska. The north and south glaciers are said to be the remnants of this great glacier. 6. b. When arranged in a stereoscopic fashion, the glacier at the right appears to be at a lower elevation. This is because the image at the left hand side focuses more on the terminus of the glacier. 6.c. The dark stripes on the glacier get their color due to interaction with morainal rubble. These dark stripes indicate that the glacier had come in contact with a moraine while flowing through. This could be because of an advance of the glacier or the accidental fall of any substance from the valley wall which later mixed with the water formed from the melting ice and eventually took the form of moraines. 6. d. The medial moraine is a ridge formed when two glaciers clash 6. e. Since the crevasses appear at the end of the glacier in high concentration, several crevasses intersect at the end forming ice pinnacles. 6. f. The sides show the stratification or the layering of the underlying rocks. In this image, we can see that the steep walls of the cliff come to an abrupt end suggesting that the glacier was once longer and thicker. 6. g. 6. h. The Gulf of Alaska. The shoreline on the northeast side is steeply sloping. 6. i. The crevasses are near the delta because the delta is a result of active deposition occurring from crevasses. 6. j. The figures 17.7 b and 17.8 show sedimentary deposits of a continental glacier. 7. a. 7. b. The floor of the Yosemite Valley is flat and the valley is a broadened part of the canyon of the Merced River. The roughly parallel sides rise up to 4,000 feet and stop at the foot of the cliffs which reach up to another 4,000 feet. The valley narrows considerably at El Capitan and the Cathedral Rocks and is relatively wider in other places. The head of the valley is marked with the presence of Half Dome. True to its name, it is a rock structure which is smoothly shaped on three sides. However, the side which faces the valley is steeply sloping and continues the skyward straight line of the walls of the valley. 7. c. Studies have stated that, about 10 million years ago, a small valley was tilted westward accelerating the flow of Merced River and its tributaries. As the river cut deeper through the valley, it widened the valley and gave birth to the first forests of the valley. About 30,000 years ago, the Tioga glaciations further enlarged the valley. 7. d. The Yosemite Valley is 7 miles in length and 1 mile in width. The floor is flat and the valley is a widened part of the canyon of the Merced River. The sides are roughly parallel and rise up to 4,000 feet. At this point, several cliffs reaching up to 4,000 feet can be found. The valley narrows down at El Capitan and the Cathedral Rocks and is relatively wider in other places. The Half Dome rock structure marks the head of the valley. True to its name, it is a rock structure which is smoothly shaped on three sides. However, the side which faces the valley is nearly vertical and continues the skyward straight line formed by the walls of the valley. 7. e. No. Though the steeper side of Half Dome looks like a continuation of the walls of the valley, the slope is slightly different. 7. f. The orientation of the major features of the valley is determined by the regional-scale joints. Other features which share such attributes are the parallel cliffs at Cathedral Rocks and the Westward sloping faces of the three brothers. 8. a. 1. Moraines and glacial formations. 2. Glacial pools. 3. Retreated glaciers. 4. The last surviving glacier above Anchorage. 5. Denali glacier. 6. Matanuska glacier. 7. Portage glacier. 8. Eklutna glacier. 9. Dome flow complex at the Power line pass. 10. Turn around arm along with glacial valleys, hanging valleys, till and silt. 8. b. 8. c. 9. a. Upper Pleistocene age (Pinedale age): ml, Qa­, Qo, Ql, Qt, Qr, Qp, Upper Pleistocene age (Bull lake age): Qb Pleistocene age (pre-Bull lake age): Qpb, Tl, Ysp 9. b. Cenozoic. 9. c. Crest of a glacial moraine: . 9. d. The construction of a dam against the Grand Lake under the Colorado-Big Thomson project resulted in the birth of the Shadow Mountain Lake, which is an artificial lake that gets water from the Lake Granby. 9. e. Before the Colorado-Big Thomson project, the place now known as the Shadow Mountain Lake was a broad valley through which the Colorado River headwaters flowed. And the islands we now see at the southern ends of the Shadow Mountain Lake were terminal moraines created by a massive glacier. Moreover, unlike the shallow lakes created by the advance and retreat of glaciers, the Grand Lake is deep. All these factors, along with the frequent backward pumping of water from the Lake Granby to the Shadow Mountain Lake will damage the moraines in this area in case of glacier advancement. The Shadow Mountain Lake is the younger of the two. 9.f. Since any glacial deposit is said to be well sorted if it consists of grains of equal size, the material making up the till in these moraines are well sorted. And the type of moraine depicted in the map is terminal (?). 9.g. 9. h. 9. i. 10. a. The image is not clear so I could not read the map. However, these are the famous glacial features found in Rochester, NY: Finger Lakes, Lake Ontario, Mendon ponds, Mt. Hope, hills of Highland Park, Pinnacle Hill etc. 10. b. A continental glacier. 10. c. 10. d. 11. a. Blue Ridge is a glacial feature in Jackson County of the Michigan state. It is an elongated ridge of pitted outwash surrounded on both sides by ice-contact slopes known as the ice-channel deposit. This ridge was formed as a result of deposition between ice blocks or collapse of outwash of variable thickness. 11. b. Isolated hills such as the Prospect Hill are promontories or ridges extending a sea or a lake. Glacial features such as the advances of Lake Heron can be seen in the smooth, streamlined surfaces, ground moraines and the recessional end moraine. 11.c. The Prospect Hill and the Cascade Hill both share several glacial features among themselves. Apparently, the deposit of ice from the Lake Heron on the Cascade Hill reached the height of 1250 m. Later, by about 12,000 year BP, the ice retreated from the Prospect Hill after making the first impact. Later, the Rakaia advanced and created a moraine on the western and northern sides of the Prospect Hill. Another unknown lake created wave-cut beaches on the eastern side of the Prospect Hill. Thus, several glacial impacts have played their hand in forming the Prospect Hill. 11. d. High grade sand and gravel. 11. e. It is a commonly observed fact that the regions which are not eroded in a glacial advance often exhibit swampy and lake-like features. This is probably the reason behind the Blue Ridge being swampy. 11. f. 11. g. These glacial features are known as the Kettle Hole lakes. 11. i. When a block of ice is separated from the main glacier due to a glacial retreat or due to the block calving off the glacier snout and tumbling forward, it may become buried in meltwater segments. Eventually, the block melts and leaves a depression behind. If these depressions later become filled with water, they will be known as Kettle Hole Lakes. Crispell Lake and the Lake Ronkonkoma are examples of such lakes. 12. a. i. Erosional feature: Mt. Katahdin in the Baxter state park. Deep semi circular cirques caused by local, alpine glaciers can be seen on the flanks of the mountain. Somes Sound, the fjord on the eastern side is another example. ii. The Granite Ledge in Westbrook, Bubble Rock boulder sitting atop the Bubble Mountain in Acadia National Park. iii. Kezar Five Ponds in Waterford, Bridgton and Bad Mountain, Albany. 12. b. The most recent glacier to have appeared in Maine was the Laurentide Ice sheet which started from Canada about 25,000 years ago and stayed in Maine for over 15,000 years. The direction of ice flow was towards the southern parts of the state. This is evident from the fact that a majority of moraines occur in the southern part of the state. The moraines at the Bouldery moraine ridge in Sedgwick, Tracy corner pit in Addison and the gravel pit of Lyman help in determining the direction of ice flow. 13. a. The thick blue line traces the inland marine limit which is the set of all places where the rise of water at critical junctures was less than the rise of the land. 13. b. They were deposited in the sea. 13. c. Along with the rise in sea level, the glaciers also caused drastic rises and falls in the land. Due to this some of the highest terrains were submerged while others were lifted upwards. 13. d. 14. a. A positive number in the Winter column indicates that the glacier acquired more mass in the winter thanks to process such as precipitation, meltwater freezing etc. 14. b. The ‘Net’ column indicates the sum of mass gained by the glacier during the winter and summer seasons. However, if the loss during summer is greater than the gain in winter, the ‘Net’ becomes negative implying that the glacier lost more mass in this year. 14. c. Year Winter Summer Net Cumulative Balance 1980 1.83 -2.85 -1.02 -1.02 1981 2.28 -3.12 -0.84 -1.86 1982 3.11 -3.03 0.08 -1.78 1983 1.91 -2.68 -0.77 -2.55 1984 2.38 -2.26 0.12 -2.43 1985 2.18 -3.38 -1.20 -3.63 1986 2.45 -3.06 -0.61 -4.24 1987 2.04 -4.10 -2.06 -6.30 1988 2.44 -3.78 -1.34 -7.64 1989 2.43 -3.34 -0.91 -8.55 1990 2.60 -2.71 -0.11 -8.66 1991 3.54 -3.47 0.07 -8.59 1992 1.91 -3.92 -2.01 -10.6 1993 1.98 -3.21 -1.23 -11.83 1994 2.39 -3.99 -1.60 -13.43 1995 2.86 -3.55 -0.69 -14.12 1996 2.94 -2.84 0.10 -14.02 1997 3.71 -3.08 0.63 -13.39 1998 2.76 -4.62 -1.86 -15.25 1999 3.59 -2.57 1.02 -14.23 2000 3.32 -2.94 0.38 -13.85 2001 1.90 -3.47 -1.557 -15.407 2002 4.02 -3.47 0.55 -14.857 2003 2.66 -4.76 -2.1 -16.957 2004 2.08 -3.73 -1.65 -18.607 2005 1.97 -4.42 -2.45 -21.057 14. d. 14. e. 14. f. 14. g. Read More