Tasman Glacier Essay

Introduction
Glaciers are flowing rivers of ice that form where there is an accumulation of winter snow that does not melt in the following summer. The Tasman Glacier is a melting and calving glacier located in the Mount Cook National Park at the base of the Southern Alps of New Zealand. During the 1950’s the glacier moved into a state of retreat, which was ultimately caused by the coalescing of supra-glacial pools that formed the Tasman Lake (Kirkbride, 1993). The lake then allowed new processes to occur which have rapidly increased the rate at which the retreating is occurring. The aim of this report is to investigate the changes occurring in the ablation zone of the Tasman Glacier and the processes that bring about those modifications. These changes would be expected to follow a negative trend as the Tasman Glacier (like other New Zealand glaciers) is in a current state of retreat due to global temperature rise and local processes. The aim will be achieved by studying the area through the use of aerial photos, stereoscopic analysis and comparison of ASTER images used to show the change to the landforms of the area over a period of time (2000- 2012). This investigation is important as it demonstrates the effects that interacting natural processes can have on an environment, which can be used to predict future patterns.

Methods
There were three methods used in the undertaken experiment. A geomorphic map was produced through the process of tracing over the image 27114. Glacial features were then sketched onto the map with reference to image 27114. To assist in the construction of the geomorphic map, a stereoscope was used to give a three dimensional representation of the Tasman Valley and surrounding areas. This provided a more enhanced view of the subject area, which helped develop a better understanding of the scale of the processes occurring. Finally, a comparison of the ASTER images (2000-2012) was undertaken which displayed a clear change in the shape of the Tasman Lake landform.

Results
Through analyzing the constructed geomorphic map and viewing the images through the stereoscope, a number of landform features were identified that displayed the natural processes operating in the area. The Tasman Glacier is the main agent responsible for the creation of landforms and large-scale changes in the area. The most obvious landform created through these interacting natural processes is the Tasman Lake. The lake is situated at the terminus of the glacier and is dammed by the recessional moraine mounds that were deposited during the glaciers last stage of advance. The dynamic nature of this particular landform and the change of the Tasman glacier were clearly evident through the comparison of the ASTER images (2000-2012) and the 1976 and 1986 aerial photos. In the 1976 aerial photograph, the lake was non-existent but its early stages were evident through the supra-glacial pool formation on the surface. The 1986 aerial photograph displayed larger pools that suggest the small initial pools coalesced. The comparison of the aerial photographs and ASTER images showed how the Tasman Lake accelerated the recession of the glacier due to the contact at the terminal face. This also outlined the relationship between the two landforms. As the glacier retreated up the valley, the lake grew larger and occupied the space the retreating glacier created. However, the glacial melt water is not the only source of in water budget to the lake evident from the observations. The glacial fed Murchison River is a braided river that is located to the eastern side of the Tasman Glacier and has an entry point at the southern end of the lake. These are the two main inflow sources of water into the lake. However the Tasman River, an outwash stream that flows from the southern end of the Tasman Lake and is the main out water budget for the lake, balances these inflows. Another landform that is evidence of glacial action is the large lateral moraine walls

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