Lecture
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Lecture
15
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| Geomorphological mapping - history, methods, contemporary applications. From NASA |
The study of landforms is still the essence of Physical Geography. The ability to recognise and explain the production of landscape facets is essential to the understanding of landscape development. Variety in scale and form provide the challenge for geomorphologists studying landforms, explanation of variation is the key to unlocking the history of environmental change. The lecture will demonstrate the variety of evidence that can be investigated, and some of the techniques of investigation, through analysis of the following themes:
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| Remote Sensing and Glacial Landforms - from NASA | |
| Mapping and Permafrost - PACE | |
| bbc radio link for workshop | |
Mapping is the essential tool of the geomorphologist. mapping techniques have become more important with time as changing technology allows more complex mapping. There are a variety of maps that can be produced, topographic, land use, land type (soil, vegetation), but the most important is the geomorphological map.
Geomorphological maps contain information on the morphology, genesis and age of landforms. They mark the presence of key features in the landscape, and depict certain attributes. Geomorphological maps are therefore more ‘interpretative’ (Lowe & Walker, 1998) than other kinds of map, which is a fancy way of saying that they are 'subjective' (Harris:this publication) or perhaps even a work of fiction, if I may be so cynical.
The production of geomorphological maps starts with aerial photography and ground survey: photography (including satellite imagery) can enable the production of a base map which is then 'ground truthed' in the field. ground truthing is an important part of the process: small scale features can often be missed, and larger scale features can be misinterpreted. The accuracy and speed of mapping is continuously being improved by more the availability of more sophisticated equipment, in particular GPS is a new and potentially powerful ally, but remote sensing will always be the basic foundation. As the world thaws out from the cold war ever more sophisticated data is becoming available, in particular Radar and GPR extend mapping capabilities. All those spy satellites need to be put to some use!
Glacial landforms, especially 'fresh' landforms can be utilised to create quite detailed reconstructions of former environments. The location of ice contact slopes, trimlines and moraines can enable reconstruction of former glacier profiles. Studies of contemporary glaciers, particularly the mass balance of temperate glaciers, can enable reconstruction of flow rates and estimates of debris throughput and rates of erosion. Direction of movement and also rates of movement can be suggested by the study of streamlined landforms such as drumlins, flutes and whaleback forms as well as smaller scale landforms such as crescentic gouges and striae.
Relict periglacial landforms have been studied in order to reconstruct former climatic environments. Frost wedging and polygon formation are known to occur under certain climatic conditions, whilst other processes and landforms are associated with the presence of permafrost. It should be noted that not all 'periglacial' processes are unique to periglacial environments, tors for example can form under a number of different climatic regimes and the origin of certain kinds of landform is disputed, such as altiplanation terraces.
Fluvial landforms can give clues as to former rates and regimes of fluvial environments. landforms such as deltas can help trace former lake shorelines and sea levels. A river terrace can prove to be a very useful spatially extensive datum, important for the correlation of events. Coastal landforms can provide evidence similar to fluvial landforms for environmental change, although the most obvious interpretations are related to sea-level change.
Although not necessarily unique to the low latitudes, the analysis of lake levels (and/or palaeolakes) and dune fields (palaeodunes) have enable reconstructions of environmental change away from those areas characterised by changes associated with glaciation. Such studies have revealed that the earth has typically been much more arid and subject to much stronger atmospheric circulation during the Pleistocene than is presently the case. Changes in the rates and nature of weathering regimes in low latitudes is also revealed by the study of duricrusts such as laterite,calcrete and ferricrete.
The lecture will consider two specific case study examples, one being an undergraduate study, the other being a larger scale project.
Scottish Late Glacial: Bennett, 1994; Bennett & Boulton 1993 a&b; Bennett et. al. 1998.
River Terraces of the Biddulph Valley: Bromley, 1998.
Bennett, M.R. 1994. 'Morphological evidence as a guide to deglaciation following the Loch Lomond Re-Advance: A review of research approaches and models.' Scottish Geographical Magazine, 110, pp. 24 - 32.
Bennett, M.R. & Boulton, G.S. 1993(a). 'A reinterpretation of Scottish "hummocky moraine" and its significance for the deglaciation of the Scottish Highlands during the Younger Dryas or Loch Lomond Stadial.' Geological Magazine, 130, pp 301-318.
Bennett, M.R. & Boulton, G.S. 1993 (b) 'The deglaciation of the Younger Dryas or Loch Lomond Stadial ice-field in the Northern Highlands, Scotland.' Journal of Quaternary Science, 8, pp. 133-145
Bennett, M.R. et.al 1998. ‘Glacial Thrusting and Moraine Mound Formation in Svalbard and Britain: the example of Coire a’ Cheud - chnoic (valley of 100 hills), Torridon, Scotland’. IN: Owen, L.A. (ed) Mountain Glaciation. Quaternary Proceedings No.6, Wiley & Sons, Chichester.
Bromley, C. 1998. An investigation of the river terraces of the Biddulph Valley. Unpublished undergraduate dissertation, Staffordshire University.
Lowe, J.J. and Walker, M.J.C. 1998 (2nd edn.) Reconstructing Quaternary Environments. Longman, Harlow.
Slaymaker, O. and Spencer, T. 1998. Physical Geography and Global Environmental Change. Routledge, London.