Introduction: Landscape Assemblages and Transitions in Cold Regions

Abstract

This essay introduces the varieties and distinctive characteristics of cold regions. A landscape approach is adopted, emphasising associations of land forms and sediments and the importance of spatial and temporal transitions in earth surface processes. The broadest classes of cold region are the ``zonal{''} or higher latitude examples, and the ``azonal{''} ones based on elevation, continentality and air mass regimes. Vast and singular subregions are also characterised by cold tolerant ecosystems such as heathlands and bogs, boreal or montane forests. These play a major role in landform development and appearance in their respective zones. Work relating to earth surface processes tends to separate glacierised (i.e., icecovered) and non-glacierised areas, in the latter, periglacial and nival regimes, and cold coastal conditions. Cold regions geomorphology, in recent decades, has focused on processes peculiar to low temperatures and freeze-thaw. Much of our understanding has developed out of specialised investigations and experimental work on distinctive processes of these regimes, and the search for more abstract, general models of them. But a regional and comparative perspective must also recognise the large role played by weathering, fluvial, lacustrine, marine or aeolian processes shared with other regions if modified in cold contexts. A landscape and comparative interest directs attention to the variety of landform associations and related sediment assemblages, and how they represent the complexities of on-going and historical development. Most cold regions landscapes record past and on-going environmental change. They contain more or less extensive legacies of clima-hydrological, ecological and geotectonic changes in the Quaternary. They involve glaciation and deglaciation, isostatic crustal adjustments, fluctuations in sea levels and in the extent of marine and freshwater ice, changes in snow covers, seasonal ground ice, and the patterns and thickness of permafrost. These legacies, and how they are removed or transformed, are integral to the interpretation of existing cold region landscapes. What we observe are geomorphic ``palimsests{''} in which relict, overlapping and replacement forms are interwoven. The notion of ``transition{''} addresses the sense in which landscape development is not merely chronological and linear, or simply a ``lagged{''} response to climatic and tectonic changes. There are diachronous episodes of (incomplete) readjustment to the cessation of past conditions, and towards later conditions, of which those at present are only one set. There are distinctive spatial and temporal patterns of adjustment, including 14 self-adjustment{''} specific to the earth surface processes at work. The paraglacial is a classic example. It is suggested that such temporal and spatial responses in earth surface processes apply much more generally as part of landscape transformation in the Quaternary.