Long-term landform evolution: Evidence from talus studies

Abstract

Current concepts of long-term landform change like equilibrium, characteristic forms or the role of climate were developed with the denudational history of landscapes in mind. In this paper some long-term aspects of talus development are discussed as an example of the potential contribution from dominantly depositional environments to the more theoretical concepts of geomorphology. Evolutions during periods of 102 to 103 years as well as during longer periods (in the order of 104 to 105 years) are mentioned. Interpretations of geomorphological evolution for the latter time scale and within a regional context may be obtained from the information contained within the shorter time slices studied in detail on individual taluses. Periods for which the evolution of part of a talus is known in detail, in terms of process types and sequences in relation to climate and other environmental factors, are indicated here as time slices. It is suggested that the combination of such time slices for a given region may result in a more or less complete picture of geomorphological and environmental evolution for relatively long periods. The image obtained is additional to information from other reconstructions of environmental conditions. Two examples of talus research are discussed to explain the intentions of the paper. Concluding statements draw attention to the potentially strong relationships between properties of talus deposits and environmental conditions. This is especially important for information that cannot be obtained from other sources like pollen analysis, for instance about precipitation characteristics. At a more general level of geomorphology, a possible modification of ideas is proposed about the influence of climate on the functioning of certain geomorphology systems. Further consequences of the results are the need to re-think concepts like equilibrium or characteristic form. © 2002 John Wiley and Sons, Ltd.