Colin E. Thorn (editor) - Space and Time in Geomorphology: Binghamton Geomorphology Symposium 12

Volume 27

Edited by
COLIN E. THORN

First published in 1982 by George Allen & Unwin Ltd

This edition first published in 2020

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1982 Colin E. Thorn

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ISBN: 978-0-429-29797-7 (Volume 27) (ebk)

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Edited by Colin E. Thorn

Department of Geography, University of Illinois at Urbana-Champaign

London
GEORGE ALLEN & UNWIN
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Copyright 1982 by Colin E. Thorn

First published in 1982

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LIBRARY OF CONGRESS CATALOGING IN PUBLICATION DATA SPACE AND TIME IN GEOMORPHOLOGY

Bibliography: P.

Includes Index.

1. GeomorphologyCongresses.

I. Thorn, Colin E.

GB400.2.S67 551.4 81.21740

ISBN 0-04-551056-3 AACR2

BRITISH LIBRARY CATALOGUING IN PUBLICATION DATA

Space and time in geomorphology.(The Binghamton symposia in geomorphology; no. 12)

1. Geomorphology-Congresses

I. Thorn, Colin E. II. Series

551.4 GB400.2

ISBN 0-04-551056-3

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Uniformitarianism and the ergodic hypothesis are fundamental concepts in contemporary geomorphology. In the case of uniformitarianism there has been a protracted debate over the true usefulness of the term (e.g. Gould 1965). In truth, the worst that can be said about it is that it is cacophonous and anachronistic. However, the ergodic hypothesis has rarely been put to the test (Savigear 1952 is one of a few classic exceptions), although in a generalized form it is inextricably woven into the fabric of contemporary geomorphology.

As geomorphic theory has developed, both uniformitarianism and the ergodic hypothesis have been recast. Magnitude and frequency (Wolman & Miller 1960) updated simplistic uniformitarianism, only to be modified itself by the notions of healing time (Wolman & Gerson 1978), episodic erosion (Schumm 1977) and the entire range of threshold-related concepts (Coates & Vitek 1980). Church and Mark (1980) have seriously questioned ergodic principles (space time substitution) in their comparison of static and dynamic allometry. Indeed, Church (1980) has gone right to the heart of the matter by suggesting that process geomorphology provides little or no insight into landscape evolution. Such a perspective appears readily defensible and places even greater onus on stratigraphic interpretation for studies of landscape evolution. Unfortunately, the weak linkage between the alluvial record and interfluvial geomorphology (Costa 1975, Caine 1974), plus an insightful reappraisal of the stratigraphic record itself (Ager 1973) suggest an equally pressing need for careful reconsideration of traditional concepts on these fronts as well.

Clearly, geomorphology stands at something of a Rubicon. Faced with a dearth of data, it is essential to press forward on another front, namely, that of establishing a more cogent and comprehensive paradigm. There is certainly nothing new in this notion, as it has been stated eloquently by Davis (1899) and Chorley (1962). A meaningful grasp of landscape evolution would seem to depend upon: (a) understanding the present spatial distribution of processes and process rates, especially the linkage between erosional and depositional components; (b) comparison of spatial versus temporal change; and (c) careful appraisal of the character and composition of the stratigraphic record. The size of the task is herculean, but one obvious starting point is a theoretical examination of the characterisitics of available data sets for the specific purpose of shaping future field measurement studies more purposefully.

This symposium was conceived with many of the above points in mind. It was inspired by the success and significance of the ninth Binghamton symposium on thresholds in geomorphology (Coates & Vitek 1980) and was consciously designed to complement the initial focus on across-threshold variability with one upon between-threshold variability. Each participant was invited to use a data set to address between threshold variability in either a spatial or temporal context or, if possible, both.

The paper by Derek C. Ford and John J. Drake makes a singularly appropriate introduction because in it they suggest that karst erosion has no intrinsic thresholds and therefore the entire span of Holocene time constitutes a meta-stable karst erosion phase. Integration of a variety of measurement techniques permits variations in limestone erosion and speleothem deposition to be examined over a range of timescales. However, temporal variability can be successfully evaluated only in association with a sound grasp of spatial variability.

Equilibrium concepts are central to geomorphology, and John B. Thornes sets out to examine both the behavior and stability of equilibria. He is able to demonstrate that autocorrelative properties permit recognition of basic process structures in temporal series, even when a large portion of the data sequence is missing. Estimation of spatial and temporal variability using the normal generated distribution (ngd) is developed and demonstrated by H. Charles Romesburg and Jerome V. DeGraff. The ngd is particularly flexible and its estimation is simpler than that of the beta-binomial distribution. The ergodic hypothesis is tested mathematically by Richard G. Craig, using data from the Appalachian Mountains of Pennsylvania. In addition to tending to confirm the ergodic principle, the model suggests that stable landforms cannot occur, but that there is an oscillating effect about a preferred value.