Sinkhole Form as an Indicator of Process in Karst Landscape Evolution
Hansel, Ardith K.
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Permalink
https://hdl.handle.net/2142/67500
Description
Title
Sinkhole Form as an Indicator of Process in Karst Landscape Evolution
Author(s)
Hansel, Ardith K.
Issue Date
1980
Department of Study
Geography
Discipline
Geography
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Physical Geography
Language
eng
Abstract
Although exhaustive studies of solution rate variability have traditionally dominated karst geomorphology they have, so far, failed to identify reliable form-process relationships. This study creates a methodology for precise definition of the morphology of the basic karst unit, the sinkhole; and then using a random, stratified sampling design, postulates and evaluates the importance of non-solutional processes in the development of sinkholes in two contrasting karst subtypes (normal and exhuming fluviokarst) of the Mitchell Plain, south central Indiana.
Sinkhole cross-sections were surveyed in the field using breaks in slope as sample points. A multiquadratic equation was fitted to these sample data to interpolate height values between points and derive slope and curvature distributions for each sinkhole cross-section. Five diagnostic elements (morphometric parameters) were extracted from each profile curve, namely the means of the slope distributions of the two wall segments and the means of the curvature distributions of the two wall segments, plus the base segment. In this manner the cross-sectional shapes of thirty-one sinkholes from the normal fluviokarst and thirty-one sinkholes from the exhuming fluviokarst were characterized.
A conceptual model of the interaction between rates of subterranean sediment removal and alluvial sediment delivery was used to detail hypothetical cross-sectional forms. Normal and exhuming fluviokarst subtypes offer appropriate test cases for the model because normal fluviokarst sinkholes are dominated by efficient alluvial delivery processes and should exhibit saucer-like forms while exhuming fluviokarst sinkholes are dominated by subterranean removal processes and should exhibit funnel-like forms reflecting active sediment removal from the base.
The model was formally tested by using multivariate grouping techniques to develop a valid morphologic classification of the sixty-two sinkhole forms. Four distinct sinkhole form types were identified. Statistically significant differences in the frequency of occurrence of the four sinkhole form types between the normal and exhuming fluviokarsts were ascertained at the 99.9% level. The normal fluviokarst was dominated by saucer-shaped forms while in the exhuming fluviokarst the funnel-shaped form was most common. These frequency distributions of the form types were consistent with those predicted by the hypothetical models.
It is concluded that a morphogenetic approach to landscape karstification is appropriate. The form measures used herein have widespread applicability not only in karst geomorphology but in other subfields of geomorphology as well. Additionally, the study has been successful in highlighting the significance of non-solutional processes in the variability of the surface morphology of karst landscapes.
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