ROCK SURFACE ROUGHNESS AS AN INDICATOR OF DEGREE OF ROCK SURFACE WEATHERING

Rock surface weathering often leads to increased rock surface roughness, but roughness has proved difficult to quantify. Several instruments are available for micro-mapping and recording rock surface profiles, but the most appropriate for most purposes is the simple profile gauge. Short profiles can be recorded quickly and accurately. A range of roughness indices has been proposed in other areas of geomorphology and their efficacy as measures of roughness at scales of interest in studies of weathering is assessed. Some are too complex or labour-intensive and others are too sensitive to the scale of roughness to provide reliable measures of magnitude. The most appropriate indicator of both the scale and magnitude of roughness is the standard deviation of the differences between height values at a range of set horizontal intervals along a profile (the ‘deviogram’). Varying the measurement interval records roughness at different scales. A regression approach (root-mean-square roughness) provides a reliable measure of the magnitude of roughness at the maximum scale present. Three case studies confirm the efficacy of these approaches to studies of weathering of different rocks in different environments. Software is supplied which automates the calculation of roughness indices from gauge profiles.

[1]  Weathering phenomena in a cool temperate climate , 1989 .

[2]  David John Unwin,et al.  Introductory Spatial Analysis , 1982 .

[3]  Stig Nordbeck.  Computing distances in road nets , 1964 .

[4]  D. McCarroll.  Differential weathering of feldspar and pyroxene in an arctic‐alpine environment , 1990 .

[5]  D. Pheasant,et al.  Delimitation of Weathering Zones in the Fiord Area of Eastern Baffin Island, Canada , 1974 .

[6]  Bruce N Wilson,et al.  Soil topography measurements using image processing techniques , 1988 .

[7]  R. C. Speck,et al.  APPLICABILITY OF FRACTAL CHARACTERIZATION AND MODELLING TO ROCK JOINT PROFILES , 1992 .

[8]  T. Hawkins.  A Note on Rhythmic Layering in Hornblende-rich Picrite and Dolerite Intrusions, near Rhiw, Caernarvonshire , 1965, Geological Magazine.

[9]  J. Bradford,et al.  Portable laser scanner for measuring soil surface roughness. , 1990 .

[10]  E. Blackwelder.  Pleistocene Glaciation in the Sierra Nevada and Basin Ranges , 1931 .

[11]  J. Y. Wang,et al.  A Laser Microreliefmeter , 1988 .

[12]  D. McCarroll.  The schmidt hammer, weathering and rock surface roughness , 1991 .

[13]  R. Dugdale.  The Quaternary History of the Northern Cumberland Peninsula, Baffin Island, N.W.T. Part III: The Late Glacial Deposits of Sulung and Itidlirn Valleys and Adjacent Parts of the Maktak-Narpaing Trough , 1972 .

[14]  Terry E. Tullis,et al.  Euclidean and fractal models for the description of rock surface roughness , 1991 .

[15]  Joe M. Bradford,et al.  Applications of a Laser Scanner to Quantify Soil Microtopography , 1992 .

[16]  P. Birkeland.  Subdivision of Holocene glacial deposits, Ben Ohau Range, New Zealand, using relative-dating methods , 1982 .

[17]  M. Klein.  A quantitative approach to the analysis of slope roughness and effective slope angle , 1981 .

[18]  R. Sharp.  Semiquantitative Differentiation of Glacial Moraines near Convict Lake, Sierra Nevada, California , 1969, The Journal of Geology.

[19]  Kenneth G. V. Smith,et al.  Standards for grading texture of erosional topography , 1950 .

[20]  A DIGITAL SURFACE-ROUGHNESS METER , 1994 .

[21]  A Technique for the Classification of Hill-Slope Forms , 1978 .

[22]  R. Green,et al.  Statistical Geomorphology of the Lunar Surface , 1970 .

[23]  John N. Rayner,et al.  Introduction to Spectral Analysis , 2005, Spectral Analysis for Univariate Time Series.

[24]  A. Nelson.  CHRONOLOGY OF QUATERNARY LANDFORMS, QIVITU PENINSULA, NORTHERN CUMBERLAND PENINSULA, BAFFIN ISLAND, N.W.T., CANADA , 1980 .

[25]  Dominique Courault,et al.  Testing roughness indices to estimate soil surface roughness changes due to simulated rainfall. , 1990 .

[26]  S. Dahl,et al.  Degree of rock surface weathering as an indicator of ice-sheet thickness along an east-west transect across southern Norway , 1994 .

[27]  T. M. Lillesand,et al.  Remote Sensing and Image Interpretation , 1980 .

[28]  J. F. Nye,et al.  Glacier sliding without cavitation in a linear viscous approximation , 1970, Proceedings of the Royal Society of London. A. Mathematical and Physical Sciences.

[29]  P. Curran.  The semivariogram in remote sensing: An introduction , 1988 .

[30]  David M. Mark,et al.  Geomorphometric Parameters: A Review and Evaluation , 1975 .

[31]  J. Dugundji,et al.  A study of microrelief—its mapping, classification, and quantification by means of a fourier analysis , 1965 .

[32]  Stephen R. Brown,et al.  Broad bandwidth study of the topography of natural rock surfaces , 1985 .

[33]  R. J. Pike,et al.  SPECTRAL ANALYSIS OF LANDFORMS , 1975 .

[34]  N. Odling,et al.  Natural fracture profiles, fractal dimension and joint roughness coefficients , 1994 .

[35]  H.R.G.K. Hack,et al.  Difficulties with using continuous fractal theory for discontinuity surfaces , 1996 .

[36]  R. Shakesby.  The soil erosion bridge: A device for micro‐profiling soil surfaces , 1993 .

[37]  Ali Saleh,et al.  Soil roughness measurement: Chain method , 1993 .