Comment on "Lightning as a geomorphic agent on mountain summits : evidence from southern Africa" by Knight and Grab (2014)

Show simple item record Sumner, P.D. (Paul) 2014-05-12T06:17:20Z 2014-05-12T06:17:20Z 2014-04
dc.description.abstract Insights into the possible effect of lightning strikes on rock breakdown are presented by Knight and Grab (2014) froma summit area in the Lesotho highlands. Based on their findings, the authors challenge the association of angular debris with frost shattering and use this as a platform for directing critique against palaeo-geomorphic studies.While the lightning strike data are not questioned directly here, the palaeo-environmental contextwithin which the paper is set, the portrayal of former findings and the assumptions regarding weathering mechanisms in Lesotho are commented on. Frost shattering is the centre of Knight and Grab's weathering critique but, contrary to that stated in their text, none of the cited authors invoke this process in Lesotho. Other weathering processes that are speculated upon are not specific to cold climates either and thus cannot be used in support of their argument. In terms of debris and block distribution, lightning will not account for the preferential location of relict blocks and debris below the summits on south-facing slopes, or for the extensive valley floor accumulations that are documented in Lesotho. Knight and Grab also falsely portray former studies by implying that palaeo-environmental inferences in the area are drawn fromblock origin or morphology alonewhen the climatic signatures were derived from integrated assessments. In a palaeo-context, the relative contribution of lightning to debris production under dryer and colder conditions, when convective thunderstorm activity in the highlands was likely reduced, is also questioned. The weathering context, as well as the critique that Knight and Grab direct at other studies on relict landforms, is thus shown as inappropriate. en_US
dc.description.librarian hb2014 en_US
dc.description.uri en_US
dc.identifier.citation Sumner, PD 2014 , 'Comment on "Lightning as a geomorphic agent on mountain summits : evidence from southern Africa" by Knight and Grab (2014)', Geomorphology, vol. 211, pp. 134-136. en_US
dc.identifier.issn 0169-555X (print)
dc.identifier.issn 1872-695X (online)
dc.identifier.other 10.1016/j.geomorph.2013.12.011
dc.language.iso en en_US
dc.publisher Elsevier en_US
dc.rights © 2014 Elsevier B.V. All rights reserved. Notice : this is the author’s version of a work that was accepted for publication in Geomorphology. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Geomorphology, vol.211, pp. 134-136, 2014. doi : 10.1016/j.geomorph.2013.12.011 en_US
dc.subject Lesotho en_US
dc.subject Lightning strikes en_US
dc.subject Frost shattering en_US
dc.subject Debris production en_US
dc.subject Periglacial processes en_US
dc.subject Openwork block accumulations en_US
dc.title Comment on "Lightning as a geomorphic agent on mountain summits : evidence from southern Africa" by Knight and Grab (2014) en_US
dc.type Postprint Article en_US

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