WEATHERING IN COLD ENVIRONMENTS

Co-worker: Dr Frank Nicholson (Liverpool John Moores University). This research (Hoffelsjokull) was partly funded by the Manchester Geographical Society.

Abstract submitted for British Society for Geomorphology Annual Conference, Durham, September 2009

Research is currently under way to investigate frost weathering processes and resulting morphology on the southern edge of the Hardangervidda plateau in southern Norway (see link to Summer 2004 Norway Expedition). Features observed during a reconnaissance visit in 2002 included relic and active ploughing blocks, patterned ground and frost shattering. This research will be conducted in parallel with work funded by Nuffield Foundation (click on Rock Weathering in the menu on the left hand side for further details).

A range of weathering indices were used to refine existing interpretations of the recession of Falljokull on the southern edge of the Vatnajokull ice cap. Recession of this glacier has left a suite of lateral moraines which are strewn with basaltic and doleritic boulders. Many of these exhibit penetrative weathering features including rinds, and lichens have also colonised many. Techniques included Schmidt hammer rebound, rock strength, lichenometry, weathering rind thickness, clast shape and surface pitting. These were recorded at strategic locations on the crest of each moraine ridge and also along the length of ridges in order to detect any variation in the long profile.

The broad is of this research was to investigate rates and processes of rock weathering in an ice-marginal environment in south-east Iceland. Retreat of the little-known Hoffelsjokull glacier, south-east Iceland, can be dated and mapped on the basis of air photograph interpretation. Recent topographic surveys (Liverpool John Moores University research expedition 2000) have added data on the current position of the glacier along its northern edge. An ice-marginal basalt dyke situated on the north side of the glacier offers a unique opportunity to study relatively short-term weathering rates in a glaciated environment. The dyke which runs from the ice edge up to the 1890 moraine, presents a linear feature in a single lithology located almost perpendicular to dated retreat positions of the glacier. Preliminary observations from a reconnaissance visit in 1999 revealed evidence of a progressive upslope increase in surface weathering.

Field investigations included the following:

1. Rock surface micro-roughness using a micro-toughness meter and profile gauges.
2. Degree of weakening of rock fabric using an 'N' type Schmidt hammer.
3. Characteristics (eg density, aperture and depth) of discontinuities (eg fractures, joints and glacial striations).
4. Weathering rind thickness, mineralogy and magnetic susceptibility.
5. Lichen (Rhizocarpon geographicum) size and population characteristics (to provide a further control on dating).

This research will enable rates and processes of weathering to be determined on a known dated surface. The nature of rock weathering may have implications for interpretation of glacier movement processes. Analysis may help to improve understanding of rock breakdown in cold environments and will provide a new set of weathering rates for comparison with other areas of the Vatnajokull ice cap. The research will also provide a comparative test of the usefulness of different weathering indices for relative age-dating of glacial landforms.

Nicholson, D. T. and Nicholson, F. H. (in preparation). Recent ploughing boulder activity at low elevation in the English Lake District. North West Geography.

Nicholson, D. T. 2009. Holocene microweathering rates and processes on ice-eroded bedrock, Røldal area, Hardangervidda, Norway. In: J. Knight and S. Harrison (eds). Periglacial and Paraglacial Processes and Environments. Geological Society Special Publication 320, 29-49.

Nicholson, D. T. 2008. Rock control on microweathering of bedrock surfaces in a periglacial environment. Geomorphology 101(4), 655-665.

Nicholson, D. T., Nicholson, F. H. and Webber, E. 2004. Micro-weathering processes, rates and morphology: Evidence from a high mountain plateau. Poster presented at the Binghamton Geomorphology Symposium, Kentucky, October 1-3 2004. Abstract.

Nicholson, D. T., Nicholson, F. H., Booth, F. and Wildman, J. J. 2004. Post-glacial weathering and blockstream development in a periglacial environment, Hardangervidda, southern Norway. Poster presented at the Binghamton Geomorphology Symposium, Kentucky, October 1-3 2004. Abstract.

Nicholson D. T. 2002. Quantification of rock breakdown for experimental weathering studies. In: R. Prikryl and H. Viles (eds) Understanding and Managing Stone Decay, Karolinum Press, Prague, 59-74. Abstract.

Nicholson D. T. and Nicholson F. H. 2000. Physical deterioration of sedimentary rocks subjected to experimental freeze-thaw weathering. Earth Surface Processes and Landforms 25, 1295-1307. Abstract.