| Abstract: | Recently it has been proposed that stress generated by the adsorption of water to clay surfaces in argillaceous rocks may be an important agent of mechanical weathering in polar and alpine environments, implying that long-held views on the status of frost action in these areas may be in need of revision. This study documents the response, under controlled experimental conditions, of aggregates of fresh and partlyweathered schist and fresh pre-cut schist blocks to 500 accelerated (12 hour) freeze-thaw and hydration-dehydration cycles. Aggregate samples subjected to freezing cycles produced the largest amounts of material in the less than 2 mm size range (an average of 8 per cent and 16 per cent for the fresh and partly-weathered aggregates respectively), whereas humidity cycles above and below freezing yielded lesser amounts (3 per cent and 4 per cent respectively). The fresh schist blocks were found to be highly resistant to both mechanisms; only those experiencing freeze-thaw oscillations produced measurable amounts of detritus. Although hydration effects were not as effective as frost action in causing particle size reduction in aggregates, the two mechanisms may well reinforce one another in periglacial environments, enhancing the ability of these areas to serve as source regions for loess. |
