Rock Temperatures and Implications for Cold Region Weathering. I: New Data from Viking Valley, Alexander Island, Antarctica

Abstract

A principal tenet of cold region weathering studies is that of temperature. Unfortunately, despite the appearance to the contrary, actual data are still sadly lacking in many instances. Here data are provided for the best part of two Antarctic winters plus, at two minute resolution, for one summer, from a variety of positions within a dry valley. The data clearly show the dangers of using air temperature as a surrogate for thermal conditions either at the rock surface or at depth in the rock. Although detailed rock moisture data are absent in this study, indirect evidence from both observation and non‐destructive ultrasonic testing shows that water is extremely limited during the period of freeze–thaw cycles. Thus, despite the occurrence of the thermal events no damage can result from frost action. Detailed data at two minute intervals show the importance of such high resolution observations. It is argued that without data acquisition at two minute or preferably one minute intervals, it is not possible to discern the weathering regime, including interpreting the freeze–thaw process. These data show that processes such as thermal stress fatigue/shock are possible and that rates of change of temperature ≥ 2°C min−1, as required for thermal shock, do occur. Measurements of taffoni size and occurrence, coupled with Schmidt hammer rebound values, show that the eastern aspect experiences the least weathering whilst the northern and western exposures have the greatest amount. This observation is in accord with separate findings of aspect‐controlled orientation of “cryoplanation” terraces at higher elevations. Some speculative suggestions for the cause of this aspect‐controlled weathering are given, the most important of which is that it is unlikely that freeze–thaw plays any significant role—a factor that underscores its qualitative presumption in cold regions and questions the origin and development of cryoplanation forms. Beyond anything else, this paper indicates the complexity of rock temperature regimes and suggests that it is the synergistic relationships between different weathering processes that are important. © 1997 John Wiley & Sons, Ltd.

Honeycomb development on Alexander Island, glacial history of George VI Sound and palaeoclimatic implications (Two Step Cliffs/Mars Oasis, W Antarctica)

“…As already suggested by Hall (1997) and Meiklejohn and Hall (1997) based on Horne (1967Horne ( , 1968 and Taylor et al (1979), the gypsum source is most probably the local bedrock that comprises calcite cement and veins. Pyrite nodules that are abundant in Alexander sandstones (Thomson, 1964) are a possible source of sulfates, together with snow that contains sulfates supplied by the atmosphere (see review in: Ishimaru and Yoshikawa, 2000, pp.…”

“…Note the silt enrichment at the base of the tafoni infill due to silt translocation by snowmelt waters. Hall, 1997). These authors suggest that the abundance of gypsum in the study area can be at least partly inherited from a deglaciation phase that generated abundant meltwaters.…”

“…For instance, an early reconstruction of glacial advances and retreats in the eastern part of Alexander Island was provided by Clapperton and Sugden (1982). In the same area, present-day rock weathering processes are being investigated and monitored (e.g., Hall, 1997;Meiklejohn and Hall, 1997;André, 2001, 2003), but to date, alveolar weathering phenomena have not been studied in a historical perspective in the Peninsula.…”

Soil characteristics on varying lithological substrates in the South Shetland Islands, maritime Antarctica

“…According to Hall (1997) moisture is the main limitation on freeze-thaw weathering. In the peninsulas continuous permafrost occurs above 30 m a.s.l.…”

Geochemistry of soils of King George Island, South Shetland Islands, West Antarctica: Implications for pedogenesis in cold polar regions

“…Soils in this part of the Antarctica are characterized by much greater predominance of cryoturbic processes as evidenced by the presence of patterned ground (Campbell and Claridge, 1987). Recently, it was reported that the main limitation on freeze-thaw weathering is not thermal but rather moisture (Hall, 1997), and that in ice-free areas close to the coastal regions soil formation and chemical weathering occurs to a greater extent than previously thought (Blume et al, 1997;Beyer et al, 2000). In addition, although the reactions are probably slow in Antarctic conditions, chemical weathering was suggested as the main process contributing magnesium, calcium and carbonate ions into the salt deposits (Keys and Williams, 1981).…”