Rock temperatures and implications for cold region weathering. I: New data from Viking Valley, Alexander Island, Antarctica
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.