New insights into rock weathering from high-frequency rock temperature data: an Antarctic study of weathering by thermal stress

A major limitation of many weathering studies has been the acquisition of rock temperature data at insufficiently frequent intervals for the meaningful determination of the rate of change of temperature (ΔT/t). Equipment and/or logistical constraints frequently facilitate temperature measurement at only hourly intervals or, at best, every 10 min. Such data are not adequate for the determination of ΔT/t required for the evaluation of the freeze–thaw mechanism or thermal stress fatigue. Recent undertakings at different sites in Antarctica (and at other cold-region locations) provide rock temperature measurements at 1-min intervals, which indicate that the perception of the weathering regime would be very different from that generally assumed from longer-interval geomorphological data. These data clearly show that thermal stress fatigue and thermal shock may be more active components of the Antarctic weathering regime than have generally been recognised; the aridity of the study area limits the role of freeze–thaw weathering. Values of ΔT/t of ≥2 °C min−1 that suggest thermal stress fatigue/shock is operative were recorded; observations of rock flaking are thought to reflect the impact of thermal stress. Further, the data show that contrary to general perceptions, the southern aspect can, in summer, experience higher rock surface temperatures than the north-facing exposure. An examination of rock fracture patterns found in the field shows great similarity to fracture patterns developed in the laboratory as a direct result of thermal shock. The argument is made that greater cognizance should be given to thermal effects.