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 r ock temperature data at insufficiently frequent intervals for the meaningfu l determination of the rate of change of temperature (DeltaT/t). Equipment and/or logistical constraints frequently facilitate temperature measurement at only hourly intervals or, at best, every 10 min. Such data are not adeq uate for the determination of DeltaT/t required for the evaluation of the f reeze-thaw mechanism or thermal stress fatigue. Recent undertakings at diff erent sites in Antarctica (and at other cold-region locations) provide rock temperature measurements at 1-min intervals, which indicate that the perce ption 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 component s of the Antarctic weathering regime than have generally been recognised; t he aridity of the study area limits the role of freeze-thaw weathering. Val ues of DeltaT/t of greater than or equal to 2 degreesC min(-1) that suggest thermal stress fatigue/shock is operative were recorded; observations of r ock flaking are thought to reflect the impact of thermal stress. Further, t he data show that contrary to general perceptions, the southern aspect can, in summer, experience higher rock surface temperatures than the north-faci ng exposure. An examination of rock fracture patterns found in the field sh ows great similarity to fracture patterns developed in the laboratory as a direct result of thermal shock. The argument is made that greater cognizanc e should be given to thermal effects. (C) 2001 Elsevier Science B.V. All ri ghts reserved.