The impact of solar radiation upon rock weathering at low temperature: a laboratory study

The impact of solar radiation heating upon rock temperatures in a cold environment was investigated by an experimental simulation. Different rock samples, collected from the central part of the Tibet Plateau, were pre-treated and put in a low-temperature box. Temperatures in the box changed by a radiation heat source that simulated solar insolation. Results show that the temperature-increase rate of samples saturated by water is similar to that saturated by salt solution, but the decrease rate of the former is higher than the latter. The temperature rebound derived from the potential heat release of the rock-interstitial water transition at -4 degreesC occurred more frequently on samples saturated by water than upon those saturated by salt solution. Salt content is a possible agent that inhibits the freeze-thaw process. Insolation heating induces faster temperature variations on the rock surface than in the interior. This is more closely related to rock mineral composition than to pore size and pore density. This implies that fast temperature variations may lead to the continuous expanding and contraction of the rock minerals. This may result in rock fatigue and may dominate the weathering process. These results, applied to different rocks saturated by water or salt solution, are also supported by measuring changes in ultrasonic-wave-transmitting rates. Copyright (C) 2003 John Wiley Sons, Ltd