Preliminary results from experimental weathering studies

Abstract

Freeze‑thaw and wetting‑drying experiments with about 90 different Swedish rocks are described. The amount of debris formed from Pre­cambrian rocks after 432 freeze‑thaw cycles is very low. In some cases it is less than 0.001 % of the original weight. In spite of the low weathering rate it has been possible to establish a scale of how susceptible different rock types are to this type of weathering. On an average sandstones decomposes 11 times faster than granites. The soft sedimentary rocks included in the experiment have produced between 1 100 and 31 000 times more material of grain sizes less than 1 min than the mean for granites. The observed weath­ering rate from the freeze‑thaw cycles is about 100 times slower than the rate calculated by measuring the height of quartz veins above the surrounding rock in the field. The amount of material produced after 396 wetting‑drying cycles is generally an order of magnitude lower than in the freeze‑thaw experiment. For two of the limestones it is more than 500 times lower.