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Weathering of Rocks in Arctic and Sub-Arctic Environment
The rocks found in the sub-Arctic and Arctic environments are subject to extreme range of temperatures, and to frequent freezing and thawing cycles. Frost action was always assumed to be the principal method of weathering of rocks in these regions.
Frost action was likewise considered to be the major force responsible for break-down of rock aggregates and of concrete. As part of a study designed to better understond the rocks’ response to frost action, the following phenomena were observed.
1. Water contained in the most of the “frost” sensitive argillaceous carbonate rocks did not freeze, even under extreme temperatures commonly encountered in the Arctic.
2. Most of this water is in an adsorbed state.
3. The rocks of this type tended to saturate under high humidity conditions alone.
4. The adsorbed water in these rocks is in a rigid state, as shown by increase in shear wave velocity.
5. Upon saturation in air, or in water, these rocks expand, and they exert pressure if confined.
6. “Frost” type weathering of rocks that tend to saturate with adsorbed water can be observed in climates where freezing rarely takes place.
The author proposes, that, in the case of fine-grained sedimentary rocks, the frost phenomenon is of minor importance. The rocks fail due to the expansive action of the rigid, adsorbed, non-freezable water contained in the sorption sensitive rocks. The failure is by fatigue due to expansion and contraction on sorption and desorption, and is enhanced by large temperature fluctuations and cycling in the freezing and thawing range. True frost action is active only in the coarser grained rocks, and only in those that saturate critically by absorption of bulk water.
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