Weathering - Landforms and Geology of Granite Terrains - page 61

shattering acts rapidly and is very effective in cool latitudes and altitudes, and biota are destroying
carbonate and other rocks at measurable rates in coastal zones in the Mediterranean and in the tropics.
Time is also germane to the problem of weathering, for given long exposure, even slow-acting
processes and reactions assume importance. As many granites are emplaced in the ancient shield lands
or in old orogens, this is a factor of some significance in the granite context. Moreover, as tectonic, cli-
matic and topographic conditions have changed, so may biota and groundwater circulation, for exam-
ple, have changed in time.
Thus, several factors impact on the rate and type of weathering active in given areas at particular
times. Some workers (Birkeland, 1974) emphasise rock composition, others climate, but because
of the importance of water, and the chemicals and biota it carries, in rock weathering, many point to
fracture density as the most important single control of weathering. The salient point, however, is
that most granites are inherently susceptible to moisture attack and are readily weathered and eroded.
Weathering processes in the granite context are further discussed in relation to various specific
landforms in the following chapters.
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