Geology Reference
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Figure 3.2.
(a) Flaking of granite around corestones at Palmer, eastern Mt Lofty Ranges, South Australia.
(b) Spalling in granodiorite in the Snowy Mountains, New South Wales.
whereas their shady undersides, and especially any parts covered by desert sand or river silt - both
of which hold moisture, in the case of the desert sand most commonly derived from dew or fog -
show clear signs of alteration. Such observations do not preclude disintegration due to insolation,
but they strongly suggest that chemical changes due to contact with water act more rapidly. Also,
in Galicia, there are rock carvings 5,000-7,000 years old. Some of them were buried by soil.
Others were not. Those which were covered are more decayed than those that remained exposed,
because the soil held moisture which attacked the rock surface.
On the other hand, temperature oscillations in the presence of moisture apparently cause frag-
mention, both above freezing, and around freezing point (Grawe, 1916). Well-fractured rocks are
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