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Breccia
The term breccia is used to describe deposits which can be
hugely variable. Basically they consist of limestone and other
rock fragments broken from the walls and roof of the cave
and sometimes outside, mixed with sand and sometimes cemented
with flowstone. Breccia builds up as a result of alternating
freezing and thawing. During the winter and periods of increased
cold, water freezes in rock crevices causing pieces of limestone
to break away from the cave wall or roof. During warmer weather,
water, which flows through the cave and between the limestone
fragments washes in sand, silt and clay. Subsequent formation
of flowstone can cement these pieces of limestone and the
sediment between them into a solid mass. The early excavators
at Creswell Crags tell us how they used explosives to remove
the breccia from Robin Hood Cave.
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