Bulletin of the National Speleological Society - ISSN 0146-9517
Volume 23 Part 2: 39-58 - July 1961
A publication of the National Speleological Society
A Stream Piracy Theory
of Cave Formation
Herbert P. Woodward
This theory attributes all caves to the sudden rearrangement of a specific drainage system, either by the piracy of a higher-lvel system by a lower-level system, or by the capture of surface drainage by underground circulation. Its distinctive feature is its association of the cave-forming process with the histroy of the adjacent surface drainage system, and that it regards a cave as a transitory or impermanent feature of stream development in the same category as a waterfall, a lake, or a river gorge.
The theory postualtes a single stage (not cycle) of cave development although there must have been a necessary pre-cave epoch in which the bedrock acquired an incipient structural porosity along joints and fractures. The trigger which initiates cave development is the activation of swift flow at the water-table level, a situation which is normally absent and is likely to be brought about only by some relatively sudden event. Such causative events might be the fall of sealevel; glaciation and ice melting; a major climatic change; acceleration or relocation of surface streams; or the break-through of some impervious barrier or retaining wall.
Although these causative events seem to be widely different, each one effects a significant change in the surface drainage pattern, resulting in stream rearrangement, rejuvenation, diversion, or capture. On this account the theory is termed the "Stream Piracy" theory.
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