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Clays Cliffs
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The Clay Cliffs are situated on a
lowland tussock property lOkm west of Omarama, on the northern side of the
Ahuriri River. The Ahuriri River is a major tributary of the Waitaki River,
rising deep in the Southern Alps north of Haast Pass. The cliffs can be
viewed across the river from the Lindis Pass highway (SH8). The Clay Cliffs
are a spectacular natural example of "badland" erosion. |
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A combination of high, steep,
sharp, bare pinnacles and ridges separated by deep, narrow ravines and
canyons, this kind of landform develops on certain types of rocks in arid or
semi-arid regions subjected to occasional heavy rainstorms. For badland
topography to form, the rocks must be compact enough to stand in deep faces,
yet soft enough to be readily eroded by running water. The name Clay Cliffs
is actually a misnomer, for the rocks here consist of layers of gravel and
silt. |
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In geological terms the rocks are
quite young. The sediments were deposited by rivers flowing out from the
glaciers that existed one or two million years ago. By contrast, the rocks
of the nearby mountains from which the sediments were derived, are about 250
million years old. Since their deposition, the strata at Clay Cliffs have
been tilted and the individual layers of gravel and silt now form prominent
sloping bands running through the outcrops. |
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Badland topography is not
uncommon in other parts of the world, the most famous examples being in
South Dakota, USA. The term was originally used to describe part of that
region which was difficult to cross. It is now widely used to describe any
landscape characterised by deep dissection, ravines, gullies and sharp
ridges created by fluvial erosion on relatively soft rocks in a semi-arid
environment. |
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Smaller scale, man-made
examples of such erosion are relatively common in the gold sluicings of
Central Otago, for instance at Naseby and Bannockbum. In these areas, gravel
beds, like those at the Clay Cliffs, were eroded by high-pressure jets of
water in order to extract the gold they contained. |
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