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V.—On the Formation of Ravines by Recent Drift Accumulations

Published online by Cambridge University Press:  01 May 2009

Extract

It is not unusual in drift deposits, banked on hill slopes, to find a deep cut occupied by a very minute stream. These outs or ravines are supposed to be due to the streams; having been excavated by them in the banks of drift. If a ravine of this class is formed in one of the older drifts—namely, the Boulder-clay-drift or the Moraine-drift—it must apparently have been cut by a stream, but much of the drift banked on hill slopes is quite recent; that is formed by meteoric abrasion, and being added to at the present day. In these recent drifts, ravines are of common occurrence, and I would suggest that, instead of the stream cutting its ravine, meteoric abrasion has heaped up the banks, and the only action capable of being done by such a stream, is to keep its channel clear. Such accumulations of drift are very frequent in association with Maums, or connecting gaps across mountain-ranges, and there are always ravines in the banks,—yet by no arrangement of the water-supply, could streams be formed that would have the power to excavate them. In the accompanying sketch of Maumgeeha, Yar-Connaught, there is a maum, below which is a recent drift-bank with a ravine and its accompanying stream. None of the surface drainage of the hills on either side of the maum can get into the stream, it being fed by a spring, while the surface drainage of the mountains flows as represented by the arrows, and yearly the shed from the hills adds to the height of the banks.

Type
Original Articles
Copyright
Copyright © Cambridge University Press 1869

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