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Updated: May 3, 2025
Is the fault a STRIKE FAULT, i.e. one running parallel with the strike of the strata, or a DIP FAULT, one running parallel with the direction of the dip? Is the fault a strike or a dip fault? Draw a second diagram showing the same block after denudation has worn it down below the center of the upthrown side. This exercise may be done in blocks of wood instead of drawings.
We must, however, bear in mind that in the natural section or sea-cliff we only see the foldings imperfectly, one part being invisible beneath the sea, and the other, or upper portion, being supposed to have been carried away by DENUDATION, or that action of water which will be explained in the next chapter.
They observe that no gold has yet been found in the Permian conglomerates which lie at the base of the Ural Mountains, although large quantities of iron and copper detritus are mixed with the pebbles of those Permian strata. Hence it seems that the Uralian quartz veins, containing gold and platinum, were not formed, or certainly not exposed to aqueous denudation, during the Permian era.
It has been suggested that the stripping off by denudation of dense masses from one part of a continent and the delivery of the same into the bed of the ocean must have a decided effect in causing changes of temperature in the earth's crust below, or, in other words, in causing the subterranean isothermals to shift their position.
Superficial Signs of the same obliterated by Denudation. Great Faults the Result of repeated Movements. Arrangement and Direction of parallel Folds of Strata. Unconformability. Overlapping Strata. Hence it follows, that what is now dry land was once under water.
Long lines of tree-covered hills raised some 600 or 700 feet above these valleys of denudation, prevent the scenery from being monotonous. Large game is abundant. Elephants, buffaloes, and zebras grazed in large numbers on the long sloping, banks of a river called Chiséra, a mile and a half broad. In going north we crossed this river, or rather marsh, which is full of papyrus plants and reeds.
The consideration of these facts impresses my mind almost in the same manner as does the vain endeavour to grapple with the idea of eternity. I am tempted to give one other case, the well-known one of the denudation of the Weald.
Every one must admit that the upper valley of the Rhone has been chiefly caused by fluviatile denudation, and it is obvious that the quantity of matter removed from that valley previous to the glacial period would have been amply sufficient to fill up with sediment the basin of the Lake of Geneva, supposing it to have been in existence, even if its capacity had been many times greater than it is now.
Denudation and the action of ice in the glacial epochs have worn through the hard upper stratum, and formed the long and narrow dales; and in Littondale, Wharfedale, Wensleydale, and many other parts, one may plainly see the perpendicular wall of rock sharply defining the upper edges of the valleys.
A similar succession of events has, in all likelihood, occurred in Europe during the deposition and denudation of the loess of the Pleistocene period, which, as we have seen in a former chapter, was long enough to allow of the gradual development of almost any amount of such physical changes.
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