. Elementary physical geography . Fig. rocks on the plains of Kansas. and 133 and Plate28). They have beenbodily raised withvery little disturb-ance. In mountains,and less prominentlyelsewhere, the rockshave been movedfrom their horizontalposition, and causedto assume inclinedattitudes, which areoften very complex. These changes commonly assume oneof two forms, either (1) fold-ing or (2) breaking, whichwe call faulting. Even the most brittle ofrocks may be folded. Thecause for the folding usuallyacts so slowly, and the rocksare under such pressure fromabove, that they bend, rathe
. Elementary physical geography . Fig. rocks on the plains of Kansas. and 133 and Plate28). They have beenbodily raised withvery little disturb-ance. In mountains,and less prominentlyelsewhere, the rockshave been movedfrom their horizontalposition, and causedto assume inclinedattitudes, which areoften very complex. These changes commonly assume oneof two forms, either (1) fold-ing or (2) breaking, whichwe call faulting. Even the most brittle ofrocks may be folded. Thecause for the folding usuallyacts so slowly, and the rocksare under such pressure fromabove, that they bend, rather than break, when subjected to a strain such as that which comes from contraction of the interior. A simple kind of fold is that known as the monocline (Fig. 91), where the rocks are inclined in only one direction. When they are bent up in the form of an arch, the folds are si s I gl known as anticlines (Fig. 92), FlG 92 and the corresponding down Anticline. fold is known as the syncline. Fig. monocline fold.
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