. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. Fig. 29. Fig. Fig. 31. as in Figure 29. The meanders further up-stream continue their advance and the meander uext to the ledge is therefore compressed to a relatively strong curvature, as in Figure 30. The defended cusp is now sharp- ened. It may come to point somewhat up the valley. The compressed meander cannot slip by the ledge ; there is no escape for the stream save by a short- cut across the narrowing flood- plain lobe at time of high water; thus the condition of Figure 31 will in due time be developed. A
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. Fig. 29. Fig. Fig. 31. as in Figure 29. The meanders further up-stream continue their advance and the meander uext to the ledge is therefore compressed to a relatively strong curvature, as in Figure 30. The defended cusp is now sharp- ened. It may come to point somewhat up the valley. The compressed meander cannot slip by the ledge ; there is no escape for the stream save by a short- cut across the narrowing flood- plain lobe at time of high water; thus the condition of Figure 31 will in due time be developed. A rather sharp cusp, one of whose sides faces up the valley, will be produced, and the great concave scarp adjacent to it will have an abandoned channel at its base. Terrace Fronts near Defended Cusps. The difference between the behavior of slipping and of compressed meanders may be inferred to depend on the position of the obstructing ledge with regard to the apex of the meander. If the ledge is discovered near the apex of the meander, the stream may slip past the obstacle, as in the example first given. If the ledge is encountered near the point of river inflexion — that is, on the tangent between two meanders, — compression of the meander up-stream from the obstacle is likely to result. In both these cases the defended cusp is likely to be associated with several short curves and free blunt cusps for a little distance down- valley ; while a rather long re-entrant curve usually joins its up-valley. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Harvard University. Museum of Comparative Zoology. Cambridge, Mass. : The Museum
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