THE PENEPLAIN 847 



lower formations. (See Figs. 219 and 220.) The dome and basin 

 have generally a definite relation to each other. Thus in Europe 

 the Weald dome lies north of and immediately adjacent to the 

 Paris Basin, while in North America the Michigan Basin is sur- 

 rounded by domes. As already outlined in the preceding chapter 

 (see map, Fig. 192), these domes and basins suffered simultaneous 

 deformations at at least two distinct periods, but some of the 

 domes and perhaps some of the basins may have suffered repeated 

 deformations throughout Palaeozoic time. 



6. The Syncline. 



This corresponds to a much elongated basin, and the charac- 

 teristics it exhibits will be essentially those of the basin except that, 

 instead of radiality or concentric arrangement, many of the features 

 will be characterized by parallelism of arrangement. The charac- 

 teristics of synclines as of anticlines are best exhibited in the Appa- 

 lachian region of North America and the Jura Mountains of 

 Europe. 



7. Erosion Features in Faulted Strata. 



These have already been discussed, to some extent in Chapter 

 XX. Some special features are shown in Figs. 221 and 222. 



8. The Completion of the Cycle. 



The Peneplain. When the surface of a country is worn to so 

 low a relief that the streams have practically ceased eroding and 

 are throughout in a graded condition, the surface of the region may 

 be considered as in the peneplain state. This is by no means a per- 

 fectly level surface, but rather one of a rolling or undulating topog- 

 raphy, and not infrequently erosion remnants or nionadnocks rise 

 considerably above the general level of the peneplain. Since streams 

 erode their beds until every portion is graded, the stream bed repre- 

 sents a continuous gentle slope to sea-level. As long as the rela- 

 tive position of land and sea remains stable, reduction of the relief 

 will progress, and the surface of the land will approach closer and 

 closer to the level of the sea. If that could be reached, the region 

 would be reduced to base-level. It is obvious, however, that as the 

 relief is reduced more and more, the rate of reduction rapidly de- 



