COAST RECORDS OF THE RISE OR FALL OF LAND 247 



sharp contrast with the new plain. It is therefore referred to as 

 the oldland and the newly exposed coastal plain as the newland 

 (Fig. 272). 



But the near-shore deposits upon the sea floor had an initial 

 dip or slope to seaward, and this inclination has been increased 

 in the process of uplift. The streams from the oldland have 

 trenched their way across these deposits while the shore was ris- 

 ing. But the process being a slow one, deposits have formed 

 upon the seaward side of the plain after the landward portion was 

 above tide, and the coastal plain may come to have a " belted " 

 or zoned character. The streams tributary to those larger ones 

 which have trenched the plain may encounter in turn harder and 

 softer layers of the plain deposits, and at each hard layer will be 

 deflected along its margin so as to 

 enter the main streams more nearly 

 at right angles. They will also, as 

 time goes on, migrate laterally sea- 

 ward through undermining of the 

 harder layers, and thus will be FIG. 273. ideal form of cuestas 

 shaped alternating belts of lowland f nd intermed | ate lowlands carved 



from a coastal plain (after Davis). 



separated by escarpments in the 



harder rock from the residual higher slopes. Belts of upland of 



this character upon a coastal plain are called cuestas (Fig. 273) . 



The sudden uplifts of the coasts. Elevations of the coast 

 which yield the coastal plain must be accounted among the 

 slower earth movements that result in changes of level. Such 

 movements, instead of being accompanied by disastrous earth- 

 quakes, were probably marked by frequent slight shocks only, 

 by subterranean rumblings, or, it may be, the land rose gradually 

 without manifestations of a sensible character. 



Upon those coasts which are often in the throes of seismic dis- 

 turbance, a quite different effect is to be observed. Here within 

 the rocks we will probably find the marks of recent faulting with 

 large displacements, and the movements have been upon such a 

 scale that shore features, little modified by subsequent weathering, 

 stand well above the present level of the seas. Above such coasts, 

 then, we recognize the characteristic marks of wave action, and 

 the evidence that they have been suddenly uplifted is beyond 

 question. 



