SOLUTION OP THE CLIMATE PROBLEM RAMSAY 239 



The relief of the continents has also changed in accord with the 

 orogenic rhythm, a fact of special interest for the theory put forward 

 in this paper. 



The mountain folding, and all events in connection with it, 

 brought the various parts of the earth's crust into positions which 

 no longer corresponded to the previously existing isostasy. In con- 

 sequence of this, there was again a tendency to new isostasy, re- 

 sulting in elevations here and depressions there. These displace- 

 ments were greatest after the diastrophism at the end of each cycle, 

 while features hitherto prevailing in the aspect of the continental 

 blocks were replaced by new ones. 



The great disturbances enormously changed the relief of the 

 foregoing period. Thus, at the beginning of a new cycle, not only 

 were the land areas greater than at other times, they were also 

 more elevated, and it was then that the loftiest momitains rose on 

 the continents. Then, too, the sea had its greatest depth. For 

 only so could it, in spite of its reduced area, contain the same 

 masses of water. 



The Quaternary period and the Recent time belong to such an 

 era of high continents and deep oceans. The mountains, only 

 formed in the later part of the Tertiary period, are still lofty, and 

 in all continents there are old peneplains in which a young erosion 

 has carved new valleys. This phenomenon is so common that all 

 examples of typical peneplains referred to in literature are pre- 

 Quaternary ones. This signifies, first, that before the crustal 

 movements by which the different portions of the continents came 

 in their present level, the land masses had been in a state of relative 

 repose for so long a time that they were completely degraded, and 

 secondly, that the altitude of most parts of the continents is at 

 present greater than in the pre-Quaternary time. Indeed, we find 

 undisturbed Tertiary marine deposits at high levels, and the most 

 elevated of them belong to the oldest Tertiary beds, while younger 

 occur at lower levels. Even Pliocene deposits lie at many places 

 high above the beaches of both recent and Quaternary seas. 



It is not astonishing that the elevation of the continents, with 

 their highlands and mountains, reached its greatest altitude in 

 Quaternary time. We may call to mind that tangential movements 

 were still going on during this period in many mountains, and 

 many remarkable faultings are equally young. Further, the now 

 existing valleys were formed in Pliocene and at the beginning of 

 Pleistocene time, as is well known and often emphasized. It is 

 very probable, as Nansen^ suggests, that in consequence of this 

 erosion the mountain-ridges may have been raised by isostatical 



' Fridtjof Nansen, " The Strandflat and Isostasy " ; Videnskabsselskabets Skrifter : I. 

 Mat. naturv. Klasse, 1921 ; No. 11, Kristianla, p. 305. 



