ACTUALISM IN EARLY PROCESSES 65 



face, volcanisni. Typical exogenic processes are weathering, erosion, 

 soil formation, transportation by rivers and sedimentation in lowlands 

 and oceans. 



Now we may state that, in a general way, all exogenic processes 

 are influenced by the composition of the contemporary^ atmosphere. 

 The proposed usage of the terms pre-actualistic and actualistic thus 

 can be extended from the atmosphere to all contemporary exogenic 

 processes. 



The distinction between primeval, anoxygenic and pre-actualistic 

 atmosphere and a later oxygenic and actualistic atmosphere must not, 

 however, be applied to the contemporary endogenic processes. Neither 

 mountain-building nor the formation of a granite batholite, for in- 

 stance, are influenced by the composition of the atmosphere. This 

 is not a theoretical consideration only. For instance, mountain-build- 

 ing, one of the main endogenic processes, in younger geological 

 periods always seems to follow a certain set pattern of events. In this 

 pattern first very thick sediments are laid down in a definite basin, 

 in which the crust slowly subsides; the so-called geosyncline. There- 

 upon follows the folding of these sediments, and finally the subse- 

 quent crustal rising which, in fact, forms the real mountains. This 

 sequence, called the orogenetic cycle, is the main theme, for instance, 

 of Umbgrove's pulse of the earth (p. 12). Similar sequences, oro- 

 genetic cycles which, as far as we are able to study them in the 

 present state of the art of geology, are identical in their main succes- 

 sion to those of younger geologic history, occur far back in the history 

 of the earth. They are found way back to the oldest crustal rocks 

 dated as yet. In contrast to the difference postulated between the 

 early and the present atmosphere and contemporary exogenic pro- 

 cesses, there is no such fundamental difference in the endogenic pro- 

 cesses. As far back as we can see, endogenic crustal processes have 

 been quite comparable to those found in the younger geologic history. 

 Endogenic processes, for all we know, are actualistic as far back as 

 the oldest rocks dated. 



ACTUALISM IN EARLY EXOGENIC AND ENDOGENIC PROCESSES 



We will see further on that the transition from the primeval pre- 

 actualistic atmosphere to the present actualistic one may be pro- 

 visionally dated as having occurred between 2 billion and 1 billion 



