14 UNIFORMITARIANISM AND ACTUALISM 



ing', or of 'revolutions of the earth's crust', when describing that 

 relatively short, relatively unstable period of mountain building which 

 'only' lasted some 50 million years. We like to stress the difference 

 between this later period of mountain building and the earlier, longer, 

 more stable period. In doing so, perhaps for lack of words, perhaps 

 also owing to a sort of laziness, we definitely tend to overstress. We 

 often forget to state explicitly that our catastrophes, the catastrophic 

 events in geological literature, are a far cry from human catastrophes. 

 Our catastrophic mountain building period, to return to the example 

 mentioned, was the ultimate result only of many repeated small-scale 

 movements summed up over 50 million years. 



No geologist will therefore deny the mobility of the earth, or the 

 existence of variations in speed or in intensity of the different pro- 

 cesses in operation on earth. Nevertheless, it forms no objection for 

 him to adhere to an actualistic viewpoint on geologic history, or to 

 use present causes in explaining the past. 



SMALLER CATASTROPHES AND UNIFORMITARIANISM 



To make matters still more difficult to express, in relation to this 

 principle of uniformitarianism, it must be added that even smaller 

 catastrophes, although real enough on our human scale, take their 

 place in this actualistic picture of the geologic past. To take the 

 two examples mentioned above, the biblical deluge and the Plinian 

 eruption of Vesuvius, we feel sure that many similar catastrophes 

 have contributed to the history of the earth. 



Floods, for instance, are quite common smaller catastrophes. They 

 may be the results of quite different physical causes. We have rain 

 floods and river floods, such as in Mesopotamia; tsunamis due to 

 seaquakes, as in the Pacific; storm floods as in the low-lying coastal 

 districts of Holland. These and other causes all produce floods of 

 local catastrophic consequences. Each larger flood, regardless of its 

 cause, may have entered into the saga of a certain tribe, and even- 

 tually might have become extrapolated to effects far beyond that 

 of the original, or schematized into Gospel truth. None of them will, 

 however, at one single time, have altered the earth's surface to any 

 extent. Only when such floods occur repeatedly will they very 

 gradually, acquire geological significance. 



The same can be said for volcanic (>ruptions. Even the Plinian 



