UNDER PLANETESIMAL HYPOTHESIS 



7. Gradational stage. To complete the survey of stages, it 

 is necessary to note that after the growth of the earth had nearly 

 ceased, and volcanic action had passed its climax, the surface was 

 no longer subject to universal burial, but was exposed, age after age, 

 to the action of air and water. The material removed by these 

 agents from the higher parts was deposited in the basins. Through- 

 out all the remaining part of this stage, the dominant geologic 

 processes were gradational. Vulcanism and diastrophism continued 

 to be important, but not dominant. This stage embraces the Pro- 

 terozoic and later eras. 



These stages of the earth's history may be grouped as follows: 



111. Kon of Dominant Gradational | Cenozoic Era 

 Processes (the well known J Mesozoic Era 

 eras ) Paleozoic Era 



[ Proterozoic Era 



II. Kon of Dominant Extrusive 

 Process UransUi,,, I. 



ownTa) 



I. Kon of Dominant Formational 

 Processes (hypothetical) 



portion 

 a) The buried portion 



Initial life stage 

 Initial hydrospheric stage 

 Initial volcanic stage 

 Initial atmospheric stage 



Nuclear stage (Early nuclear growth) 

 Nebular stage 



