100 HISTORY OF THE OCEANS 



But however this may be, the probability is that living processes 

 are very early, and this quite apart from still disputed evidences 

 of early Archean fossils, for the elementary reason that no sure 

 evidence has yet been found for any differences between the 

 surface geochemical processes occurring at the earliest dates 

 accessible to us and those that occur today. And this, despite a 

 certain amount of rather doubtful evidence from isotope distri- 

 bution, would seem to indicate that we have plenty of time, I 

 should say about three or four rather than one billion years to 

 account for the origin of life. 



Of course, what I say may be upset at any time if new evidence 

 comes forward from other isotope studies as to a regime in rock 

 formation, particularly in regard to the state of oxidation of iron 

 and sulfur which would seem to indicate a different regime; but 

 until this does come, I think we would be on safer ground in 

 pushing back the origin of life as far as we can. The absolute date 

 does not matter so much. The essential is that there should be 

 time enough for the formation of the basic chemicals out of which 

 living systems are formed. 



In my opinion the major difference between the early stages 

 and the present is the comparative absence of the hydrosphere or 

 the oceans. The evidence presented at this congress seems to 

 indicate that the earth's crust has undergone a very considerable 

 degree of reworking over the known part of geological history, and, 

 if I am right, also over a long preceding period. The result of this 

 must have been the liberation of a great deal of water from the 

 lower parts of the crust and even the of mantle of the earth. I 

 believe the mechanism for this is very deep seated, at least as 

 deep seated as the deep focus earthquakes, say 700 km down. 

 Here, as we now understand, the rocks are not of the familiar 

 crystalline types but must be of an ultradense type; for example, 

 the olivine of most of the basic rocks is converted into a spinel. 

 All these rocks contain a considerable amount of water and 

 nitrogen, and this will be liberated gradually by the orogenic 

 processes that have taken place in various cycles, possibly as 

 many as sixty cycles, since the first formation of the crust. 



This would mean the gradual growth of oceans, not as rapid as 



