AGE OF EARTH AND OCEAN — KNOPF 205 



potassium and sodium. How much of the volcanic chlorides is a 

 new contribution and how much, if any, is " resurgent " is not 

 known. Eecent opinion, indeed, inclines to the view that this 

 chlorine is a new contribution from the primitive earth-stuff. Zies 

 (1928) shows that it is highly probable that — ■ 



the discharge of acid gases from volcanoes is at least of the proper order of 

 magnitude to supply the additional chlorine wl^ich is characteristic of the 

 ocean as compared with the rivers. 



If this is true, as it seems likely to prove, some of the chlorine found 

 in river waters must be of volcanic origin, but how much has not 

 been estimated. 



RATE OF CHEMICAL DENUDATION 



The amount of sodium that is annually supplied to the ocean is 

 influenced by at least four factors: (1) The composition of the rocks 

 of the surficial portion of the earth's crust; (2) climate; (3) area of 

 the continents; and (4) height of the continents. These factors 

 have all varied during geologic time, and therefore the rates of 

 supply of sodium to the ocean must have varied. It is generally con- 

 ceded that the present rate is abnormally high, some surmises being 

 that it is as much as fifteen, or even twenty, times the average for 

 all of earth's history (Barrell). But this conjectured rate applied 

 to the aggregate rate of denudation, i. e,, mechanical plus chemical 

 denudation, and just how much the present rate of chemical denuda- 

 tion exceeds the average rate of chemical denudation for all of geo- 

 logic time has not yet been quantitatively established. 



CONCLUSION 



On account of the many hypothetical and unsolved factors that 

 enter into the determination of the age of the ocean by the sodium 

 method, it can not be used as a check on other methods. The most 

 that can be said is that the estimate of 100,000,000 years for the age 

 of the ocean is probably a minimum. 



REFERENCES 



Artis, B. 



1916. Nitrogen, chlorine, and sulphates in rain and snow. Chem. News, 

 vol. 113, pp. 3-5. 



Bareeli,, Joseph. 



1917. Rhythms and the measurements of geologic time. Bull. Geol. Soc. 

 Amer., vol. 28, p. 749. 



Becker, G. F. 



1910. The age of the earth. Smithsonian Misc. Coll., vol. 56, No. 6, 

 pp. 1-28. 

 Beheend, F., and Berg, G. 



1927. Chemische Geologic, p. 391. 



