AGE OF EARTH AND OCEAN KNOPF 203 



ocean has been in part lost to the ocean, whereas the chlorine has 

 steadily accumulated; (2) that the primitive ocean may have con- 

 tained chlorine; or (3) that the chlorine has been supplied througli- 

 out geologic time by volcanic emanations, which are known to con- 

 tain HCl, NH4CI, and other chlorides. 



The supposition that a vastly greater volume of igneous rock than 

 84,300,000 cubic miles has been decomposed appears to be disproved 

 by the following considerations. The volume of sedimentary rock 

 that would have been formed from the decomposition of the 

 84,300,000 cubic miles of igneous rock is 108,000,000 cubic miles. 

 If this volume of rock were spread over the continental platforms, 

 which are 66,000,000 square miles in extent, it would make a layer 

 2.6 km thick. That it can be inferred from the field evidence that 

 such a layer would probably be thicker than is the actual existing 

 discontinuous layer of sedimentary rocks was pointed out by Van 

 Hise, who was inclined to regard 2 km as a high estimate and 1 km as 

 probably nearer the truth. If, in fact, 1 km is nearer right, it 

 strengthens the growing belief that a considerable volume of sedi- 

 ments has been deposited in the deeper parts of the ocean and has 

 thus become lost to the continents. At any rate, the rough agree- 

 ment between the computed volume of sedimentary rocks and the 

 inferred volume on the continents strengthens the hypothesis that 

 the sodium in the ocean has been largely supplied by erosion of the 

 lands. 



Some sodium is lost from the ocean by the formation of glauconite, 

 for analj^ses of glauconite show up to 3 per cent of NaoO. The so- 

 dium thus lost would appear to be small, however. Sodium is also 

 lost by the formation of albite (NaAlSisOg) in limestones and dolo- 

 mites (Spencer) ; but the amount thus lost, while more than com- 

 monly suspected, is probably small. 



A much greater loss of sodium is due to its removal from the ocean 

 by adsorption and base exchange. Comparison of average analyses 

 of clays shows that marine clays contain much more soda than fresh- 

 water clays, which difference is interpreted by Stremme as due to 

 adsorption of sodium from the water of the ocean. That adsorption 

 or base exchange actually occurs at the bottom of the ocean is indi- 

 cated by the strong increase in the soda content of the palagonite 

 formed by alteration of basaltic glass — the soda content has increased 

 from 1.83 to 4.50 per cent. Chamberlin also has strongly argued 

 for the importance of adsorption in removing sodium from the ocean. 



The properties of the artificial compounds known as permutites 

 appear to be highly significant to the problem of the removal of 

 sodium. The sodium permutite has the composition Na20-Al203- 

 4Si02-xH20; when hard water is run through a filter of sodium 



