The Primaeval State of the Earth 13 



sharp jump in density when passing to the crust indicates apparently that the 

 core of the Earth consists chiefly of iron and nickel [ii]. 



A fact pointing to the thermal state of the surface layers of the Earth is that 

 the continents are composed chiefly of granite, which consists of three basic 

 minerals : quartz, felspar and mica. It is generally recognized that granite must 

 have formed through the cooHng of hot magma at a temperature not less than 

 1000 °C. The continental granite massif has been growing in volume and area 

 since the very earliest stages of the development of the Earth [12], 



The dynamics of continent formation is far from clear, but in general it should 

 have consisted in the escape of huge quantities of molten siHcate from the 

 interior of the Earth, which was accompanied by the development of platforms, 

 a gradual diminution of geosyncHnes, which was a certain irreversible and 

 gradually relaxing process. 



This process was also accompanied by a gradual decrease in the intensity of 

 volcanic activity. A. P. Pavlov [13] has given us a very vivid picture of how 

 enormous basaltic fields occupying many milHons of square kilometres on the 

 Yenisei, the Tungusk, in Greenland, India, the United States and in other 

 parts of the world were formed in the past as a result of volcanic activity. 



At the present time, the only active zones of vulcanism left are those in the 

 Kamchatka region and the Kurile islands, and also in the Mediterranean. This 

 process of the extrusion of masses of silicate to the surface, the process of forma- 

 tion of a sialitic Earth crust through gradual differentiation, was inevitably 

 accompanied by the production of water vapour that fed the oceans. And this 

 is not all. It may, apparently, be considered that the water of the oceans of to- 

 day must have come from the interior of the Earth chiefly during the cooling 

 period there. According to Grayton [14] the water vapour content in erupted 

 magma of volcanoes may reach 10% in weight. Moreover, Geranson has shown 

 that the granite magma under pressures that correspond to a depth of 10 

 to 20 km is capable of retaining huge quantities of water in solution that make 

 up as much as 10% of the total weight. The ability to hold water falls with the 

 pressure, and the water escapes in the form of vapour. Consequently, any ex- 

 trusion of sialitic material to the surface must inevitably lead to the escape of 

 enormous quantities of water that remains on the quickly cooling Earth and fills 

 the depression between the slightly raised continents. If we consider for a 

 moment that the average depth of the oceans spread evenly over the whole 

 surface of the Earth amounts to approximately 3-4 km, then all that is required 

 for an explanation of the production of this quantity of water from the interior 

 of the Earth is an analogous extrusion of material within the Hmits of a thin 

 20-30-km layer, which exactly corresponds to the external thickness of the 

 Earth's crust. 



All these geological facts are in good agreement with the theory of H. Jeffreys 

 [15] who postulates that the Earth was originally in a gaseous state, but that in 

 roughly 5000 years it could be reduced to a liquid state due to convection 

 currents. And the total energy of condensation to the present radius would be 

 10,000 cal/g. Later, when our planet passed to the solid state, the cooling 

 time was considerably extended until the temperature of the surface at last 



