CONTINENTAL STRUCTURES AND PROCESSES AND SEA-F1 



Figure 11-4— CONTINENTAL DRIFT 



TODAY 



In 1912 Wegener noted the striking similarity in the shape of the coastline of the 

 Americas and of Europe and Africa. He suggested that at one time there had been 

 a single supercontinent as shown in the upper left of the figure. Wegener postulated 

 that the landmass broke up and allowed the continents to drift apart as shown in the 

 upper right until they assumed the position of today. 



The same applies to sediment 

 cumulations and potential depths of 

 gas accumulation in such regions as 

 the North Sea, where reserves of 

 natural gas are now a substantial fac- 

 tor in the economies of neighboring 

 countries. 



Thermal Water — An example of 

 the possibility of unexpected return 

 from the study of major crustal proc- 

 esses is seen in the power potential of 

 the thermal waters of the Salton Sea 

 area in California. Lower California 

 is splitting off from the mainland by 

 the same process of sea-floor genera- 

 tion as in the mid-Atlantic — namely, 

 by the upwelling of hot rock materials 

 from depth. This zone of upwelling 

 and splitting apart continues up the 

 Gulf of California and into the conti- 

 nental region underlying the Imperial 

 Valley, undoubtedly causing the great 

 fault systems that have produced the 

 California earthquakes. 



The heated waters resulting from 

 thermal upwelling represent a great 

 power potential. It is estimated, for 

 example, that the power potential in 

 the Salton Sea, Hungary, and other 

 regions where there are large, deep 

 reservoirs of heated water is of the 

 same order of magnitude as the 

 known oil reserves of the earth. 

 Steamwells and natural geothermal 

 heat have been exploited commercially 

 in volcanic regions of Italy, Iceland, 

 and New Zealand, and on an experi- 

 mental basis in the Salton Sea area. 



as great as in comparable regions of 

 Africa. Prospecting for mineral belts 

 in northeastern Brazil, the Guianas, 

 and southern Venezuela in areas as- 

 sumed to be extensions of African 

 belts has begun to disclose similar 

 deposits. 



Petroleum and Natural Gas — Sim- 

 ilarly, where continents have been 

 broken apart by rifting motions with 

 the development of a seaway, the new 

 edges are subject to the deposition of 

 shelf-type sediments. Prior to the 



understanding of continental drift, 

 many of these continental shelves 

 were believed to be ancient. Now it is 

 known that all such new edges are 

 bounded by thick sections of younger 

 sediments which may have oil-bearing 

 potential. This knowledge, coupled 

 with the geological information pro- 

 vided in anticipating depths of drilling 

 as well as structures, has led major oil 

 companies to undertake a worldwide 

 prospecting program. The result has 

 been the discovery of new areas of 

 economic importance. 



Environmental Pollution 



Nature is the greatest polluter of 

 the environment. Geochemical proc- 

 esses have concentrated radioactive 

 elements at the surface, so that man 

 is constantly bombarded by a gamma- 

 ray flux much larger than the average 

 for the earth as a whole. Streams and 

 rivers carry rock flour from the action 

 of glaciers in high latitudes and 

 hydrated ferric oxides, clays, and 

 other debris in lower latitudes to such 

 an extent that deltaic and coastal de- 

 posits cause problems for shipping 



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