85. What is the hydrologic cycle? 



The oceans are the vast reservoir from which moisture is drawn to 

 furnish precipitation to the land. Even inland areas, such as the 

 Missouri-Mississippi drainage area, receive up to 90 percent of their 

 precipitation from water that has evaporated from the sea surface. 



It has been estimated that about 9,000 cubic miles of water fall on 

 the land surface of the earth each year. This water dissolves minerals 

 from the earth and carries them, along with sediments, to the ocean. 



Rain water may return to the ocean directly through streams or rivers 

 or more slowly through subsurface percolation. Part of the water may 

 be withdrawn from the cycle for extended periods by being locked up as 

 ice, and some evaporates back to the atmosphere and falls again as rain 

 or snow. 



Thus, the essence of the cycle is the progressive transformation and 

 movement of water through evaporation, precipitation, runoff, and 

 return to the sea. 



King, Cuchlain A. M. 



Oceanography for Geographers, Edward Arnold Ltd. (London), 1962. 

 Pincus, Howard J. 



Secrets of the Sea, Oceanography for Young Scientists, Annerican 



Education Publications, Inc., 1966. 



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