33. What are seamounts? How are they created? 



Seamounts are relatively isolated features rising from the deep sea 

 floor. To qualify as a seamount, a rise must be at least 1,000 meters 

 above the surrounding topography. At least 1,400 seamounts have been 

 discovered in the Pacific Ocean; this may be only a small percentage of 

 the seamounts that will eventually be discovered. 



The origin of seamounts is controversial. Their distribution in linear 

 chains gives credence to the theory that they are caused by fissure erup- 

 tions. There is also speculation that seamounts were volcanoes that 

 once extended above the ocean surface and later sank because of their 

 weight. 



Photographs of seamount surfaces show ripple marks which are ap- 

 parently caused by deep currents; samples dredged from North Atlantic 

 seamounts also indicate that they have never been near the ocean surface. 



In the Pacific Ocean many flat-topped seamounts, known asguyots, 

 have been found. A Princeton University geologist. Dr. Harry H. Hess, 

 discovered guyots in the examination of echo sounder records while 

 in command of a naval vessel during World War II. He explains the flat 

 tops as wave erosion at sea level. If this is correct, there has been a 

 great change either in the ocean floor or in the sea level, because the 

 tops of the guyots are now 2,000 to 3,000 feet below the surface. 

 Guyots are unknown in the Atlantic. 



Ericson, David B., and Goesta Wollin 



The Deep and the Past, Alfred A. Knopf, 1964. 

 Gaskell, T. F. 



World Beneath the Oceans, American IVluseum of Natural History, 



1964. 

 Stewart, Harris B., Jr. 



Deep Challenge, Van Nostrand, 1966. 



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