i8 A TEXTBOOK OF OCEANOGRAPHY 



to volcanic action ; in some cases this action has not been 

 sufficiently pronounced to build up an island, so we have the 

 phenomenon of " submarine peaks." A large number of these 

 appear on the charts ; some of them are so near the surface as 

 to give anchorage to ships. For the most part, these submarine 

 peaks were discovered by cable steamers ; some of them are 

 doubtless due to errors in soundings, and will disappear on 

 further investigation. Six of these peaks are found close 

 together in the angle between Gibraltar, Madeira, and the 

 Canary Islands. In many cases the volcanic origin of these 

 peaks has been proved by the nature of the bottom as revealed 

 by the deep-sea lead. In some instances coral structures are 

 identified, more rarely mud. Some of these peaks have been 

 recorded once only, and the most careful survey has failed to 

 identify them a second time. According to Littlehales, the 

 probability of finding a small submarine peak of a square 

 metre surface is only i in 6,173. 



Steep slopes are also found on the continental rim. 

 According to the hypsographical curve, the area between 

 1,000, 2,000, and 3,000 metres is relatively very small, and 

 from this it follows that there must be steep slopes in these 

 soundings. At the north end of the Bay of Biscay, where the 

 continental shelf ends, there is an Alpine relief to the sea 

 bottom. Thoulet in 1895 spoke of this region as "une veritable 

 falaise." 



The naming of the characteristic features of the ocean floor 

 is very confused. The oldest names, applied, however, only 

 to shallow seas, are the "Banks" and "Grounds" of the 

 fishermen e.g., the Dogger Bank and the Oyster Grounds. 

 The older oceanic names are those of the Atlantic : the Dolphin 

 Ridge of the U.S. Brig Dolphin, and the Challenger Ridge 

 of the Challenger. The earliest bottom chart of the Pacific 

 contains a number of names derived from the exploring ships 

 and their scientific leaders. Other systems rely on geographical 

 names exclusively. 



Sir John Murray adopted a combination of these methods, 



