SUBMARINE DEPOSITS 191 



by cable-laying ships in the North Atlantic) to accumulate 

 at the rate of about one inch in ten years. 



3. Bed Clay. — This deposit is characteristic of the abysses, 

 the deeper parts of the floor of the ocean, and covers at 

 least 50 millions of square miles at depths of 2, 500 to over 5,000 

 fathoms. It forms the floor of more than half the Pacific. 



It is a clayey deposit composed mainly of hydrated sili- 

 cate of alumina and iron, derived from the decomposition 

 of pumice and other volcanic particles and interstellar dust 

 along with the residue of the dissolved Globigerina shells 

 and other organisms. Quartz particles are rare or absent ; 

 but there are in places, especially in the Pacific, many 

 manganese nodules of all sizes and layers of manganese on 

 pumice, sharks' teeth, whales' ear-bones, etc. The red 

 colour of the clay is due to ferric oxide and peroxide of 

 manganese, derived from the decomposition of volcanic 

 rocks. Typical Red Clay is, then, a non-calcareous deposit, 

 although it passes gradually into the calcareous Globigerina 

 ooze of less deep water. It also passes insensibly into 

 Radiolarian ooze in some locaHties where these sihceous 

 organisms are present in quantity on the surface of the 

 sea. It is the most widely distributed of all the pelagic 

 deposits, and the floor in the deepest parts of every ocean, 

 beyond the range of Globigerina ooze, is covered by this 

 stiff reddish-brown clay. It is as characteristic of the 

 deeper Pacific as Globigerina ooze is of the rather shallower 

 Atlantic. The Red Clay of deep water in the South Pacific 

 is probably accumulating at a very slow rate. According 

 to Murray, at " possibly not more than a foot since Tertiary 

 times." 



It is usually considered that there is no rock in the geo- 

 logical series which would correspond to consoUdated Red 

 Clay, and this is one of the arguments that has been used 

 in support of the view that at least the deeper parts of the 

 great ocean basins have been permanent for long periods 

 of time. 



