50 THE OCEAN FLOOR 



is replaced by the so-called red clay, a sediment 

 generally poor in lime but relatively rich in ferric 

 hydroxide and manganese peroxide, which give it a 

 color varying from whitish red to dark chocolate brown. 

 The red clay is estimated to cover not much less than 

 40 million square miles of the deeper and deepest ocean 



Fig. 19. Radiolarian ooze (radiolarit) 



floor. The origin of red clay still offers unsolved prob- 

 lems to submarine geology. Normal components are 

 volcanic material — ash, mineral grains, and water- 

 logged pumice — which has been carried over great 

 distances by surface currents. An admixture of siliceous 

 skeletons from diatoms or radiolarians is not uncom- 

 mon, the latter especially in the equatorial region, where 



