208 THE OCEAN 



miles, especially in the neighbourhood of coral 

 reefs and on the summits and sides of sub- 

 marine elevations far from land. 



8. Diatom Ooze. — This type of deposit is 

 distinguished by the abundance of the frus- 

 tules of diatoms fallen from the surface waters, 

 and occurs in those regions of the ocean where 

 diatoms flourish luxuriantly, notably in the 

 great Southern and Antarctic Oceans, but 

 also along the northern border of the Pacific. 

 When dry the diatom oozes are not unlike 

 dirty flour and appear to be homogeneous, 

 but when they occur in localities affected by 

 floating icebergs there is usually an admixture 

 of larger and smaller mineral particles, some- 

 times even boulders and rock fragments, with a 

 small proportion of the remains of calcareous 

 organisms, principally pelagic foraminifera 

 belonging to one or two cold-water species. 

 This type of deposit covers an estimated area 

 of about ten millions of square miles, forming 

 a nearly continuous band around the south 

 polar regions, with a smaller area in the North 

 Pacific. 



9. Red Clay. — This type is probably the 

 most characteristic and most widely dis- 

 tributed of all the deep-sea deposits. The 

 basis of the deposit is hydrated silicate of 

 alumina and iron, which usually makes up fully 

 half the bulk, there being an admixture some- 



