OCEANIC DEPOSITS AND BOTTOM FAUNA 25 



10 million square miles of the earth's surface. Thèse deposits 

 are also built up entirely of material derived from the land. 

 Their constituent materials are smaller in size than those of 

 the littoral deposit, but larger, as a rule, than deep-sea deposits. 

 Gravels, sands, and coarse material predominate, but mud is 

 by no means uncommon in grooves and dépressions, especially 

 in enclosed basins. The mechanical effects of érosion are 

 everywhere recognisable, naturally more marked in the 

 shallower régions. Thèse effects are due to waves, and tides, 

 and currents. 



Areas of Oceanic Deposits 



(Expressed as percentages). 



Littoral and shallow-water deposits ... ... 9*1 



Deep-sea deposits (Terrigenous) ... ... I5"4 



Pélagie 



Globigerina ooze ... ... ... 29*2 



Pteropod ooze ... ... ... '4 



Diatom ooze ... ... ... 64 



Red clay ... ... ... ... 36' i 



Radiolaria ooze ... ... ... 34 



75'5 



1000 

 Deep-Sea Deposits. 



Thèse are found on the sea bottom beyond the loo-fathom 

 line down to the greatest oceanic depths. They cover con- 

 siderably more than one-half of the earth's surface and over 

 90 per cent, of the sea-area (see table above). 



Gravels and sands are only met with accidentally in deep- 

 sea deposits, where depths over 100 fathoms are near the land. 

 The chief deposits are muds, clays, and oozes, the last of 

 organic origin. In certain areas the deposits are appreciably 

 affected by the détritus deposited by floating ice. There is in 

 gênerai an absence of the phenomena of érosion. Since sun- 

 light pénétrâtes very little beyond 100 fathoms, it follows that 

 plant remains are scanty except near that limit. Animal life, 



