SECT. 2] ABYSSAL PLAINS 327 



Arabian Sea. The India Abyssal Plain occupies an area 100,000 mi^ of the 

 eastern Arabian Sea. East of the Somali coast a large abyssal plain extends from 

 4°N to 7°S. The Mozambique Abyssal Plain sloping north to south between 

 approximately 28° and 34°S lies between 37° and 40°E to the south of the 

 Mozambique Channel. 



East of Madagascar the Malagassy Abyssal Plain lies between approxi- 

 mately 12° and 25°S and extends over approximately 3° of longitude. 



An extensive abyssal plain lies west of Australia. Its limits are ill defined but 

 it appears to be centred between 20° and 30°S. 



An extensive abyssal plain extends along the base of the continental rise 

 in the Great Australian Bight. This plain probably exceeds 70,000 mi 2 in area. 



F. Arctic Ocean 



An extensive abyssal plain has been reported in the Canada Basin. It is 

 probable that this abyssal plain, which may have an area exceeding 150,000 mi"2, 

 is fed by the Mackenzie River. The Arctic Ocean is divided by three ridges or 

 rises : (1) the Alpha Rise, (2) the Lomonosov Ridge and (3) the Arctic extension 

 of the mid-oceanic ridge (Heezen and Ewing, 1961). Much of the area between 

 each of these ridges is probably occupied by abyssal plains. The pioneering 

 work of the U.S.S. Nautilus and U.S.S. Skate has shown that abyssal plains 

 exist in the Canada Basin between the Alpha Rise and the Canadian- Alaskan- 



°'' ^Il^S^ LOMONOSOV GR EENLAND-S PITSBERGEN 



O-^ RiDGE STRAITS 



^ j(j^l5_ CANADA ABYSSAL PLAIN . CANADA AP ALPHA RIDGE SIBERIA) I POLE ABYSSAL MID-OCEANIC RIDGE 



C AP_y y PLAIN 



Fig. 10. Abyssal plains of the Arctic Basin. This profile, made by the submarine Nautilus, 

 indicates the presence of three extensive abyssal plains in the Arctic Basin: the 

 Canada Abyssal Plain, the Siberia Abyssal Plain and the Pole Abyssal Plain. 

 (Modified after Dietz and Shumway, 1961.) 



Siberian side (Fig. 10), between the Ali3lia Rise and the Lomonosov Ridge, 

 and between the Lomonosov and the Arctic extension of the mid-oceanic ridge 

 (Dietz and Shumway, 1961). It is probable that an abyssal plain also lies 

 between the mid-oceanic ridge and the Barents Sea continental shelf, but it has 

 not been mapped as yet. Recent soundings by H. Kutschale from Arlis Ice 

 Island have revealed mid-ocean canyons in the Siberia Abyssal Plain. 



a. The Norwegian Sea 



An abyssal plain exists in the Norwegian Sea between the Norwegian con- 

 tinental rise and the mid-oceanic ridge. It is not known at present whether an 

 abyssal plain lies between Greenland and the mid-oceanic ridge. 



