324 



HblKZKN AND LAUUHTON 



[chap. 14 



runs east-west at 40°N latitude. As the result of a recent detailed study, 

 Hurley (1960) has been able to divide the northeast Pacific into four separate 

 plains (Fig. 8). 



The Alaskan I'laiii lies at the base of an extensive continental rise which 

 extends from the eastern end of the Aleutian Trench to the southern tip of the 

 Queen Charlotte Islands (Menard and Dietz, 1951). This continental rise is 

 interrupted by a series of seamounts. The Alaskan continental rise is crossed by 

 several well nia])ped dee])-sea channels, several of which can be shown to be the 

 seaward extensions of continental slope submarine canyons. Centered along 

 150°W longitude is a low. irregular rise punctuated by many large seamounts. 

 The Alaskan Abyssal Plain lies between the base of the Alaskan continental 

 rise and the eastern edge of this oceanic-rise area. An east-west line of sea- 



Sea level 

 500 



Vertical exaggeration x 200 



100 200 300 



Nautical miles 



8m/km 4m/km 2m/km 



1000 ^ 

 o 



SI 



1500 2 



c 

 2000 ^ 



0) 



Q 



2500 



3000 



Im/km 

 0.5 m/km 



Fig. 9. Long profile of the northeast Paeific abyssal plains and continental rise. The 

 Aleutian Abyssal Plain lies west of C. Immediately east of C are the steeper gradients 

 of the abyssal gap which connects the Tufts and Alaska Abyssal Plains with the 

 Aleutian Abyssal Plain. East of the steeper gradients of this gap are the abyssal-plain 

 gradients of the Tufts and Alaska Abyssal Plain. Immediately to the west of A and B 

 typical steep gradients of the continental slope drop to the lower gradients of the 

 continental rise. (After Hurley, 1960.) 



mounts and ridges at about 50°N separates the southern edge of the Alaskan 

 Abyssal Plain from the Tufts Abyssal Plain, which lies to the south. 



The Tufts Abyssal Plain is bounded on the south by the Mendocino Rise, on 

 the east by the ridge and trough province, and on the northwest by the same 

 oceanic rise which forms the western boundary of the Alaskan Abyssal Plain. 

 The Alaskan Abyssal Plain is connected by several abyssal gaps to the Tufts 

 Abyssal Plain. On the western boundary of the Tufts Abyssal Plain two distinct 

 interplain channels, the Horizon Channel and the Mukluk Channel, pass through 

 a broad abyssal gap connecting the Tufts Plain to the lower-lying Aleutian 

 Abyssal Plain to the west (Fig. 9). 



East of the ridge and trough province, which runs from Cape Mendocino to 

 the southern tip of the Queen Charlotte Islands, lies the Cascadia Abyssal Plain. 



