140 



DEPTHS OF THE OCEAN 



Largest 

 deejDS. 



Valdivia 

 Deep. 



the Atlantic, and one partly in the Atlantic and partly in the 

 Indian Ocean. From the point of view of depth the Challenger 

 Deepest Deep in the North Pacific and the Aldrich Deep in the South 

 deeps. Pacific are the most important, for only these two include 



depths exceeding 5000 fathoms, while in eight other deeps 

 depths exceeding 4000 fathoms have been recorded. On the 

 other hand, in some cases the deeps enclose low rises, on which 

 the depth is less than 3000 fathoms. The deeps vary in form 

 and size to a most extraordinary degree, and future soundings 

 may show that some of them should be subdivided into two or 

 more portions, or that two or more deeps as now laid down 

 should be united into a single deep. 



From the point of view of superficial area, the most im- 

 portant deeps are the Valdivia, Murray, Tuscarora, Wharton, 

 Nares, Aldrich, and Swire Deeps, which are estimated to cover 

 in each case an area exceeding 500,000 square miles. In the 

 following paragraphs the principal deeps of the world are briefly 

 characterised, arranged in the order of magnitude : — 



Valdivia Deep lies in the far south, partly in the Atlantic 

 and partly in the Indian Ocean. It is based principally on 

 soundings taken by the German Deep-Sea Expedition on board 

 the "Valdivia," and has a maximum depth of 3134 fathoms. It 

 is estimated to cover a total area of 1,136,000 square miles, 

 nearly one-half of which (523,000 square miles) lies to the west 

 of long. 20° E., i.e. within the Atlantic basin, while the remain- 

 ing half (613,000 square miles) lies to the east of that meridian, 

 and is therefore in the basin of the Indian Ocean. The outline 

 of this deep, especially in its western portion, is largely hypo- 

 thetical, and future soundings may modify the area assigned to 

 it at present. 

 Murray Murray Deep, situated in the Central North Pacific between 



^'^'^P- lat. 25" and 40° N., is estimated to cover an area of about 



1,033,000 square miles, and is founded on soundings taken 

 partly by the "Challenger" Expedition. The maximum depth 

 recorded in it is 3540 fathoms, and there is a small area within 

 the deep in the vicinity of this deepest sounding where depths 

 of only 2800 and 2900 fathoms are recorded. 

 Tuscarora Tuscarora Deep lies in the North- Western Pacific, and is of 



Deep. elongated form, extending from the Tropic of Cancer north- 



eastwards to near the Aleutian Islands in lat. 52° N., approach- 

 ing to within a comparatively short distance of the shores of 

 Japan and the Kurile Islands. Its area is estimated at 908,000 

 square miles, and the maximum depth is 4655 fathoms, recorded 



