SECT. 2] 



THE MID-OCEANIC RIDGE 



405 



are shown in Fig. 13. Profile 7 of that figure represents the southeast Pacific 

 crossing. It is conspicuous for the absence of a rift, the smoothness of the rehef 

 across the crest, and the continuous gentle gradient, unbroken by scarps. 





7 WEST 



Fig. 1.3. Eight typical profiles of the mid-oceanic ridge in the North Atlantic, South 

 Atlantic, Indian and South Pacific Oceans. The smooth relief across the crest of the 

 mid-oceanic ridge in the South Pacific contrasts markedly with the rougher topo- 

 graphy of the other oceans. Profile 2 was obtained aboard Crawford and Profile 8 was 

 obtamed aboard Horizon. The remaining profiles were obtained with a Precision 

 Depth Recorder aboard R.V. Vema. (Vertical exaggeration of profiles is 100:1.) 



Fig. 14 (Ewing, Ewing and Talwani, 1963) shows a ridge profile in the North 

 Atlantic, between Dakar and Halifax, based on seismic-refraction (Ewing and 

 Ewing, 1959) and reflection measurements. 



The unconsolidated sediments, whose thickness was measured continuously 



