722 INDEX oceans (continued) abyssal hills 5:384-386, 5:386f fault scarps 5:384f9 5:385f general discussion 5:383 transform faults 5:375, S:386f volcanic growth faults 5:386f, 5:386-387 fractional crystallization 3:215-216 global distribution 3:206f granitic rocks 3:237t hydrothermal vents 5:373-375 mantle convection 4:348 mantle plumes (hotspots) 3:339 melting processes decompression melting 3:210 flux melting 3:212 general discussion 3:210 pressure-temperature diagram 3:211 f propagating rifts 5:396-405 bookshelf faulting 5:396, 5:398, S:404f causal mechanisms 5:398, S:399f continental propagators 5:402f, 5:403, 5:403f, 5:404f evolution 5:396 implications 5:403 microplates 5:398, 5:400f, 5:401f oceanic propagators 5:396, 5:396f, 5:397f pseudofaults 5:396, 5:396f ridge segmentation axial depth profiles 5:375f, 5:378f, 5:379f axial variations 5:381f characteristics 5:3 76* discontinuities 5:3 74/", 5:375, 5:376*, 5:377/i 5:378f9 5:3 79f general discussion 5:375 geochemical correlations 5:380f hierarchies 5:3 77f magma supply 5:375, 5:378f9 5:382f mantle upwelling 5:376-377, 5:378f transform faults 5:375, 5:386f, S:396f rift valleys 5:438 seamounts 4:475, 4:477*, 4:479 sea water chemistry 5:96 seismic structure 5:405-417 axial magma chamber 5:407, 5:413f background information 5:405 crustal thickness 5:415f9 5:416f magma chamber depths 5:415 magma-lens reflections 5:416f Mohorovicic discontinuity 5:412, 5:413f seismic layer 2A 5:406 seismic velocities 5:406f, 5:410, 5:411f structural variations 5:414, 5:415f, 5:416f shaded relief map 5:373f spreading centres Atlantic Margin 4:95, 4:97f axial depth profiles 5:3 75f axial variations 5:381f continental drift theory 3:204-205 Eltanin (research vessel) 3:203 Eocene 5:466 faulting processes S:385f gravity measurements 1:101, l:101f morphology 5:373 overlapping spreading centres 5:374f, 5:375, 5:396-405 Pangaea 3:143f propagating rifts 5:396-405 sea floor spreading 1:83f, 3:198, 3:203, 3:204-205, 3:362-363 topography 5:374f, 5:384-386 thermal metamorphism 5:501 North Atlantic Deep Water 5:474-475 ocean basin exploration 3:197 ocean-floor metamorphism 3:392-393 oceanic crust 1:404f axial magma chamber characteristics 5:408f9 5:409f, 5:410, 5:414f crustal structure 5:41 If early research 5:407 schematic diagram 5:413f seismic profile 5:409f seismic velocities 5:410, 5:411f chemical composition determination 1:406, l:406t crustal thickness 5:415f, 5:416f heat flux 5:363* magma chamber depths 5:415 magma-lens reflections 5:416f Mohorovicic discontinuity characteristics 5:412, 5:414f general discussion 5:412 schematic diagram 5:413f mountain-building processes 5:418 plate tectonics theory 1:440f seismic layer 2A characteristics 5:407, 5:408f9 5:409f crustal structure 5:41 If, 5:415f crustal thickening 5:41 Of early research 5:406 geological significance 5:407 seismic velocities 5:406f, 5:415f seismic structure 5:405-417 structural variations 5:414, 5:415f, 5:416f thermal gradients 3:411 f transform faults 5:384, 5:386f transition zone 4:101 f oceanic manganese nodular deposits 5:113-120 compositional variability Atlantic Ocean 4:105, 5:119 general discussion 5:117 Indian Ocean 5:119 Pacific Ocean 5:117, 5:118f distribution Atlantic Ocean 5:117 buried nodules 5:117 general discussion 5:115 geographic distribution 5:116f Indian Ocean 5:117 Pacific Ocean 5:116 economic potential 5:119 elemental abundances 5:114t ferromanganese oxide crusts 4:648, 5:119, 5:76, 5:77f historical background 5:113 internal structure 5:114, 5:115f, 5:116f occurrence 5:113 tertiary diagram 5:115f ocean island basalts 3:339 Pacific Ocean 4:1 petroleum reservoirs 4:235* rudaceous rocks 5:140 thermohaline circulation 4:224, 4:514-515, 4:517f9 4:643-644, 5:464, 5:470-471, 5:489 ocean trenches 5:428-437 accretionary wedges 5:307-317 controlling factors 5:317t critical taper 5:309f decollement 5:309, 5:309f9 5:310f, 5:311f95:315f95:316f fluid flow 5:312, 5:313f fluid pressure effects 5:307, 5:309f9 5:311f, 5:315, 5:316f formation processes 5:307, 5:308f, 5:309, 5:310f95:311f9 5:431-432 major trenches 5:430* methane hydrates 5:312, 5:314f obduction 5:315 oblique subduction 5:315, 5:316f occurrences 5:307 seamounts 5:435f sediment thickness 5:311, 5:312f seeps and vents 5:312 stability 5:3 09f subcretion5:309/",5:314 tectonic erosion background information 5:313 basement topography 5:314, 5:315 f fluid pressure effects 5:315, 5:316f tuxbi6ites5:310f95:311f chemosynthetic communities 5:433-434 convergent plate boundaries 4:343f, 4:344, 4:345fy 5:429f, 5:429-430 critical taper 5:433 depth control factors 5:435 early research 5:428 empty trenches 5:434 faulting 5:435f, 5:436f filled trenches 5:432 geographic distribution 5:430, 5:430f island arcs 5:431 maximum depth 5:430* morphology 5:431, 5:43If Oceania 4:109 outer rise 5:434 sediment transport 5:432 subduction erosion 5:431-432, 5:434, 5:435f water volume 5:433