176 



INDEX 



Subcrustal weakness, 43 

 Submarine canyons. See Canyons 

 Submarine mountains, 5, 48 



Alpine type, 98 



volcanic. See Volcanic islands 

 Submarine valleys See Canyons; Fur- 

 rowing 

 Sub-oceanic crust 



largely simatic, 19, 27, 61 



strength of, 62 ff 



structure of, 21 



thickness of, 33, 78 

 Subsidence of volcanic piles, 75 

 Substratum 



density of, 85 



secular change of, 58 



simadc nature of, 17 



source of volcanism, 57 ff, 97 



viscosity of, 59 



vitreous or glassy, 57 



weakness of, 57, 97, 98, 157 



world-circling, 57 

 Sumatra Island, 89 

 Super-elevation of continents in relation 



to submarine canyons, 129 

 Surface (seismic) waves, velocides of, 



20, 21 

 Surface-shear waves, 17, 20 

 Susquehanna River, in relation to shelf 



"channel," 119 

 Suva Diva atoll, map of, 67 

 "Swells," submarine, 9 

 Synthesis, a tool of science, 2 



_L agula Island, 68 



Tahiti Island, relation to Bora Bora Is- 

 land, 75 



Tanimbar Island, deformed rocks in, 89 



Taut-wire control, 7 



Temperature 



a cause of weakness in rocks, 32, 44, 



45, 78 



initial, of lava, 56 



origin of volcanic, 56 

 Tertiary Era, 88 

 Tests of isostasy 



in Fennoscandia, 34 ff 



in northeastern North America, 44 

 Tests of theory of submarine valleys, 



138 ff, 147 ff 



Texas, continental terrace off, m 



Thalassic islands, 9, 48 



Tide-gages, showing recent changes of 



level, 39, 44 

 Tiladummati Bank, test of prolonged 



crustal stability, 72 

 Till on Georges Bank, 152 

 Timor Island, 89, 92, 95 

 Tonga Islands, continental rocks in, 23 

 Trinidad Island, deformed rocks in, 95 

 Truk Islands, 67 



Turbulence of silty currents, 138, 150 

 Turkey, recent earthquake in, 15 

 Typhoons in relation to "drowned" 



atolls, 75 



Li nderflow, silty. See Density currents 



United States, continental terraces off, 8, 

 116, 136 



United States Coast and Geodedc Sur- 

 vey, 115, 155 



United States Soil Conservation Service. 

 See Figure 74 



Upheaval 



in Canada after removal of ice load, 



44 



future, in Fennoscandia, 41 



in Fennoscandia, 35, 37, 38 



of mountain chains, delayed, 94 

 Uplift hypothesis to explain submarine 



valleys, 128 

 Underflows. See Density currents 

 Upolu Island, 18, 51 

 Uvea Island, a test of prolonged crustal 



stability, 66 



V alley systems of continental slope, 



in ff 



origin of, 127 ff 



pattern of, 139 

 Van Bemmelen, R. W., 83 

 Vancouver, British Columbia, 136 

 Veatch, A. C, investigator of submarine 



valleys, 116, 120, 122, 140, 166 

 Velocity of bottom density current, 



formula for, 150 

 Vening Meinesz, F. A., investigator of 



sub-oceanic structures, 28, 63, 77, 80, 



85, 90, 95, 98, 165 



