Basalts Dredged from the Northeastern Pacific Ocean
Volcanic rocks dredged from seamounts, fault ridges, and other major geological features of the northeast Pacific Ocean include a wide variety of basalts. Most of these are vesicular, porphyritic types with near analogues in the Hawaiian and other oceanic islands. In addition, aluminous basalts and diabasic theoleiites impoverished in potassium also occur. There is no simple correlation of composition, degree of oxidation, vesiculation, or hydration of these basalts with texture, or depth of dredge site. Most samples appear to have been extruded at much shallower depths than those now pertaining at the dredge site. The distribution of these basalts suggests that the andesite line coincides with or lies on the continent side of the foot of the continental slope.
Dredged Basalt from Giacomini Seamount
DURING the cruise in July 1965 of the RV Acona of the University of Alaska Institute of Marine Science, two angular blocks of basalt (15×12×5 cm3 and 20×15×9 cm3) were dredged from the summit area of Giacomini Seamount (56° 24′ N, 146° 34′ W), at a depth of 790 m (Fig. 1). Several hundred igneous, metamorphic and sedimentary pebbles, cobbles and boulders were also recovered in the dredge haul; they showed a wide range of rounding and a very thin coating of manganese oxide, and were very similar to those recovered from the summit areas of Gilbert, Miller, Pratt and Ga-3 Seamounts in the Gulf of Alaska Seamount Province, as previously reported by Menard1 and others. Menard concluded that these gravels were ice-rafted glacial drift, an interpretation which is strongly supported by the presence of faceted and striated rocks among the Giacomini erratics.
Crustal structure and surface-wave dispersion. Part II. Solomon Islands earthquake of July 29, 1950
Rayleigh waves from the Solomon Islands earthquake of July 29, 1950, recorded at Honolulu, 
Berkeley, Tucson, and Palisades are analyzed. Both the direct waves and those propagated 
through the Antipodes were observed for all stations except Honolulu. Application of a correction 
for land travel results in a dispersion curve for the oceanic portion of the path. It is found 
that the observed dispersion could be accounted for by propagation through a layer of water 
5.57 km. thick overlying simatic rocks having shear velocity 4.56 km/sec. and density 3.0 gm/cc. 
Basement structure in the Pacific, Indian, South Atlantic, and North Atlantic oceans is identical 
within the limits of accuracy of the method. 
The sinusoidal nature and duration of the coda is explained by the effect of the oceans on the 
propagation of Rayleigh waves. 
The results are compatible with seismic refraction measurements in the Atlantic and Pacific 
oceans.