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.
Drowned ancient islands of the Pacific Basin
A large number of curious, flat-topped peaks have been discovered scattered over millions of square miles in the Pacific Basin. These peaks are roughly oval In plan and their slopes suggest volcanic cones. The remarkable feature about them is that they are truncated by a level surface which now stands approximately 750 fathoms (4500 feet) below sea level.
Contributions to the petrography of the Sandwich Islands
Dana describes specimens of lava, including lava stalactites, from Mauna Loa and from Kilauea, collected by J.D. Dana and E.S. Baker. The lavas of Mokuaweoweo and Kilauea are found to be strikingly similar. Samples from Mokuaweoweo include clinkstone-like basalt, chrysolitic basalt, lavas with minute feldspar and augite crystals in their cavities, and others. He describes elongated (skeletal) olivine crystals and dendritic growths of augite, illustrated by excellent drawings. Glass is found to contain both microlites and crystallites. The lava stalactites, also well-photographed, are thought to have been formed by a process of "aqueo-fusion" by highly heated water vapor. Dana also describes 1790 ejecta, including one block with apatite-bearing glass in vesicles, and lava from Haleakala on Maui and from Oahu.