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 Trachyte and Basalt from Kodiak Seamount and the Adjacent Aleutian Trench, Alaska
Blocky fragments of aegirine-augite trachyte (with accompanying icerafted gravels.) were recovered from the upper slopes of Kodiak Seamount in several dredge hauls. An alkali basalt pillow segment was also dredged from a moatlike depression, at a depth of 5000 meters, near the west base of the seamount. These retrievals confirm the volcanic origin of Kodiak Seamount and further support the view of Engel, Engel, and Havens that the higher elevations of seamounts are composed of alkali basalts or related variants.
Chronology of the Explosive Eruptions of Kilauea
THE EXPLOSIVE ERUPTIONS of Kilauea, both prehistoric and historic, have been much discussed in the literature on Hawaiian volcanoes. Some early general observations attributed all of the surface ash deposits to the known explosive eruption of 1790 (Dana, 1891: 42-45; Jaggar,I921: 114-118); others recognized evidence of several different prehistoric explosions (Hitchcock, 1911: 166-169; Sidney Powers, 1916). Later studies, with better exposures in artificial cuts on the windward rim of the crater, demonstrated a number of long intervals of quiet between several eruptions (Finch, 1925; . Stone, 1926) . This paper adds another, still more detailed, chapter to the accumulated knowledge, but much remains to be learned and recorded before complete understanding of the explosive phases of the volcano is attained. Many of the thoughts expressed herein are the result of discussion and exchange of ideas in the field with many coworkers, whose contributions are gratefully accepted and acknowledged. T. A. Jaggar, R. H. Finch, E. G. Wingate, A. E. Jones, all formerly with the Hawaiian Volcano Observatory; J. E. Doerr, Jr ., former naturalist, Hawaii National Park; H. S. Palmer of the University of Hawaii; C. K Wentworth of the Honolulu Board of Water Supply; and G. A. Macdonald of the United States Geological Survey have all contributed to the accumulation and consideration of material which is presented in this paper. The erratic original deposition of the pyroclastics of Kilauea, controlled by combinations of atmospheric elements and directed explo-