On the origin of the deep troughs of the oceanic depression; are any of volcanic origin?

Abstract

Dana presents a bathymetric map of the Pacific Ocean using recent charts of the Hydrographic Department of the United States and Great Britain. He summarizes facts bearing on a volcanic origin for depressions around the Hawaiian islands as follows (p. 196): "1. The Pacific soundings have made known the existence of two deep-sea depressions, if not a continuous trough, within forty miles of the Hawaiian Islands; one situated northeast of Oahu, or, north of Molokai, with a depth of 3023 fathoms, or 18,069 feet, and the other east of the east point of Hawaii, 2875 fathoms, or within 750 feet of 18,000 feet. Again, 450 miles northeast of Oahu, there is a trough in the ocean's bottom, over 800 miles long, which runs nearly parallel with the group and has a depth of 3000 to 3540 fathoms; and, as far south, another similar trough of probably greater length has afforded soundings of 3000 to 3100 fathoms. The depths about the more western part of the Hawaiian chain of islands have not yet been ascertained, and hence the limits of the deep areas are not known. Such depths, so close to a line of great volcanic mountains, the loftiest of the mountains not yet extinct, appear as if they might have resulted from a subsidence consequent on the volcanic action. "The subsidence might have taken place (1) either from underminings, which the amount of matter thrown out and now constituting the mountain chain, with its peaks of 20,000 to 30,000 feet above the sea-bottom, shows may be large; or (2) from the gravitational pressure in the earth's crust, about a volcanic region which speculation makes a source of the ascensive force and of the upward rising of the lavas, the subsiding crust following down the liquid surface beneath. In either case the mass of ejected material might be a measure more or less perfectly of the maximum amount of subsidence."