VIII. Petrographical notes on the products of the eruptions of May, 1902, at the Soufrière in St. Vincent

Abstract

The rocks collected during our visit to the West Indies, in 1902, included specimens of the ashes, ejected blocks, &c., cast out by the eruptions of May, and of such lavas, belonging to previous eruptions of the Soufrière and the extinct volcanoes of the south part of the island, as were in good preservation and easily accessible from our line of route. We are also indebted to Mr. Macdonald, Mr. Darrell, and other inhabitants of St. Vincent, and to Sir Daniel Morris and the officers of the Imperial Agricultural Department for the West Indies acting under him (more particularly to Mr. Henry Powell, Curator of the Botanic Station, St. Vincent), for specimens sent us after our departure for England. Professor Lacroix has very kindly furnished us with specimens of the older rocks of St. Vincent, which he collected during his visit, and of an ejected block containing cordierite, which he found on the edge of the crater in January, 1903. The Ejecta of the Eruptions of May, 1902. Among the materials ejected during May, 1902, there were not only ashes and sand, with volcanic bombs which were derived from the active magma within the crater, but also large quantities of the older rocks of the mountain which had been torn from the walls of the crater and were mingled with the new ashes. The difficulties of collecting from the deposits of hot sand laid down by the avalanche were considerable, as the principal stream sections of the new materials were too hot and too unstable to be approached. Fragments lying on the surface of the avalanche evidently belonged to the most recent stages of the volcanic activity. The deeper parts of the new deposit were usually inaccessible, but where the secondary steam explosions had built small cones on the rivulets it was easy to collect blocks that had been projected from the interior of the beds of hot ash. These form the major part of the ejected blocks of 1902 contained in our collections.