Subaqueous sulphur lake in Volcan Poas

Abstract

GREENISH amorphous sulphur particles are present at all levels immediately around the crater of Volcan Poas. The eruptive plumes of the mild submarine volcanism which characterises this volcano, are charged with these particles. We suggest here that they are strong evidence that a lake of molten sulphur exists, or is formed temporarily before an eruption, below the existing lake of water in the crater. We have collected many samples of greenish amorphous sulphur, with various quantities of admixed ash from regions all around the crater, noting some concentrations in the east–west prevailing wind directions. Figure 1 shows sulphur specimens and their morphology; Fig. 2 gives a profile of the crater; Fig. 3 shows approximate outlines of areas in which sulphur samples are found. Table 1 gives approximate analyses of representative samples.