From Wood and Kienle (1990): "Chagulak is a small
stratovolcano separated from Amukta by ~7 km of ocean, but the two coalesce at depth. Chagulak is unstudied; the only geologic information available is a single chemical analysis. A low-potassium, high-alumina basaltic andesite (51% SiO2, 0.59% K2O) was recovered from the north-northwest shore of the island, but the sample's geologic setting is unknown."