Mount Umsini ("Oemsini") is internationally listed as an active volcano in the Bird's Head Irian Jaya (New Guinea)/ The mountain occurs at the north end of the Arfak Mountains, a range consisting of tilted and presumably folded early Tertiary turbidite sequences and volcanoclastic rocks that were intruded by Early Oligocene gabbroic rocks. The morphology is characterized by NNW-striking, long, …