Abstract
The Philippine Island Arc has a large number of volcanoes with diverse morphologies, making it an ideal location to study the factors controlling the morphology and spatial distribution of island arc volcanoes. We have identified 731 volcanic edifices using the SRTM 30 m digital elevation model, and computed their quantitative morphology using the MORVOLC algorithm. Hierarchical classification by principal component (PC) analysis distinguishes four volcano types: small flat cones, small steep cones, large cones, and massifs, with mean volumes of 0.2 km3 (<6.2 km3),="" 0.4="" km3=""><9 km3),="" 29="" km3="" (0.15–178="" km3),="" 267="" km3="" (76–675="" km3),="" mean="" heights="" of="" 125 m="" (16–721 m),="" 260 m="" (53–971 m),="" 842 m="" (59–2313 m),="" 1533 m="" (1012–2175 m),="" and="" mean="" slopes="" of="" 13°="" (3–21°),="" 22°="" (14–37°),="" 15°="" (3–28°),="" 15°="" (11–22°),="" respectively.="" this="" classification="" is="" based="" mainly="" on="" their="" size="" and="" irregularity="" (pc1)="" and="" steepness="" (mean="" slope="" and="" height/basal="" width="" ratio;="" pc2),="" and="" to="" a="" lesser="" extent="" on="" the="" size="" of="" the="" summit="" region="" and="" edifice="" truncation="" (pc3)="" and="" edifice="" elongation="" (pc4).="" these="" morphological="" volcano="" classes="" represent="" stages="" along="" an="" evolutionary="" trend.="" the="" small="" flat="" cones="" are="" mostly="" monogenetic,="" whereas="" the="" small="" steep="" cone="" class="" represents="" an="" early="" growth="" stage.="" some="" can="" develop="" into="" large="" polygenetic="" cones="" while="" a="" few="" can="" further="" grow="" laterally="" into="" massifs,="" both="" of="" which="" are="" preferentially="" found="" on="" thickened="" crust.="" there="" is="" a="" trend="" towards="" more="" silicic="" compositions="" from="" small="" to="" large="" cones,="" perhaps="" due="" to="" larger="" edifice="" loads="" preventing="" mafic="" dykes="" from="" reaching="" the="" surface.="" the="" distribution="" and="" alignment="" of="" the="" edifices="" within="" volcanic="" fields="" seems="" to="" be="" influenced="" by="" both="" regional="" and="" local="" stress="" fields="" and="" pre-existing="">
Keywords
Cluster analysis, Philippine volcanoes, Principal component analysis, Volcano growth, Volcano morphometry, Volcano spatial distribution