A volcanic cruise through the Mariana Islands: Part 2

Our tour of the Marianas begins SW of Guam. In this area the volcanoes are submerged and make up a region known as the Southern Seamount Province. Our first stop is Tracey Seamount, which lies 30 km west of Guam. Tracey is a ~2 km tall cone and volume of ~45 km^3 It is one of the smaller volcanoes in the Mariana arc; Pagan, contains about 2200 km^3 of material (Bloomer et al., 1989). It has a sector collapse on its western flank and resembles a submarine Mt. St. Helens. It was investigated by the ROV Hyper-Dolphin from the R/V Natsushima in Feb. 2009, which revealed that the cone is map up of alternating pyroclastics and dacite built on a basaltic-andesite base. A dome of dacite has formed in the collapse area. It is still considered active and that along with its proximity to Guam and its history of sector collapse suggest an underappreciated risk to the island.