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 km3 It is one of the smaller volcanoes in the Mariana arc; Pagan, contains about 2200 km3 of material (Bloomer et al., 1989). It has a sector collapse on its western flank and resembles a submarine Mt. St. Helens.