sentences:  The first global compilation of arc volcanoes using recent bathymetric data estimated that arcs that are at least partially submarine have a population of almost 700 volcanoes, of which at least 200 are submerged .estimated that intraoceanic arcs combined may contribute hydrothermal emissions equal to ~10% of that from the global mid-ocean ridge system.Guam in the southern IBM arc system is where Magellan first landed after his epic crossing of the Pacific Ocean in 1521.