According to a news article from 20 April, scientists investigating NW Rota-1 during the previous two weeks observed the volcano erupting about 520 m below the ocean's surface. Measurements indicated that the volcano had grown about 40 m since 2006. One scientist observed billowing yellow and white sulfur clouds, carbon dioxide bubbles streaming out of the vent, and "ash and pebble-sized rocks raining out of the plume."

Geological Summary. A submarine volcano detected during a 2003 NOAA bathymetric survey of the Mariana Island arc was found to be hydrothermally active and named NW Rota-1. The basaltic to basaltic-andesite seamount rises to within 517 m of the ocean surface SW of Esmeralda Bank, 64 km NW of Rota Island and ~100 km N of Guam. When Northwest Rota-1 was revisited in 2004, a minor submarine eruption from a vent named Brimstone Pit on the upper south flank about 40 m below the summit intermittently ejected a plume several hundred meters high containing ash, rock particles, and molten sulfur droplets that adhered to the surface of the remotely operated submersible vehicle. The active vent was funnel-shaped, about 20 m wide and 12 m deep. Prominent structural lineaments about a kilometer apart cut across the summit of the edifice and down the NE and SW flanks.

Source: GuamPDN - Pacific Daily News