Northwest Rota

NW Rota-1 is a seamount in the Mariana Islands, northwest of Rota, which was discovered through its hydrothermal activity in 2003. The volcano has been observed to be erupting underwater, the first time that submarine explosive eruptions have been directly witnessed.

The summit of the seamount lies at 517 m (1,696 ft) below sea level, with a ridge capping off the seamount. It has several craters, the most active of which is located south of the summit ridge and is called "Brimstone Pit". Eruptions have been recorded in 2008–2010 and took the form of Strombolian eruptions with the emission of lava and large amounts of tephra. The erupted material is unstable and forms sediment flows and landslides; one large landslide occurred on 14 August 2009 and stripped part of the southern flank of NW Rota-1. Such landslides generate ash plumes underwater and are similar to large landslides at other active submarine volcanoes.

The activity gives rise to intense hydrothermal plumes, which contain droplets of molten sulfur and bubbles of carbon dioxide, among other compounds. It is estimated that NW Rota-1 releases 400,000 ± 100,000 tonne/year of carbon dioxide. The hydrothermal activity nourishes microbial mats and these in turn many animals, although the unstable environment from the frequent eruptions limits animal diversity.