West Mata

Outbreak of West Mata in May 2009


West Mata submarine volcano is located about 200 km southwest of Samoa in the Pacific.

The summit crater is located 1000 m below the sea surface. The volcano is currently one of the deepest known submarine volcanoes, and the first in which it was possible to film an eruption.

Geological classification

Exact Location

West Mata is located in the west of the northern end of the Tonga Ridge, where the Tonga Trench makes a sharp bend to the west. It is located in the northeastern Lau Valley about 35 km east of the Lau -strain zone and 70 km north-east of its constantly erupting volcano.

First news of an outbreak

In November 2008 it was announced that presumably would find was a submarine eruption at the site.


The research vessel Thompson explored the area between November 2008 and May 2009. In November 2008, the researchers saw an eruption column over West Mata, who pointed to an active lava flow or pyroclastic flow.

On closer examination it turned out that the eruption column containing glass fragments, which were rich in sulfur and iron. Laboratory tests proved a composition of the ejecta from Boninit, an olivine - bronzite - andesite without feldspar, a mixture that was never before found in an active, but only in extinct volcanoes.

On May 6 and 7 In 2009, you should allow a submersible robot called Jason 2 ROV to observe eruptions at two outbreak sites of the elongated West Mata summit in more detail. The outbreak sites were named Prometheus ( on or near the summit ) and Hades (some southwesterly ).

The eruption site called Hades produced a mixed eruption over the two days. At one end of the eruption column could be observed small explosions at a 5 m long column at a depth of 1208 m, while at the other end of pillow lava welled out. The following night, the activity increased and the volcano threw glowing bubbles one meter far from the eruptive fissure.


Recordings of the ROV were published by the National Oceanic and Atmospheric Administration in December 2009 in a video.