West Mata
Encyclopedia
West Mata is a submarine volcano
located 200 kilometres (124.3 mi) southwest of the Samoas
. The volcano's peak lies 1,100 meters underwater. The volcano is currently the deepest erupting submarine volcano in the ocean, and the first to ever be filmed erupting. Scientists have made attempts to film an erupting submarine volcano for 25 years.
makes a sharp turn to the west. It is in the NE Lau Basin
about 35 km east of the Lau spreading center and about 70 km northeast of the currently erupting NE Lau spreading center. The Research Vessel Thompson surveyed the area during November 2008 and May 2009. In November 2008, the researchers detected a plume of material over West Mata which indicated likely erupting lava
flows and/or pyroclastic materials. The sulfur and iron rich plume contained mineral and/or glass shards. The shard compositions indicated that the erupted material was boninite
(an olivine
-bronzite
andesite
with little or no feldspar
) which had never been observed from an active volcano.
On 6-7 May 2009, the Jason 2 ROV (remotely operated vehicle) was used to observe eruptions from two vents of the linear West Mata peak, Prometheus (at or near the summit) and Hades (slightly to the SW). The Hades vent was erupting both effusively and explosively at the same time on both days (6-7 May). Small bursts were occurring at one end of an erupting fissure ~ 5 m long at a depth of 1,208 m, while pillow lavas were being extruded from the other end. By the next night (7 May) the activity had become more vigorous, sometimes blowing glowing bubbles as much as a meter across from the fissure.
Submarine volcano
Submarine volcanoes are underwater fissures in the Earth's surface from which magma can erupt. They are estimated to account for 75% of annual magma output. The vast majority are located near areas of tectonic plate movement, known as ocean ridges...
located 200 kilometres (124.3 mi) southwest of the Samoas
Samoan Islands
The Samoan Islands or Samoa Islands is an archipelago covering in the central South Pacific, forming part of Polynesia and the wider region of Oceania...
. The volcano's peak lies 1,100 meters underwater. The volcano is currently the deepest erupting submarine volcano in the ocean, and the first to ever be filmed erupting. Scientists have made attempts to film an erupting submarine volcano for 25 years.
Geology
West Mata is located just west of the north end of the Tonga Ridge where the Tonga TrenchTonga Trench
The Tonga Trench is located in the South Pacific Ocean and is deep at its deepest point, known as the Horizon Deep.The Tonga Trench is a convergent plate boundary. The trench lies at the northern end of the Kermadec-Tonga Subduction Zone, an active subduction zone where the Pacific Plate is being...
makes a sharp turn to the west. It is in the NE Lau Basin
Lau Basin
The Lau Basin is an oceanic basin between the Pacific Plate and the Indo-Australian Plate by the Tonga Islands in the southwest Pacific. It is a relatively shallow basin between the islands and atoll feefs of the Lau Ridge/Lau Islands in the west and the Tonga Ridge/Tonga Islands and Tofua Arc in...
about 35 km east of the Lau spreading center and about 70 km northeast of the currently erupting NE Lau spreading center. The Research Vessel Thompson surveyed the area during November 2008 and May 2009. In November 2008, the researchers detected a plume of material over West Mata which indicated likely erupting lava
Lava
Lava refers both to molten rock expelled by a volcano during an eruption and the resulting rock after solidification and cooling. This molten rock is formed in the interior of some planets, including Earth, and some of their satellites. When first erupted from a volcanic vent, lava is a liquid at...
flows and/or pyroclastic materials. The sulfur and iron rich plume contained mineral and/or glass shards. The shard compositions indicated that the erupted material was boninite
Boninite
Boninite is a mafic extrusive rock high in both magnesium and silica, formed in fore-arc environments, typically during the early stages of subduction. The rock is named for its occurrence in the Izu-Bonin arc south of Japan...
(an olivine
Olivine
The mineral olivine is a magnesium iron silicate with the formula 2SiO4. It is a common mineral in the Earth's subsurface but weathers quickly on the surface....
-bronzite
Bronzite
Bronzite is a member of the orthopyroxene group of minerals, belonging with enstatite and hypersthene to the orthorhombic series of the group...
andesite
Andesite
Andesite is an extrusive igneous, volcanic rock, of intermediate composition, with aphanitic to porphyritic texture. In a general sense, it is the intermediate type between basalt and dacite. The mineral assemblage is typically dominated by plagioclase plus pyroxene and/or hornblende. Magnetite,...
with little or no feldspar
Feldspar
Feldspars are a group of rock-forming tectosilicate minerals which make up as much as 60% of the Earth's crust....
) which had never been observed from an active volcano.
On 6-7 May 2009, the Jason 2 ROV (remotely operated vehicle) was used to observe eruptions from two vents of the linear West Mata peak, Prometheus (at or near the summit) and Hades (slightly to the SW). The Hades vent was erupting both effusively and explosively at the same time on both days (6-7 May). Small bursts were occurring at one end of an erupting fissure ~ 5 m long at a depth of 1,208 m, while pillow lavas were being extruded from the other end. By the next night (7 May) the activity had become more vigorous, sometimes blowing glowing bubbles as much as a meter across from the fissure.