Suiyo Seamount
Encyclopedia
Suiyo Seamount is a seamount
(submarine volcano
) off the eastern coast of Japan, directly south of Torishima
and Sofugan volcano
at the southern tip of the Izu Islands
. The volcano is one of the Shichiyo Seamounts, a small group of submarine volcanoes named after different days of the week ("Suiyo" means "Wednesday" in Japanese
).
Suiyo consists of a basalt
ic to dacitic submarine caldera
and lava dome
, and rises about 1400 m (4,593.2 ft) from its base on the sea floor to within 1418 m (4,652 ft) of the surface. Suiyo has a prominent summit caldera, 1.5 km (0.93205910497471 mi) wide and 500 m (1,640.4 ft) deep.
The volcano's excised (weathered) structure suggests that it is of older age then some of the other volcanoes in the group. Suiyo is covered by a thick sediment
cap, a feature that collects over a long span of inactivity, and fault patterns and valleys have been observed on its flanks.
Suiyo Seamount is associated with a magnetic anomaly
: ocean-floor surveys of it and the surrounding area found that a large negative rock body existed to the east of the seamount, while positive bodies existed to the northwest and south. The reasons for this complex anomaly, which also exists in several other nearby seamounts, is unknown, but is suggested to be the result of interactions between different magnetic field
s of different ages.
A burst of hydrothermal activity
was observed in July of 1991, raising water temperatures at the vent to 290 °C (554 °F); following the event, the volcano, until then thought extinct, was reclassified as active by the Japan Meteorological Agency
. A bathymetric survey of the volcano found sulfur-oxidizing microbes to be predominant, and concluded that Suiyo Seamount was a natural "incubator" for this bacterial type.
Seamount
A seamount is a mountain rising from the ocean seafloor that does not reach to the water's surface , and thus is not an island. These are typically formed from extinct volcanoes, that rise abruptly and are usually found rising from a seafloor of depth. They are defined by oceanographers as...
(submarine volcano
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...
) off the eastern coast of Japan, directly south of Torishima
Torishima (Izu Islands)
, literally meaning "Bird Island", is an uninhabited volcanic island at the south end of the Izu Islands in the Pacific Ocean, administered by Japan.-Geography:...
and Sofugan volcano
Lot's Wife (crag)
is a volcanic, deserted island located in the Philippine Sea approximately off the coast of Tokyo, in the southernmost tip of the Izu archipelago, Japan.-Geography:...
at the southern tip of the Izu Islands
Izu Islands
The are a group of volcanic islands stretching south and east from the Izu Peninsula of Honshū, Japan. Administratively, they form two towns and six villages; all part of Tokyo. The largest is Izu Ōshima, usually called simply Ōshima....
. The volcano is one of the Shichiyo Seamounts, a small group of submarine volcanoes named after different days of the week ("Suiyo" means "Wednesday" in Japanese
Japanese language
is a language spoken by over 130 million people in Japan and in Japanese emigrant communities. It is a member of the Japonic language family, which has a number of proposed relationships with other languages, none of which has gained wide acceptance among historical linguists .Japanese is an...
).
Suiyo consists of a basalt
Basalt
Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...
ic to dacitic submarine caldera
Caldera
A caldera is a cauldron-like volcanic feature usually formed by the collapse of land following a volcanic eruption, such as the one at Yellowstone National Park in the US. They are sometimes confused with volcanic craters...
and lava dome
Lava dome
|250px|thumb|right|Image of the [[rhyolitic]] lava dome of [[Chaitén Volcano]] during its 2008–2009 eruption.In volcanology, a lava dome is a roughly circular mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano...
, and rises about 1400 m (4,593.2 ft) from its base on the sea floor to within 1418 m (4,652 ft) of the surface. Suiyo has a prominent summit caldera, 1.5 km (0.93205910497471 mi) wide and 500 m (1,640.4 ft) deep.
The volcano's excised (weathered) structure suggests that it is of older age then some of the other volcanoes in the group. Suiyo is covered by a thick sediment
Sediment
Sediment is naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself....
cap, a feature that collects over a long span of inactivity, and fault patterns and valleys have been observed on its flanks.
Suiyo Seamount is associated with a magnetic anomaly
Magnetic anomaly
In geophysics, a magnetic anomaly is a local variation in the Earth's magnetic field resulting from variations in the chemistry or magnetism of the rocks. Mapping of variation over an area is valuable in detecting structures obscured by overlying material...
: ocean-floor surveys of it and the surrounding area found that a large negative rock body existed to the east of the seamount, while positive bodies existed to the northwest and south. The reasons for this complex anomaly, which also exists in several other nearby seamounts, is unknown, but is suggested to be the result of interactions between different magnetic field
Magnetic field
A magnetic field is a mathematical description of the magnetic influence of electric currents and magnetic materials. The magnetic field at any given point is specified by both a direction and a magnitude ; as such it is a vector field.Technically, a magnetic field is a pseudo vector;...
s of different ages.
A burst of hydrothermal activity
Hydrothermal vent
A hydrothermal vent is a fissure in a planet's surface from which geothermally heated water issues. Hydrothermal vents are commonly found near volcanically active places, areas where tectonic plates are moving apart, ocean basins, and hotspots. Hydrothermal vents exist because the earth is both...
was observed in July of 1991, raising water temperatures at the vent to 290 °C (554 °F); following the event, the volcano, until then thought extinct, was reclassified as active by the Japan Meteorological Agency
Japan Meteorological Agency
The or JMA, is the Japanese government's weather service. Charged with gathering and reporting weather data and forecasts in Japan, it is a semi-autonomous part of the Ministry of Land, Infrastructure and Transport...
. A bathymetric survey of the volcano found sulfur-oxidizing microbes to be predominant, and concluded that Suiyo Seamount was a natural "incubator" for this bacterial type.