South Chamorro Seamount
Encyclopedia
South Chamorro Seamount is a large serpentinite
mud volcano
and seamount
located in the Izu-Bonin-Mariana Arc
, one of 16 such volcanoes in the arc. These seamounts are at their largest 50 km (31 mi) in diameter and 2.4 km (1 mi) in height. Studies of the seamount include dives by the submersible
dives (DSV Shinkai
, 1993 and 1997), drilling (Ocean Drilling Program
, 2001), and ROV
dives (2003, 2009).
The seamount and its nearby peers were created by the movement of crushed rock, resulting from plate movement
, upwards through fissure
s in the Mariana Plate
. South Chamorro is the farthest of the mud volcanoes from the trench, at a distance of 85 km (53 mi), resulting in high-temperature flows rich in sulfate
and methane
. The seamount suffered a major flank collapse
on its southeastern side, over which the present summit was probably formed. The summit supports an ecosystem of mussel
s, gastropods, tubeworms, and others, suggesting that it is an active seeping
region.
of the Pacific Plate
below the Mariana Plate
; fault lines in the Mariana Plate provide a gateway for churned up rock and fluid from the grinding process up to the ocean surface. Reactions with the overlying mantle produce serpentinite
, hydrogen gas, and other alkaline substances.
South Chamorro Seamount was first recognized as a mud volcano is 1977, on the basis of sonar data
, and confirmed as such in 1981 by the collection of serpentine and schist
. is one of the farthest volcanoes from the trench, 85 km (53 mi) away, where the plate rides approximately 25 km (16 mi) underneath. Because of its distance from the trench, its eruptive fluids are hotter (> 350 °C (662 °F)), less alkalic, and with more calcium
. Its flows have a pH
of 12.2 (highly basic
) and are sulfate
and methane
rich.
Serpentine mud volcanoes are currently limited to the Izu-Bonin-Mariana arc; however, there is evidence of the geological remnants of similar volcanics globally, throughout Earth's history.
s of South Chamorro Seamount show a major southeastern sector edifice collapse, with debris flows of serpentine material (dredged in 1981 and observed by submersible
s in 1995) that blankets the slope of the trench from summit to axis. The true summit of the volcano sits above this collapse; its formation was likely tied to the collapse. Submarine observation of the summit show that the summit knoll is broken up into slabs of serpentine mud, with meter-deep fissure
s arranged in a crosscutting orientation.
s, gastropods, tubeworms, and galatheid crab
s. A borehole observatory on the summit produced 20,000 litters of microbally-altered fluid per day for study. These organisms are supported by low-temperature springs from the fissures surrounding the summit zone. The mussels are probably of the genus
Bathymodiolus
, which require a high concentration of methane
in their food source. The fluid composition and the biological community suggests that the summit region is an active cold seep
region.
Serpentinite
Serpentinite is a rock composed of one or more serpentine group minerals. Minerals in this group are formed by serpentinization, a hydration and metamorphic transformation of ultramafic rock from the Earth's mantle...
mud volcano
Mud volcano
The term mud volcano or mud dome are used to refer to formations created by geo-excreted liquids and gases, although there are several different processes which may cause such activity. Hot water mixes with mud and surface deposits. Mud volcanoes are associated with subduction zones and about 700...
and seamount
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...
located in the Izu-Bonin-Mariana Arc
Izu-Bonin-Mariana Arc
The Izu-Bonin-Mariana arc system is an outstanding example of a plate tectonic convergent boundary. IBM extends over 2800 km south from Tokyo, Japan, to beyond Guam, and includes the Izu Islands, Bonin Islands, and Mariana Islands; much more of the IBM arc system is submerged below sealevel...
, one of 16 such volcanoes in the arc. These seamounts are at their largest 50 km (31 mi) in diameter and 2.4 km (1 mi) in height. Studies of the seamount include dives by the submersible
Submersible
A submersible is a small vehicle designed to operate underwater. The term submersible is often used to differentiate from other underwater vehicles known as submarines, in that a submarine is a fully autonomous craft, capable of renewing its own power and breathing air, whereas a submersible is...
dives (DSV Shinkai
DSV Shinkai
The Shinkai 6500 is a manned research submersible that can dive up to a depth of 6,500 m. It was completed in 1990 and has the greatest depth range of any manned research vehicle in the world. The only manned expedition to have gone deeper was the dive of the Trieste bathyscaphe in 1960. However,...
, 1993 and 1997), drilling (Ocean Drilling Program
Ocean Drilling Program
The Ocean Drilling Program was an international cooperative effort to explore and study the composition and structure of the Earth's ocean basins. ODP, which began in 1985, was the direct successor to the highly successful Deep Sea Drilling Project initiated in 1968 by the United States...
, 2001), and ROV
Remotely operated vehicle
A remotely operated vehicle is a tethered underwater vehicle. They are common in deepwater industries such as offshore hydrocarbon extraction. An ROV may sometimes be called a remotely operated underwater vehicle to distinguish it from remote control vehicles operating on land or in the air. ROVs...
dives (2003, 2009).
The seamount and its nearby peers were created by the movement of crushed rock, resulting from plate movement
Plate tectonics
Plate tectonics is a scientific theory that describes the large scale motions of Earth's lithosphere...
, upwards through fissure
Fissure
In anatomy, a fissure is a groove, natural division, deep furrow, elongated cleft, or tear in various parts of the body.-Brain:...
s in the Mariana Plate
Mariana Plate
The Mariana Plate is a small tectonic plate located west of the Mariana Trench and forms the basement of the Mariana Islands. It is separated from the Philippine Sea Plate by a long divergent boundary with numerous transform fault offsets. The boundary between the Mariana and the Pacific Plate to...
. South Chamorro is the farthest of the mud volcanoes from the trench, at a distance of 85 km (53 mi), resulting in high-temperature flows rich in sulfate
Sulfate
In inorganic chemistry, a sulfate is a salt of sulfuric acid.-Chemical properties:...
and methane
Methane
Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...
. The seamount suffered a major flank collapse
Landslide
A landslide or landslip is a geological phenomenon which includes a wide range of ground movement, such as rockfalls, deep failure of slopes and shallow debris flows, which can occur in offshore, coastal and onshore environments...
on its southeastern side, over which the present summit was probably formed. The summit supports an ecosystem of mussel
Mussel
The common name mussel is used for members of several families of clams or bivalvia mollusca, from saltwater and freshwater habitats. These groups have in common a shell whose outline is elongated and asymmetrical compared with other edible clams, which are often more or less rounded or oval.The...
s, gastropods, tubeworms, and others, suggesting that it is an active seeping
Cold seep
A cold seep is an area of the ocean floor where hydrogen sulfide, methane and other hydrocarbon-rich fluid seepage occurs, often in the form of a brine pool...
region.
Origin and geochemistry
South Chamorro Seamount and the other mud volcanoes formed as a result of the subductionSubduction
In geology, subduction is the process that takes place at convergent boundaries by which one tectonic plate moves under another tectonic plate, sinking into the Earth's mantle, as the plates converge. These 3D regions of mantle downwellings are known as "Subduction Zones"...
of the Pacific Plate
Pacific Plate
The Pacific Plate is an oceanic tectonic plate that lies beneath the Pacific Ocean. At 103 million square kilometres, it is the largest tectonic plate....
below the Mariana Plate
Mariana Plate
The Mariana Plate is a small tectonic plate located west of the Mariana Trench and forms the basement of the Mariana Islands. It is separated from the Philippine Sea Plate by a long divergent boundary with numerous transform fault offsets. The boundary between the Mariana and the Pacific Plate to...
; fault lines in the Mariana Plate provide a gateway for churned up rock and fluid from the grinding process up to the ocean surface. Reactions with the overlying mantle produce serpentinite
Serpentinite
Serpentinite is a rock composed of one or more serpentine group minerals. Minerals in this group are formed by serpentinization, a hydration and metamorphic transformation of ultramafic rock from the Earth's mantle...
, hydrogen gas, and other alkaline substances.
South Chamorro Seamount was first recognized as a mud volcano is 1977, on the basis of sonar data
Sonar
Sonar is a technique that uses sound propagation to navigate, communicate with or detect other vessels...
, and confirmed as such in 1981 by the collection of serpentine and schist
Schist
The schists constitute a group of medium-grade metamorphic rocks, chiefly notable for the preponderance of lamellar minerals such as micas, chlorite, talc, hornblende, graphite, and others. Quartz often occurs in drawn-out grains to such an extent that a particular form called quartz schist is...
. is one of the farthest volcanoes from the trench, 85 km (53 mi) away, where the plate rides approximately 25 km (16 mi) underneath. Because of its distance from the trench, its eruptive fluids are hotter (> 350 °C (662 °F)), less alkalic, and with more calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
. Its flows have a pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...
of 12.2 (highly basic
Base (chemistry)
For the term in genetics, see base A base in chemistry is a substance that can accept hydrogen ions or more generally, donate electron pairs. A soluble base is referred to as an alkali if it contains and releases hydroxide ions quantitatively...
) and are sulfate
Sulfate
In inorganic chemistry, a sulfate is a salt of sulfuric acid.-Chemical properties:...
and methane
Methane
Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...
rich.
Serpentine mud volcanoes are currently limited to the Izu-Bonin-Mariana arc; however, there is evidence of the geological remnants of similar volcanics globally, throughout Earth's history.
Structure
Side-scan surveySide-scan sonar
Side-scan sonar is a category of sonar system that is used to efficiently create an image of large areas of the sea floor...
s of South Chamorro Seamount show a major southeastern sector edifice collapse, with debris flows of serpentine material (dredged in 1981 and observed by submersible
Submersible
A submersible is a small vehicle designed to operate underwater. The term submersible is often used to differentiate from other underwater vehicles known as submarines, in that a submarine is a fully autonomous craft, capable of renewing its own power and breathing air, whereas a submersible is...
s in 1995) that blankets the slope of the trench from summit to axis. The true summit of the volcano sits above this collapse; its formation was likely tied to the collapse. Submarine observation of the summit show that the summit knoll is broken up into slabs of serpentine mud, with meter-deep fissure
Fissure
In anatomy, a fissure is a groove, natural division, deep furrow, elongated cleft, or tear in various parts of the body.-Brain:...
s arranged in a crosscutting orientation.
Ecology
South Chamorro Seamount is host to a variety of fauna, including musselMussel
The common name mussel is used for members of several families of clams or bivalvia mollusca, from saltwater and freshwater habitats. These groups have in common a shell whose outline is elongated and asymmetrical compared with other edible clams, which are often more or less rounded or oval.The...
s, gastropods, tubeworms, and galatheid crab
Squat lobster
Squat lobsters are decapod crustaceans of the families Galatheidae, Chirostylidae and Kiwaidae, including the common genera Galathea and Munida. They are not lobsters at all, but are more closely related to porcelain crabs, hermit crabs and then, more distantly, true crabs...
s. A borehole observatory on the summit produced 20,000 litters of microbally-altered fluid per day for study. These organisms are supported by low-temperature springs from the fissures surrounding the summit zone. The mussels are probably of the genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Bathymodiolus
Bathymodiolus
Bathymodiolus is a genus of deep-sea chemosynthetic mussels.-Species:Modern species within the genus Bathymodiolus include:* Bathymodiolus childressi Gustafson, Lutz, Turner & Vrijenhoek, 1998* Bathymodiolus japonicus Hashimoto & Okutani, 1994...
, which require a high concentration of methane
Methane
Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...
in their food source. The fluid composition and the biological community suggests that the summit region is an active cold seep
Cold seep
A cold seep is an area of the ocean floor where hydrogen sulfide, methane and other hydrocarbon-rich fluid seepage occurs, often in the form of a brine pool...
region.
See also
- Graveyard SeamountsGraveyard SeamountsThe Graveyard Seamounts are a series of 28 small seamounts and ediffices located on the Chatham Rise, east of New Zealand. They cover about , and stand out from the surrounding oceanic plateau that measures several hundred kilometers...
- Jasper SeamountJasper SeamountJasper Seamount is a seamount located in the Fieberling-Guadalupe seamount track, west of Baja California, Mexico. Jasper is the site of detailed geophysical geological and geochemical studies which suggest that many seamounts, big and small, follow the same pattern of growth and death that was...
- Mud volcanoMud volcanoThe term mud volcano or mud dome are used to refer to formations created by geo-excreted liquids and gases, although there are several different processes which may cause such activity. Hot water mixes with mud and surface deposits. Mud volcanoes are associated with subduction zones and about 700...
- Muirfield SeamountMuirfield SeamountThe Muirfield Seamount is a submarine mountain located in the Indian Ocean approximately 130 kilometres southwest of the Cocos Islands. The Cocos Islands are an Australian territory, and therefore the Muirfield Seamount is within in Australia's Exclusive Economic Zone...
- Sedlo SeamountSedlo SeamountSedlo Seamount is an isolated seamount and underwater volcano located in the Northeast Atlantic, northeast of Graciosa Island. It has an elongate structure, roughly . The summit is flat with three peaks. Sedlo Seamount sits on the ocean floor deep, and rises to within of the surface...