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Spotlight 2: Jasper Seamount
Jasper G. Konter,Hubert Staudigel,Jeffrey Gee
Oceanography , 2010,
Abstract: Jasper Seamount is a submarine volcano in the Fieberling-Guadalupe seamount trail, located off the coast of Baja California, Mexico. It rises from the 4000-m-deep seafloor to a summit depth of 700 m. Detailed geophysical, geochemical, and geological studies there provide an in-depth geological understanding of a seamount that approaches our knowledge of subaerial volcanoes. Active-source seismic experiments at Jasper Seamount resulted in the first seismic velocity models of an intraplate seamount. Marine gravity and magnetics surveys, combined with analyses of the physical properties, geochemistry, and geochronology of dredge samples, enabled scientists to develop a detailed model of its internal structure.
Spotlight 12: Sedlo Seamount
Ricardo S. Santos,Fernando Tempera,Gui Menezes,Filipe Porteiro
Oceanography , 2010,
Abstract: Sedlo is an isolated seamount in the Northeast Atlantic, 180 km northwest of Graciosa Island, within the Azores/Portuguese Exclusive Economic Zone, at 40°12.8’N, 26°15.8’ W. Sedlo is elongated, flat-topped, about 75 km by 30 km, and has three peaks. It rises steeply from a depth of about 3000 m, reaching 660 m at its shallowest part. The tablemount shape of this massif indicates that its top was once located at sea level and was abraded by oceanic swells before subsiding considerably.
Spotlight 1: Axial Seamount
William Chadwick,David Butterfield,Robert W. Embley,Verena Tunnicliffe
Oceanography , 2010,
Abstract: Axial Seamount is a hotspot volcano superimposed on the Juan de Fuca Ridge (JdFR) in the Northeast Pacific Ocean. Due to its robust magma supply, it rises ~ 800 m above the rest of JdFR and has a large elongate summit caldera with two rift zones that paral-lel and overlap with adjacent segments of the spreading center. Submersible dives at Axial in 1983–1984 discovered the first active black smoker vents in the Northeast Pacific. The New Millennium Observatory (NeMO; http://www.pmel.noaa.gov/vents/nemo/) was established at Axial in 1996 to study volcanic events and the perturbations they cause to hydrothermal and biological systems. As if on cue, Axial erupted in January 1998 and was the first seafloor eruption detected remotely and monitored by in situ instruments. In fact, one instrument was caught in a 1998 lava flow but later recovered with data intact, providing new insight into the emplacement of submarine lavas. Initially, research focused on mapping, sampling, and documenting the impact of the eruption on the hydrothermal vents and biological communities. The emphasis has gradually shifted to long-term geophysical, geochemical, and biological monitoring of the volcano in anticipation of its next eruption.
Spotlight 5: Great Meteor Seamount
Christian Mohn
Oceanography , 2010,
Abstract: Great Meteor Seamount is one of the largest seamounts in the Atlantic Ocean, rising from 4200-m depth at the seafloor to 270-m depth beneath the sea surface. Its elliptical plateau encompasses an area of 1500 km2, roughly matching the size of the Spanish island of Gran Canaria. There is a long tradition of multidisciplinary research at Great Meteor Seamount, dating back to 1967. It has become one of the best-studied seamounts globally, with research aimed at better understanding the connections between oceanic motion around seamount structures and biological distribution patterns. Meincke (1971) was the first to identify a circulation system in the form of an anticyclonic vortex trapped atop Great Meteor Seamount, with the potential to accumulate mesopelagic zooplankton, micronekton, and even fish species with weak swimming capabilities. Later studies revealed a more complex flow spectrum at the seamount, dominated by tidal and internal tidal motions and a high level of spatial and temporal variability. These findings, together with similar studies at other seamounts, indicate that seamounts play a role in ocean biology far beyond the classical view of particle retention inside stationary and closed circulation cells.
Spotlight 8: Vailulu’u Seamount
Anthony A.P. Koppers,Hubert Staudigel,Stanley R. Hart,Craig Young
Oceanography , 2010,
Abstract: Vailulu’u seamount is an active underwater volcano that marks the end of the Samoan hotspot trail. Vailulu’u has a simple conical morphology with a largely enclosed volcanic crater at relatively shallow water depths, ranging from 590 m (highest point on the crater rim) to 1050 m (crater floor). The crater hosts a 300-m-high central volcanic cone, Nafanua, that was formed between 2001 and 2004. Seismic activity at Vailulu’u included a series of globally recorded magnitude 4.1–4.9 earthquakes in 1973 and 1995, and substantial volcano-tectonic activity recorded over 45 days in 2000, with an average of four earthquakes per day and a maximum of 40 per day. Hypocenter locations are directly located below the major hydrothermal vent areas.
Spotlight 3: Lō`ihi Seamount
Hubert Staudigel,Craig L. Moyer,Michael O. Garcia,Alex Malahoff
Oceanography , 2010,
Abstract: Lō`ihi Seamount defines the volcanically active, leading edge in the Hawaiian hotspot chain. It is located on the submarine flank of Mauna Loa, 30 km south of the island of Hawai`i. Lō`ihi’s summit is at 975-m water depth (Pisces Peak), and the seamount has a pronounced southern rift that extends down to about 5000-m water depth (Figure 1). The summit displays three pit craters, including Pele’s Pit (1350-m water depth), the most hydrothermally active crater, which was formed during an earthquake swarm in 1996. Lō`ihi was not recognized as an active volcano until a sampling expedition in 1978 that led to a detailed under-standing of Lō`ihi as a juvenile oceanic intraplate volcano; it then became the de facto type location for the first stage in the development of a typical oceanic intraplate volcano. Key characteristics of this “Lō`ihi Stage” of ocean island formation include: (1) a very small volume relative to the final completed volcano, (2) a diverse suite of rock types ranging from very alkalic to tholeiitic, and (3) heterogeneous mantle sources. Since then, Lō`ihi has been the focus of substantial scientific research, with numerous sampling expeditions, leading to a detailed understanding of its volcanic history, seismic activity, petrology, geochemistry, and microbiology.
Spotlight 10: Northwest Rota-1 Seamount
William Chadwick,Robert W. Embley,Edward T. Baker,Joseph A. Resing
Oceanography , 2010,
Abstract: Northwest Rota-1 Seamount is the first place on Earth where a submarine volcanic eruption was witnessed in 2004, and, remarkably, the volcano appears to have been in a state of continuous eruption ever since. NW Rota-1 is located ~ 100 km north of Guam in the western Pacific, within the newly designated Mariana Trench Marine National Monument (http://www.fws.gov/marianastrenchmarinemonument/). With a summit depth of 520 m, it is a symmetrical cone of basaltic andesite composition formed in the subduction zone setting of the Mariana volcanic arc. It was identified as a site of particular interest in 2003 when sampling of its overlying hydrothermal plume showed very high magmatic volatile input. Consequently, it was one of several seamounts targeted for dives with a remotely operated vehicle the following year. During these dives, an actively erupting vent was discovered at a depth of 550 m; lava, fluid, and gas samples were collected; and colonies of shrimp, limpets, and crabs (some of them new species) were found living in the volcano summit’s harsh conditions.
Spotlight 11: Dom Jo o de Castro Seamount
Ricardo S. Santos,Fernando Tempera,Ana Cola?o,Frederico Cardigos
Oceanography , 2010,
Abstract: Dom Jo o de Castro is an isolated seamount located at 38°13.3’N, 26°36.2’W in the Azores archipelago (Northeast Atlantic), between the islands Terceira and S o Miguel. The shallower parts of this seamount were formed in 1720, when a volcanic cone emerged from the sea that reached ~ 1-km across and 150-m high. This cone was eroded by ocean swells in just four months, and today only a large submerged caldera (300–600 m in diameter) remains whose bottom is at 50-m depth and its top at 13-m depth. Dom Jo o Castro is an important fisheries ground both for demersal fish, such as the black-spot seabream Pagellus bogaraveo and the blue-mouth Helycolenus dactylopterus, and tuna pelagic visitors.
Spotlight 9: South Chamorro Seamount
C. Geoffrey Wheat,Patricia Fryer,Ken Takai,Samuel Hulme
Oceanography , 2010,
Abstract: Sixteen large, active serpentinite mud volcanoes exist in the Mariana forearc, the region of seafloor between the Mariana Trench and the volcanic island arc. Up to 50 km in diameter and rising as much as 2.4 km above the surrounding seafloor, these seamounts form as a consequence of subduction processes, which generate deep-seated faults that penetrate the crust and mantle of the overriding Mariana microplate to the depth of the underlying and subducting Pacific plate. Faults are observed up to 100 km west of the Mariana trench and provide a pathway for fluid, released from dehydration reactions within the subducting Pacific plate, and ground-up rock fragments to ascend. As this fluid upwells, it reacts with the overlying mantle, producing serpentine, hydrogen gas, and alkaline fluids (up to pH 12.5).
Endemicity, Biogeography, Composition, and Community Structure On a Northeast Pacific Seamount  [PDF]
Craig R. McClain, Lonny Lundsten, Micki Ream, James Barry, Andrew DeVogelaere
PLOS ONE , 2009, DOI: 10.1371/journal.pone.0004141
Abstract: The deep ocean greater than 1 km covers the majority of the earth's surface. Interspersed on the abyssal plains and continental slope are an estimated 14000 seamounts, topographic features extending 1000 m off the seafloor. A variety of hypotheses are posited that suggest the ecological, evolutionary, and oceanographic processes on seamounts differ from those governing the surrounding deep sea. The most prominent and oldest of these hypotheses, the seamount endemicity hypothesis (SMEH), states that seamounts possess a set of isolating mechanisms that produce highly endemic faunas. Here, we constructed a faunal inventory for Davidson Seamount, the first bathymetric feature to be characterized as a ‘seamount’, residing 120 km off the central California coast in approximately 3600 m of water (Fig 1). We find little support for the SMEH among megafauna of a Northeast Pacific seamount; instead, finding an assemblage of species that also occurs on adjacent continental margins. A large percentage of these species are also cosmopolitan with ranges extending over much of the Pacific Ocean Basin. Despite the similarity in composition between the seamount and non-seamount communities, we provide preliminary evidence that seamount communities may be structured differently and potentially serve as source of larvae for suboptimal, non-seamount habitats.
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