(e.g., Kelley et al., 2002; Fornari et al., 2012). Mid-ocean
ridge eruptions provide windows into rapidly changing
magmatic, hydrothermal, and deep-sea biological processes
(e.g., Delaney et al., 1998), so there has been great interest
in detecting eruptions or intrusions, followed by rapidly
organized seagoing response efforts to study these interplays (see reviews in Baker et al., 2012; Rubin et al.,
2012). Such field studies, which began in the early 1990s,
have largely been in response to remotely detected seismicity or serendipitous discovery. Despite the logistical difficulty of getting research vessels, equipment, and crew
together on short notice, thirty-five recognized events have
been responded to on submarine volcanoes over the world
(i.e., at mid-ocean ridges and arc and intraplate seamounts;
Baker et al., 2012). This list includes eleven historical eruptions at mid-ocean ridges (Rubin et al., 2012). As of this
writing, the most recent of these eruptions, which occurred
at Axial Seamount in 2011 (on the Juan de Fuca), was a triumph of prior planning and deployment of modern instrumentation, so that the geophysical, geodetic, and
geological characteristics of the event were captured in
exquisite detail (Caress et al., 2012; Chadwick et al.,
2012; Dziak et al., 2012). The newest approaches in submarine eruption studies include autonomous detection stations, autonomous vehicle development for response
efforts, and the establishment of permanent seafloor observatories. These will provide extraordinary research opportunities at a handful of sites, but active monitoring of
most of the global ridge system will take a concerted effort
by the international scientific community, as well as many
more interested scientists and infrastructure to conduct
these rapid response research efforts.
Summary
The global mid-ocean ridge system is a vast, complicated
array of volcanoes, the great majority of which remain
unvisited and sparsely sampled. Detailed studies at a few
dozen sites reveal patterns of volcanic style, magmatic
processes, and erupted compositions that generally reflect
variations in spreading rate, magma supply, mantle composition, and proximity to ridge discontinuities and
hotspots. Such studies also reveal the range of site-specific
geological conditions that affect MORB composition and
mid-ocean ridge volcanism. These effects are being studied in ever more locales at ever higher resolution to understand the spatial and temporal scales of ocean ridge
magmatic processes, revealing how mid-ocean ridge volcanoes operate and how they sample the underlying mantle. Combined petrological, geochemical, geophysical,
and geological data about mid-ocean ridges indicate that
inferred mantle compositions are significantly modified
in range, magnitude, and length scale at mid-ocean ridges
by preeruptive magmatic processes such as magma residence and transport through the upper mantle and lower
crust. Submarine eruptions construct new ocean crust
and are a primary agent for the transfer of heat, chemicals,
and microbes from the Earth’s mantle or crust into the
overlying ocean. Studying these eruptions is therefore
important as well for a complete understanding of the
chemistry and biology of the deep sea.
Bibliography
Agranier, A., et al., 2005. The spectra of isotopic heterogeneities
along the mid-Atlantic Ridge. Earth and Planetary Science Letters, 238, 96–109.
Allègre, C. J., Hamelin, B., and Dupre, B., 1984. Statistical analysis
of isotopic ratios in MORB: the mantle blob cluster model and
the convective regime of the mantle. Earth and Planetary Science Letters, 71, 71–84.
Arevalo, R., Jr., and McDonough, W. F., 2010. Chemical variations
and regional diversity observed in MORB. Chemical Geology,
271, 70–85.
Asimow, P. D., Dixon, J. E., and Langmuir, C. H., 2004. A hydrous
melting and fractionation model for mid-ocean ridge basalts:
application to the Mid-Atlantic Ridge near the Azores. Geochemistry, Geophysics, Geosystems, 5, Q01E16.
Baker, E. T., Massoth, G. J., and Feely, R.A., 1987. Cataclysmic
hydrothermal venting on the Juan de Fuca Ridge. Nature, 329
(6135), 149–151.
Baker, E. T., Lupton, J. E., Resing, J. A., Baumberger, T., Lilley,
M. D., Walker, S. L., and Rubin, K. H., 2011. Unique event
plumes from a 2008 eruption on the Northeast Lau Spreading
Center. Geochemistry, Geophysics, Geosystems, 12, Q0AF02.
Baker, E. T., Chadwick, W. W., Jr., Cowen, J. P., Dziak, R. P., Rubin,
K. H., and Fornari, D. J., 2012. Hydrothermal discharge during
submarine eruptions: the importance of detection, response,
and new technology. Oceanography, 25, 128–141.
Ballard, R. D., and van Andel, T. H., 1977. Morphology and tectonics of the inner rift valley at lat 36
50
0 N on the Mid- Atlantic
Ridge, Geol. Soc. Am. Bull., 88, 507–530.
Ballard, R. D., van Andel, T. H., and Holcomb, R. T., 1982. The
Galapagos Rift at 86
W 5. Variations in volcanism, structure,
and hydrothermal activity along a 30-kilometer segment of the
rift valley. Journal of Geophysical Research, 87, 1149–1161.
Bergmanis, E., Sinton, J. M., and Rubin, K. H., 2007. Recent eruptive history and Magma reservoir dynamics on the Southern East
Pacific Rise at 17.5
o
S. Geochemistry, Geophysics, Geosystems,
8, Q12O06.
Bowles, J., Gee, J. S., Kent, D. V., Perfit, M. R., Soule, S. A., and
Fornari, D. J., 2006. Paleointensity applications to timing and
extent of eruptive activity, 9–10
N East Pacific Rise. Geochemistry, Geophysics, Geosystems, 7, Q06006.
Bowles, J. A., Colman, A., McClinton, J. T., Sinton, J. M., White,
S. M., and Rubin, K. H., 2014. Eruptive timing and 200 year
episodicity at 92
W on the hot spot-influenced Galapagos
Spreading Center derived from geomagnetic paleointensity.
Geochemistry, Geophysics, Geosystems, 15, 2211–2224.
Bown, J. W., and White, R. S., 1994. Variation with spreading rate
of oceanic crustal thickness and geochemistry. Earth and Planetary Science Letters, 121, 435–451.
Buck, W. R., Carbotte, S. M., and Mutter, C., 1997. Controls on
extrusion at mid-ocean ridges. Geology, 25, 935–938.
Cann, J. R., 1974. A model for oceanic crustal structure developed.
Geophysical Journal of the Royal Astronomical Society, 39,
169–187.
Cannat, M., Sauter, D., Bezos, A., Meyzen, C., Humler, E., and Le
Rigoleur, M., 2008. Spreading rate, spreading obliquity, and
melt supply at the ultraslow spreading Southwest Indian Ridge.
Geochemistry, Geophysics, Geosystems, 9, Q04002.
Carbotte, S. M., Canales, J. P., Nedimović, M. R., Carton, H., and
Mutter, J. C., 2012. Recent seismic studies at the East Pacific
Rise 8
20
0
–10
10
0 N and endeavour segment: Insights into
510
MID-OCEAN RIDGE MAGMATISM AND VOLCANISM
ridge eruptions provide windows into rapidly changing
magmatic, hydrothermal, and deep-sea biological processes
(e.g., Delaney et al., 1998), so there has been great interest
in detecting eruptions or intrusions, followed by rapidly
organized seagoing response efforts to study these interplays (see reviews in Baker et al., 2012; Rubin et al.,
2012). Such field studies, which began in the early 1990s,
have largely been in response to remotely detected seismicity or serendipitous discovery. Despite the logistical difficulty of getting research vessels, equipment, and crew
together on short notice, thirty-five recognized events have
been responded to on submarine volcanoes over the world
(i.e., at mid-ocean ridges and arc and intraplate seamounts;
Baker et al., 2012). This list includes eleven historical eruptions at mid-ocean ridges (Rubin et al., 2012). As of this
writing, the most recent of these eruptions, which occurred
at Axial Seamount in 2011 (on the Juan de Fuca), was a triumph of prior planning and deployment of modern instrumentation, so that the geophysical, geodetic, and
geological characteristics of the event were captured in
exquisite detail (Caress et al., 2012; Chadwick et al.,
2012; Dziak et al., 2012). The newest approaches in submarine eruption studies include autonomous detection stations, autonomous vehicle development for response
efforts, and the establishment of permanent seafloor observatories. These will provide extraordinary research opportunities at a handful of sites, but active monitoring of
most of the global ridge system will take a concerted effort
by the international scientific community, as well as many
more interested scientists and infrastructure to conduct
these rapid response research efforts.
Summary
The global mid-ocean ridge system is a vast, complicated
array of volcanoes, the great majority of which remain
unvisited and sparsely sampled. Detailed studies at a few
dozen sites reveal patterns of volcanic style, magmatic
processes, and erupted compositions that generally reflect
variations in spreading rate, magma supply, mantle composition, and proximity to ridge discontinuities and
hotspots. Such studies also reveal the range of site-specific
geological conditions that affect MORB composition and
mid-ocean ridge volcanism. These effects are being studied in ever more locales at ever higher resolution to understand the spatial and temporal scales of ocean ridge
magmatic processes, revealing how mid-ocean ridge volcanoes operate and how they sample the underlying mantle. Combined petrological, geochemical, geophysical,
and geological data about mid-ocean ridges indicate that
inferred mantle compositions are significantly modified
in range, magnitude, and length scale at mid-ocean ridges
by preeruptive magmatic processes such as magma residence and transport through the upper mantle and lower
crust. Submarine eruptions construct new ocean crust
and are a primary agent for the transfer of heat, chemicals,
and microbes from the Earth’s mantle or crust into the
overlying ocean. Studying these eruptions is therefore
important as well for a complete understanding of the
chemistry and biology of the deep sea.
Bibliography
Agranier, A., et al., 2005. The spectra of isotopic heterogeneities
along the mid-Atlantic Ridge. Earth and Planetary Science Letters, 238, 96–109.
Allègre, C. J., Hamelin, B., and Dupre, B., 1984. Statistical analysis
of isotopic ratios in MORB: the mantle blob cluster model and
the convective regime of the mantle. Earth and Planetary Science Letters, 71, 71–84.
Arevalo, R., Jr., and McDonough, W. F., 2010. Chemical variations
and regional diversity observed in MORB. Chemical Geology,
271, 70–85.
Asimow, P. D., Dixon, J. E., and Langmuir, C. H., 2004. A hydrous
melting and fractionation model for mid-ocean ridge basalts:
application to the Mid-Atlantic Ridge near the Azores. Geochemistry, Geophysics, Geosystems, 5, Q01E16.
Baker, E. T., Massoth, G. J., and Feely, R.A., 1987. Cataclysmic
hydrothermal venting on the Juan de Fuca Ridge. Nature, 329
(6135), 149–151.
Baker, E. T., Lupton, J. E., Resing, J. A., Baumberger, T., Lilley,
M. D., Walker, S. L., and Rubin, K. H., 2011. Unique event
plumes from a 2008 eruption on the Northeast Lau Spreading
Center. Geochemistry, Geophysics, Geosystems, 12, Q0AF02.
Baker, E. T., Chadwick, W. W., Jr., Cowen, J. P., Dziak, R. P., Rubin,
K. H., and Fornari, D. J., 2012. Hydrothermal discharge during
submarine eruptions: the importance of detection, response,
and new technology. Oceanography, 25, 128–141.
Ballard, R. D., and van Andel, T. H., 1977. Morphology and tectonics of the inner rift valley at lat 36
50
0 N on the Mid- Atlantic
Ridge, Geol. Soc. Am. Bull., 88, 507–530.
Ballard, R. D., van Andel, T. H., and Holcomb, R. T., 1982. The
Galapagos Rift at 86
W 5. Variations in volcanism, structure,
and hydrothermal activity along a 30-kilometer segment of the
rift valley. Journal of Geophysical Research, 87, 1149–1161.
Bergmanis, E., Sinton, J. M., and Rubin, K. H., 2007. Recent eruptive history and Magma reservoir dynamics on the Southern East
Pacific Rise at 17.5
o
S. Geochemistry, Geophysics, Geosystems,
8, Q12O06.
Bowles, J., Gee, J. S., Kent, D. V., Perfit, M. R., Soule, S. A., and
Fornari, D. J., 2006. Paleointensity applications to timing and
extent of eruptive activity, 9–10
N East Pacific Rise. Geochemistry, Geophysics, Geosystems, 7, Q06006.
Bowles, J. A., Colman, A., McClinton, J. T., Sinton, J. M., White,
S. M., and Rubin, K. H., 2014. Eruptive timing and 200 year
episodicity at 92
W on the hot spot-influenced Galapagos
Spreading Center derived from geomagnetic paleointensity.
Geochemistry, Geophysics, Geosystems, 15, 2211–2224.
Bown, J. W., and White, R. S., 1994. Variation with spreading rate
of oceanic crustal thickness and geochemistry. Earth and Planetary Science Letters, 121, 435–451.
Buck, W. R., Carbotte, S. M., and Mutter, C., 1997. Controls on
extrusion at mid-ocean ridges. Geology, 25, 935–938.
Cann, J. R., 1974. A model for oceanic crustal structure developed.
Geophysical Journal of the Royal Astronomical Society, 39,
169–187.
Cannat, M., Sauter, D., Bezos, A., Meyzen, C., Humler, E., and Le
Rigoleur, M., 2008. Spreading rate, spreading obliquity, and
melt supply at the ultraslow spreading Southwest Indian Ridge.
Geochemistry, Geophysics, Geosystems, 9, Q04002.
Carbotte, S. M., Canales, J. P., Nedimović, M. R., Carton, H., and
Mutter, J. C., 2012. Recent seismic studies at the East Pacific
Rise 8
20
0
–10
10
0 N and endeavour segment: Insights into
510
MID-OCEAN RIDGE MAGMATISM AND VOLCANISM