Conical Vent



Latitude: 19.542οN                  Longitude: 146.648οE             Depth: 3144 m bsl

Conical Seamount is a smooth sided, nearly circular forearc serpentine mud volcano with a slightly flattened summit region (Fryer, 1996) that is located adjacent to a large forearc graben (Fryer et al., 1990; Fryer, 1992; Newsom, 1992). Conical Seamount is considered active because of the discovery of recent mud extrusions and the venting of fluids with deep slab origins [Fryer and Mottl, 1992]. The fluids are actively flowing through carbonate and silicate chimneys and have elevated pH, high alkalinity and enrichments in CH4, SiO2, SO42-, and H2S. Methane and sulfate in the fluids are probably generated during serpentinization reactions between peridotite and slab derived fluids (Fryer, 1990). Some bacterial mats, small limpets and gastropods are associated with these vents.

Table 1: Operations history for Conical vent

Ship/ Platform Operation Year Dive Number References
KR06-15 Kaiko Not found 2006 November  0369 JAMSTEC E-library of Deep-sea Images (JEDI) (note: search “Conical”)

KR06-15 cruise report

Not found SeaMARK II bathymetry data Not found Not found Fryer et al., 1996; Fryer et al., 1992
Not found Seasat A Satellite Scatterometer (SASS) data Not found Not found Fryer et al., 1996; Fryer et al., 1992
TN-154 Thompson/ ROV Jason-2 Not found 2003 April J2-032 Woods Hole Oceanographic Institution: ROV JASON/MEDEA: Operations Summary (note: click “Files- operations summary”)
YK03-07 Yokosuka/ Shinkai 6500 Not found 2003 September 785 YK03-07 cruise report

Table 2: Vent activity and host rocks

Activity and Host Rocks References
Activity Active mud volcanism Fryer and Mottl., 1992; Fryer., 1990;  IODP-MCME 366 Proposal; Savov et al., 2005
Host Rocks Serpentinized harzburgite and dunite Fryer et al., 1990; Savov et al., 2005

Table 3: Vent fluid characteristics

Bottom seawater Vent Fluids References
Distance from the trench (km) 90 IODP-MCME 366 Proposal
Temperature (οC) 13.5 οC (hole 780D); 1.5οC Fryer et al., 1990(c); Mottl et al., 2003
pH 7.72 9.28 Fryer et al., 1990
>9.2, 12.5 Hulme et al., 2010, Fryer et al., 1990 b
Composition Indicate deep seated serpentinization sources, enriched in CH4, SiO2, SO42-, H2S Fryer et al., 1990
Alkalinity (meq/kg) 2.3 High, 41 Fryer et al., 1990
Clorinity (mmol/kg) 542 260 IODP-MCME 366 Proposal
CH4 (mmol/kg) 4×10-7 2±1 Mottl et al., 2003
Mn (μmol/kg) 0 <0.01 IODP-MCME 366 Proposal
Fe (μmol/kg) 0 2 IODP-MCME 366 Proposal
Sulfate  (mmol/kg) 28 46 IODP-MCME 366 Proposal
Mg (mmol/kg) 0.009 Fryer et al., 1990 b
Ca (mmol/kg) 0.6 Fryer et al., 1990 b
Na (mmol/kg) 466 390 IODP-MCME 366 Proposal
K (mmol/kg) 10.1 15 IODP-MCME 366 Proposal
Li (μmol/kg) 26 1.6 IODP-MCME 366 Proposal
Rb (μmol/kg) 1.37 7.8 IODP-MCME 366 Proposal
Sr (μmol/kg) 90 20 IODP-MCME 366 Proposal
Ba (μmol/kg) 0.14 0.1 IODP-MCME 366 Proposal
B (μmol/kg) 410 3900 IODP-MCME 366 Proposal
Si (μmol/kg) 190 60 IODP-MCME 366 Proposal

* IODP-MCME 366- International Ocean Discovery Program-Mariana Convergent Margin Expedition 366.

Table 4: Vent Biology

General name Phylum Class/Order Family Genus/Species References
Bacterial mats Bacteria Fryer et al., 1990
Fish Chordata Anguilliformes JAMSTEC E-library of Deep-sea Images (JEDI) (note: search “Conical seamount”)
Gastropods Mollusca Fryer et al., 1990
Sea anemone Cnidaria Actiniaria Boloceroididae JAMSTEC E-library of Deep-sea Images (JEDI) (note: search “Conical seamount”)
Sea cucumbers Echinoderms Holothuroidea Pelagothuriidae Enypniastes eximia JAMSTEC E-library of Deep-sea Images (JEDI) (note: search “Conical seamount”)
Shrimp Arthropoda Decapoda JAMSTEC E-library of Deep-sea Images (JEDI) (note: search “Conical seamount”)
Small Limpets Mollusca Fryer et al., 1990
Sponge Porifera JAMSTEC E-library of Deep-sea Images (JEDI) (note: search “Conical seamount”)


Video Links: None known


  1. Fryer, P., Saboda, K. L., Johnson, L. B., Mackay, M. E., Moore, G. F., Sto¡ers, P., 1990. Conical Seamount: SeaMARK II, Alvin submersible, and seismic reflection studies. Proc. ODP Init. Rep. 125, 69-80.
  2. Fryer, P., Mottl, M. J., 1992. Lithology, mineralogy, and origin of serpentine muds recovered from Conical and Torishima forearc seamounts: results of Leg 125 drilling, Proc. ODP Sci. Results 125, 343-362.
  3. Fryer, P, 1996. Evolution of the Mariana convergent plate margin system. Reviews of Geophysics 31 (1), 89-125.
  4. Mottl, M. J., Komor, S. C., Fryer, P., Moyer, C. L., 2003. Deep-slab fluids fuel extremophilic Archaea on a Mariana forearc serpentinite mud volcano: Ocean Drilling Program Leg 195. Geochemistry, Geophysics, Geosystems 4 (11) 9009, doi: 10.1029/2003GC000588.
  5. Savov, I. P., Ryan, J. G., D’Antonio, M., Kelley, K., Mattie, P., 2005. Geochemistry of serpentinized peridotites from the Mariana Forearc Conical Seamount, ODP Leg 125: Implications for the elemental recycling at subduction zones. Geochem.Geophys. Geosyst., 6, Q04J15, doi: 10.1029/2004GC000777.

Website References:

  1. J-EDI JAMSTEC (Japan Agency for Marine Earth Science and Technology) E-library of Deep-sea Images: (accessed 11/24/2015)
  2. Woods Hole Oceanographic Institution: ROV JASON/MEDEA: Operations Summary (accessed 11/24/2015)

Cruise Reports:

  1. IODP Mariana Convergent Margin Expedition 366, unpublished IODP proposal (accessed 01/19/2016)
  2. Kairei cruise report KR06-15 (accessed 01/19/2016)
  3. Yokosuka cruise report YK03-07 (accessed 01/19/2016)