visited by Pisces IV (dive 1730) and Alvin (dives 1925 and 1928). 

 The vents, usually associated with small collapses, cracks and 

 boundaries between the flow lobes, are characterized by 

 widespread bacterial colonies and isolated colonies of larger 

 animals. Although no high-temperature venting (maximum measured 

 temperature was 25°C) was observed during these dives, an 

 isolated 1 m pyritic chimney recovered on Pisces dive 1730 

 suggests that there have been localized, short-lived episodes of 

 high-temperature venting within this field. 



DISCUSSION AND CONCLUSIONS 



An understanding of the volcanic and hydrothermal processes 

 occurring in and around the caldera are important to developing a 

 better model of the dynamics of submarine volcano evolution and 

 concomitant hydrothermalism. Some of the major questions 

 relating to the interplay between volcanic and hydrothermal 

 processes may be addressed at Axial Volcano. For example, the 

 lack of large high-temperature vent fields (and consequent lack 

 of a significant plume) is probably due to some combination of 

 factors related to the frequency of volcanism, present stage of 

 the volcano- tectonic cycle, and the physics and chemistry of the 

 hydrothermal process active at the water depth and environment of 

 Axial Volcano. Because of its shallow depth (and consequent 

 accessibility to both Alvin and Pisces submersibles ) and its 

 manageable size, the ASHES vent field is becoming a laboratory 

 for developing better quantitative models of near-field vent 

 processes and testing vent monitoring devices. Axial Volcano is 

 a critical seafloor feature for study both of the evolution of a 

 still active ( volcanically and hydrothermal ly ) submarine volcano 

 and in its role in the recent evolution of the Juan de Fuca 

 Ridge. 



LITERATURE CITED 



CASM, 1985. Hydrothermal vents on an axial seamount on the Juan 

 de Fuca Ridge. Nature , Vol. 313, No. 5999, pp. 212-214. 



Crane, F. Aikman, R. W. Embley, S. Hammond and A. Malahoff, 1985. 

 The distribution of geothermal fields on the Juan de Fuca 

 Ridge. J^ Geophys . Res. , Vol. 90, No. Bl, pp. 727-744. 



Fox, C. G., K. M. Murphy and R. W. Embley, 1987. Automated 



display and statistical analysis of interpreted deep-sea 

 bottom photographs. Mar. Geol . , Vol. 78, pp. 199-216. 



Malahoff, A., 1985. Hydrothermal vents and polymetallic sulfides 

 of the Galapagos and Gorda/Juan de Fuca Ridge systems and of 

 submarine volcanos. Bull . Biol . Soc. of Washington , No. 6, 

 pp. 19-42. 



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