Alvin Dive 3343 - Feb 2, 1999

Observers: John Sinton (transcript) and Cindy Van Dover (transcript)

Pilot: Robert Williams

Launch: 18° 36.36'S; 113° 23.74'W

Objectives: Work south from Animal Farm, exploring axis. Watch for evidence of different eruptive episodes/features. Test "musset pot" and search for suitable "bio-dive" site.


  • Evidence at animal farm suggests AF flow is dammed by older (?) lobate lavas to east and, hence flowed to the west. Investigate whether or not this is true and nature of "dam".
  • There is a slight bend in the axis bewttrwen WPs 2 & #. To north, axis aoppears to be more strongly fissured, to south there are good channels. Fissures right-step to north.
  • Region arounf WP4, west of axis charasterized by well-developed, low backscatter channels (?). Visit these.
  • WP5 on axial high, is it constructional or what?
  • Fundamental boundary in axial strike, and seafloor character between WPs 5 and 6. Attempt to
  • reach the boundary.
  • Summary: This dive traversed the axis at least four times. All lavas on this dive are extremely glassy and all areas visited had at least a thin coating of sediment. The eastern flank is dominated by lobate lavas with some pillows, locally with abundant buds. The axial region typically contains collapsed lobate lavas with a variety of sheet flows lying in the collapsed areas. For much of the dive there is a tendency for asymmetric collapse, mostly down to the west with sheet flows primarily flowing westward. Most collapsed areas are relatively small, less than a few meters deep although one area near 18° 37.65'S, 113° 24.25'W is 12 m deeper than the surrounding lobate surface. An extensive area of sheet flows is present on the western flank between about 18°37.5'S and 18°38.4'S. The heaviest sediment cover observed was on the east flank near 18° 37.4'S. Contacts between various lava morphologies, e.g. between lobate and sheet lavas, were extremely common although it is unclear which of these, if any, represent boundaries between the products of different eruptive events. Some lobate, and or pillow lavas on the east flank may be an older lava series.
    Diffuse hydrothermal venting was found at two sites - Animal Farm near 18°36.48'S, 113° 23.95'S, and an area about 570m along strike to the SW near 18° 36.78'S, 113° 24.09'W. Alvin window temperature indicates an approximately 0.4°C anomaly at the latter site. The part of the Animal Farm site visited during this dive appears to be less active with less vital animal communities present than in in 1993 when this site was visited during NAUDUR dive 12. Animal Farm may be evolving into Pet Cemetary. Approximately 4.5 km of track was covered during this dive and ten samples collected, of which one was biological and the other nine, primarily lava fragments, some of which had attached biota.


  • Transponder net, targets and conversions
  • Navigation Plot (GMT)
  • Navigation Plot (dot cloud)
  • Depth Plot
  • Heading Plot
  • Magnetics Plot 1
  • Magnetics Plot 2
  • Temperature Plot 1
  • Temperature Plot 2
  • Sample locations:

    Sample # Latitude (°S) Longitude (°W)
    1      18° 36.39      113° 23.78
    2      18° 36.45      113° 23.96
    3      18° 36.45      113° 23.96
    4      18° 36.66      113° 24.04
    5      18° 37.06      113° 24.06
    6      18° 37.49      113° 24.14
    7      18° 37.74      113° 24.40
    8      18° 38.52      113° 24.40
    9      18° 38.77      113° 24.53
    10     18° 38.90      113° 24.55