Alvin Dive 3344 - Feb 3,1999

Observers: Ken Macdonald (transcript) and Ken Rubin (transcript)

Pilot: Stephen Faluotico

Launch: 18° 34.80' S, 113° 23.85' W


  • Investigate nature of axial lava morphologies
  • Detailed mapping of contact between lava motphologies on axis
  • Investigate potential lava dam on east side of spreading center
  • Heavily sample observed lava units
  • Notes:

  • Sidescan record shows very smooth and fissured lavas to the south of ~ -18° 35' S
  • Sidescan record shows apparent lava mounds north of ~ -18° 35' S
  • Contact between lava types is predicted to occur between waypoints 3 and 4. Actual dive track to be determined during the dive.
  • Attempt to overlap this dive track with the start of Dive 3343 track at "Animal Farm".
  • Continue beyond way point 6 as time permit
  • Dive Summary: Macdonald and Rubin landed on the east side of the OSC basin on age 1.5 pillow lavas. We traversed the axis several times heading generally south, encountering a contact between age 1 sheet flows/lobate flows(the "Animal Farm" flow?)and age 1.5 pillow lavas. Near the OSC tip, the outcrop is all age 1.5 pillows; we climbed up several pillow mounds and ridges which were several tens of meters high and sampled them. These were seen clearly in the DSL 120 side scan sonar records. To the south, we encountered age 1 sheets and lobates often in lava channels. We explored 3 lava channels up to ~100-150m wide. We followed them uphill to their source regions which were eruptive fissures 2-3 m wide and collapsed lava lakes. The tops of the lava channel levees were usually lobate flows of age 1, the edges of the floors were often jumbled sheet flows grading to folded sheet flows and finally to flat, striated sheet flows toward the centers of the lava channels. We traversed back and forth across the boundary between age 1 sheets/lobates and age 1.5 pillows many times; the older pillow lavas reappeared near the end of the dive downslope from the summit. We collected 12 rock samples from both sides of the age 1/1.5 contact. No hydrothermal activity was observed, but we saw some yellowish sediment which may have had a hydrothermal component. We stopped a few hundred m short of animal farm.


  • Navigation Plot (GMT)
  • Navigation Plot (dot cloud)
  • Depth Plot
  • Heading Plot
  • Magnetics Plot 1
  • Magnetics Plot 2
  • Temperature Plot