26 February, 1999
Rodey Batiza (transcript),
John Sinton (transcript)
and Bob Waters
Summary: This dive determined the locations of contacts
between the relatively young Aldo-Kihi flow and older lava units
near 17° 26'S. On the east side, two older lava units are
present, one with slightly more sediment than the other. North
of 17° 26'S, the axis is marked by a discontinuous zone of
narrow, shallow collapses. Just west of the axis about 200 m north
of 17° 26'S, is a relatively extensive zone of diffuse hydrothermal
outflow. However, this area appears to be in decline, and one
extinct hydrothermal chimney was found there. Biota presently
is dominated by serpulids, anemones, dandelions and crabs. One
small lava flow, obviously younger than the hydrothermal activity
was seen to overlie hydrothermal sediment-coated older lavas and
biota.
The western contact of the Aldo-Kihi lava flow was followed
for several hundered meters where tongues of younger pillow lava
a few meters to several tens of meters across were seen to overlie
older lobate and locally pillow lavas. Both the western and eastern
contacts of this flow occur within about 500-700 m of the axis
in this region.
Aldo Trough (Lake Aldo) was visited during the dive and the site of the Papa Noel cutout left on top of a large pillar during NAUDUR dive 20 was seen. Since implacement on Christmas Day, 1993, a large hydrothermal edifice has grown up just to the south of the pillar and yellow colored hydrothermal sediment now shamelessly coats everything in the vicinity, including Papa Noel. Black smoke was seen to be issuing slowly from around the base of this chimney, but the upper spires appear to no longer be active.
Sample Locations:
1 17° 25.88 113° 11.67 2 17° 25.68 113° 11.91 3 17° 25.67 113° 11.97 4 17° 25.91 113° 12.31 5 17° 25.90 113° 12.28 6 17° 25.90 113° 12.52 7 17° 26.21 113° 12.68 8 17° 26.55 113° 12.74
Plots: