Alvin Dive 3363 - Summary

Ken Macdonald (transcript)

Ken M/Blee/ Phil (PIT)


  1. To define the contacts of the youngest (Aldo-Kihi or L0) flow between the Ken R/Scott dive and the Japanese dives, ie, near 18º31-33' S.
  2. To examine an area of the axis which appears to be defined by an axial ridge about 10-20 m high on the east side (mostly lobates, some pillows); and a parallel zone of lineated collapses ~300m to the west; which is the true "axis"?
  3. To check out a bed of mussels located with ARGO II in 1996.

Summary: This dive was located on the crest of the EPR between 17º31.7'-33' S. It was a PIT dive so only one scientific observer was aboard, Macdonald, who sat on the stbd side. We crossed the contact between the Aldo-Kihi flow of age 1/2 to an older flow of 1.0 or older 8 times, 4 times on the east and 4 times on the west. The contact was clearly seen on the 1996 DSL 120 records. On the east side it is a positive return associated with an age 1 pillow ridge east of the axis which acts as a constructional dam to the younger AK flow. On the west side, the AK flow is seen as a low reflectivity area of younger, smoother flows (mostly lobates and sheets), interfingering with the older rougher flows (mostly pillows here) of age 1 or more. Within the younger unit there were 3 collapsed lava lakes which we explored. The floor of the southernmost lake is resurfaced with a flow which may be younger than AK, or perhaps a late phase of the AK eruption, and should be dated by Rubin, see samples 3363-7,8.



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