March 13, 2001 to June 2, 2001
Monterey to Hawaii and back
May 9, 2001: Leg 4; Day 1
Jenny Paduan writes: Aloha again! It was nice to be off the ship for a week of calm and quiet. I went to the Big Island, and back to the lava! Kilauea is still producing pahoehoe surface flows from Pu'u O'o. We were not able to dive today due to strong winds and currents at our planned dive site off of Oahu. We will try again tomorrow.
In the picture on the right, I have just dipped a rock hammer into red-hot lava. You can see the newly created rock, still slightly red, dripping from the end of the hammer. The temperature of this flow is about 1130 degrees Celsius. The lava flow in the background erupted between 1985 and 1992.
Dave Clague writes: We departed Honolulu at 8 a.m. today and steamed west and then north along the west coast of Oahu in calm seas and low winds. Our target site for the first dive of leg 4 was about 5 hours steam from Honolulu to the northwest of Oahu. The target was a flat-topped lava cone that has a small cone on its top and an apparent water column anomaly suggestive of bubbling or hot water discharge. Either possibility would be consistent with recent volcanic or hydrothermal activity, suggesting that the cone might be volcanically active. As we rounded the northwest point on Oahu we could see a wind line and white caps beyond. The sea state increased and the winds rose to nearly 30 knots before we arrived at our target. With surface currents of about 1 knot in addition to the seas and wind, we were unable to hold station with the ship and had to move on to an alternate site. We had previously selected several interesting sites on blocks in the upper part of the Waianae landslide, but these turned out to be located within a military explosive dump site and we decided we had already seen enough ordinance on this trip. We steamed to the northwest to a site in the deeper part of the channel between Oahu and Kauai where, at about 4 p.m., we began a dive on several small rejuvenated stage volcanic cones at a depth of about 2900 m.
The dive began in a moderately sediment covered region, but fragments of lava projected through the sediment. Each block of lava had a trail of gravel behind it, showing the orientation of the strong bottom currents in the region. We continued downslope with little change in bottom characteristics, crossed through a small valley between two cones and then started up the slope on the second cone. The bottom remained gentle with low lava outcrops and gravel in a surface mainly of fine sediment. The SeaBeam bathymetry indicated that the cone was low and broad, but we found it to be smaller across and steeper. The steep slope consisted on sheet-like lava flows with shallow channels. During this short dive the Kraft manipulator began to misbehave (it developed a jerky movement) that made sampling challenging, to say the least. We decided to end the dive and try to repair the arm. The dive recovered 14 samples of lava from two volcanic vent structures and established that both these cones are quite old, having moderate sediment cover and thick Mn-oxide crusts on the rock samples. We will cut these samples today and determine whether we succeeded in collecting volcanic glass that would allow us to characterize the volatile and rare gas components of these lavas. The day ended about midnight when we finished the initial laboratory processing of the samples. Overnight we will steam to the south flank of Kauai where we will dive on a series of similar rejuvenated-stage volcanic cones related to the Koloa Volcanics on Kauai.