On To Day 18Return To Day 16Day 17. Half Way There

By Debbie Smith

October 12, 1998. We are at the half way point of our cruise, and this Daily Flash is written from my perspective as chief scientist. Everyone is working very hard to make the cruise a success, and the data that we have collected to date are providing exciting new views of the submarine Puna Ridge. We have already learned a lot about the volcanic and tectonic processes acting at the Puna Ridge, and it has been especially exciting for me.

Schematic of Volcanic activity
A cartoon of how eruptions might occur at the Mid-Atlantic Ridge.  Fissures are shown as red/yellow lines.  Lava erupts from fissures and flows away in channels and tubes to form flat-topped terraces and cratered volcanoes.  These processes are likely to occur at the Puna Ridge as well.

In September, Joe Cann from the University of Leeds and I submitted a paper to the Journal of Geophysical Research in which we re-interpreted the volcanic morphology of the slow-spreading Mid-Atlantic Ridge based on our understanding of the morphology of the Puna Ridge at that time. Our idea is that the submarine flat-topped terraces built at the Mid-Atlantic Ridge and the Puna Ridge are secondary features that emerge from within a lava flow, not primary vents fed directly from a dike as most people believe. We also consider that lava is transported several kilometers away from the sites of the fissure eruptions in lava tubes or channels to form the terraces. This is much like the flows on the subaerial East Rift Zone of Kilauea which are transported long distances, eventually ending at the sea. Existing data were not sufficient to provide definitive proof for our interpretation, however.

Dave DuBois (L. Dolby)
Dave DuBois moonlighting as baker. (L. Dolby)

Although we will collect a lot more data during the second half of our cruise, and all the data will have to be analyzed in detail, a preliminary look at the new sonar images suggests that the flanks of the Puna Ridge and the volcanic ridges at the Mid-Atlantic Ridge may be primarily coated by lava fed through lava tubes and channels, and that our interpretation is correct. The photographic imagery yet to be obtained will help us to pin this down more fully. Whether our ideas turn out to be correct or not, the results from this cruise will allow us to understand more fully how magmatic and volcanic processes work at both Kilauea volcano and mid-ocean ridges.

We are all putting in long hours during the cruise, and are often tired. Nonetheless, fun moments always occur during the day. Rumor had it that there was a cookie elf in the ship’s hold baking our favorite cookies nightly. Dave DuBois is shown here proudly displaying the logo of these cookies suggesting that he may be that elf.

Ship Tracks October 10 through October 12

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