Day 16 | April 24, 2004
Pagan and Anatahan
Today we awoke, well rested, on Pagan Island. Erik, Maarten, Mike (our pilot) and I were excited to find 4 cups of coffee, waiting for us by our helicopter. It seems our island friends left us a wonderful morning gift. After we ate some breakfast, we flew to Mount Pagan in search of an access route to the one high output fumarole field that we had seen from our previous trek up the volcano, but couldn't possibly access from the summit. After a fly over, we found a gully dug out by water and rock falls that provided a path up to the field. So we landed the helicopter near the base of the mountain, then Maarten and I trekked through an a'a lava flow, then climbed 1000ft up the steep slopes of Mt. Pagan to the fumarole site, just below the crater rim (see video). We found a giant hole in the ground emitting a tremendous amount of sulfurous gas. To sample the gas, we connected all of our tubing together, tied a rope around the end, then carefully lowered our funnel deep into the seemingly bottomless vent (we couldn't actually see the bottom because the gases were too hot and too dangerous to breathe). Maarten and I were really excited to sample this gas, since our previous location was not nearly as pure a sample (that is, the summit sample location was a more diffuse, lower temperature fumarole and therefore more likely to be air contaminated than this high-output vent).
Finally, the day was getting late, and our helicopter time was running out, so we headed south towards Saipan. On the way, we flew over Guguan to make one final search for hydrothermal fields (where we saw none), then continued on to Anatahan (where we landed to refuel). Of course, as we were on the (currently) most exciting island in the Marianas, we had to take a quick look in the crater before returning to Saipan. Wow, were we excited by what we saw!
Anatahan was degassing a massive plume from the southeastern portion of the east crater. This was a very different Anatahan from the last images we viewed only 5 days ago, taken by the other team on their miniDOAS flyover. On our first pass, we did not see any particulates (ash) in the plume. Rather, the plume was very light colored and therefore the volcano appeared to be merely degassing rather than erupting. So even though there was a large plume, we felt safe to make another pass. However, on the second pass, things got very exciting (see video). We noticed that near the bottom of the crater, large fountains of dark colored material were shooting upwards several hundered feet from the floor, accompanied by gray billows of ash mixed into the massive gas plume. This suggested something different...a small eruption perhaps? We didn't stick around to find out. Once we sighted ash, it was too dangerous to fly this close, so we had to leave immediately.
Upon returning to Saipan, we visited EMO (Emergency Management Office) to report our latest observations of Anatahan. There we discovered that the seismicity had shifted from ~300 distinct events a day, which was the type of activity occurring on the previous flyover (see Dave's Log: April 17), to continuous long-period events over the last few days. After discussing the seismic and visual observations, we have decided to make one final flyover to Anatahan on Monday to measure SO2 in the now extensive gas plume.