Day 4 | April 12, 2004
The Reconnaissance Fly-over
In preparation for our sampling expedition, we did a 6-hour fly-over by fixed wing aircraft along the 370-mile long volcanic chain. Initially, we maintained a 7000 ft altitude to get a broad overview of the islands. We are particularly interested in sighting helicopter landing spots as well as potential sampling locations for rocks and gases.
After 3 hours, we reached the northernmost islands, Asuncion, Maug and Uracas. We descended to about 3000 ft to get a better view of the volcanoes. Uracas, the northern-most volcano of the chain, is also the Marianas' most active volcano. This small island is completely covered by recent lava flows and ash.
The next volcano to the south is Maug, a partially submerged caldera. Maug consists of 3 islands. On our trip we will set up a base camp on Maug from where we will access Uracas to the north and Asuncion to the south. Asuncion is a symmetrical cone with very steep slopes, covered in vegetation.
Towards the end of our fly-over, we reached Anatahan which erupted in May, 2003. The flanks of Anatahan are still completely covered with ash from last year's eruption. We had a good view of the active crater. At the bottom of the crater are numerous fumaroles (gas vents) and what we believe is a solidified lava lake. As we flew by, a small explosion occurred. Gas and ash erupted from a small vent that opened in the lava lake. A close look showed glowing red lava below. Clearly, Anatahan is still active.
Also today, we had a visit with Juan Camacho and company over at the Emergency Management Office (EMO) to work on permits, which are required for us to land at several of the islands that are bird sanctuaries (Guguan, Agrigan and Uracas). While we were there, we got to see the seismic activity records for the two seismographs at Anatahan; it was busy! There has been lots of seismic activity there over the past 2 weeks, so much so that it appears that it might be dangerous to approach the East Crater. We have a lot of work to do on the west side of the island, which is sheltered from the current activity of the East crater, but we had hoped to sample rocks from the western wall of the caldera, and gases from the East Crater as well.