Daily Journal
Anatahan
Anatahan crater with lava dome
Ray Chong pointing at seismic events |
Since its first historical eruption in May 2003, Anatahan has remained active. In the past few weeks, the
seismic station on the island recorded as many as 3000 earthquakes per day. Both the US Geological Survey
and the Emergency Management Office (EMO) are monitoring the volcano closely. Because Anatahan is a major
target of our expedition, we did a helicopter over-flight to make more observations. When we climbed over
the rim into the active crater, we noticed right away that there was much more gas coming from the crater
then we had observed during our initial flyover just days ago. You can see a lot of white
steam and, if you look closely, a steaming lake on the left. In the center of the photo, a small explosion
is apparent, similar to the one we saw on the flyover. Today's explosion, however, was more energetic,
releasing more gas [movie]. The seismic events that are associated with these small explosions were recorded
by EMO, and seismic technician Ray Chong is pointing out the events that occurred during the time of our helicopter
over-flight.
Seismograph at EMO
One of the goals of our expedition is to measure the gas emissions from the volcanoes using the mini-DOAS.
We mounted the mini-DOAS on the helicopter, pointing the telescope vertically out of the window. You can see the
red fiber optics cable that leads from the telescope to the instrument. Toby is using a computer to record the data
during the flight. We traversed under the volcanic plume and successfully made measurements of the SO2 emissions
from the volcano. The graph below shows the increase in SO2 content as we flew under the plume.
We did several traverses and we will use this data to calculate the flux of SO2 from the
volcano and compare it with the amount we measured in May 2003, only ten days after the eruption. On our way back to
Saipan, we briefly landed at a safe location on the eastern side of the island, refueled, checked our notes and returned
to Saipan.
Mini-DOAS mounted in the helicopter
Sulfur dioxide content of the Anatahan plume. Two transects are show
Alison and Toby checking notes on the E-meadow
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