This year-long program will measure soil gas Rn and Hg at sites over the active silicic Rabaul Caldera in Papua New Guinea, in order to test a model developed at Long Valley, California and the Phlegrean Fields, Italy. Rabaul has erupted catastrophically several times in the last 3,500 years, and seismic evidence strongly suggested a major eruption in 1983. This did not take place but the potential is still there and the volcano remains a serious threat. Preliminary data, collected by the PIs just before the crisis of 1983, indicated that substantial anomalous concentrations of both gases were related to the center of uplift and caldera boundary faults. Detectors will be placed over the margins of the caldera, as well as under water in Rabaul harbor (inside the caldera). These should provide baseline measurements necessary to establish the usefulness of Rn and Hg emissions as eruption precursers. The local volcano observatory personnel are also very interested in them as an additional tool to be used in their efforts to monitor this specific volcano.
