Three Years of Ground-based Thermal Monitoring at Kilauea

Three permanent ground-based infrared (8 to 14 micron) radiometers, located on Pu'u 'O'o's north crater rim, have provided continuous real-time monitoring of activity within Pu'u 'O'o since March 2001. Our thermal sensors are able to detect lava flows, catastrophic changes in crater floor morphology, and variations in the style and vigor of volcanic degassing. These continuous, long-term thermal observations, integrated with RSAM and tilt measurements, provide an opportunity to investigate the changing nature of systemic activity at Kilauea. For example, our thermal sensors are able to detect periods of lava effusion on the crater floor, coincident with the termination of the rootless shield to the east and subsequent back-up into Pu'u O'o, before activity transitioned to the Mother's Day flow field. Since June 2001, at least one radiometer has been continuously aimed at the central pit vent of Pu'u O'o, whose thermal record has been dominated by regular gas jetting events, typically referred to as gas pistoning. These events are very often observed in the thermal records, indicating that they are a dominant mode of degassing at Kilauea. During June and July of 2000, gas pistoning from the central pit vent occurred with fundamental recurrence intervals of about 2 to 10 minutes, but since October has slowed to less frequent 20 to 40 minute intervals. We propose that the variation in piston frequency is related to dramatic changes in the geometry of the underground plumbing system at Pu'u 'O'o. Currently thermal monitoring of two individual vents, which are separated by ~100 m, provides evidence for linked degassing, further demonstrating the complex and ephemeral nature of the plumbing system beneath Pu'u 'O'o's crater floor.