Improved identification of volcanic features using Landsat 7 ETM+

Volcanic eruptions can present unpredictable hazards to populations living within regions containing potentially active volcanoes and for people traveling in jet aircraft that intersect with ash-laden eruption clouds. Methods of monitoring volcanic activity include searching for variations in the thermal signal from active fumaroles, lava domes, lava lakes, flows, and other features. Over many active volcanoes in the Western Hemisphere, low spatial resolution (4 km/pixel) weather satellite data acquired every 15 min are used to identify changes in eruptive activity, but are of insufficient spatial resolution to map active volcanic features. The Enhanced Thematic Mapper Plus (ETM+) on Landsat 7 can be used to monitor active volcanoes at a higher spatial resolution (15- to 60-m pixels). ETM+ also offers improvements over its predecessor, the Thematic Mapper of Landsats 4 and 5, by way of a 15-m panchromatic band and higher spatial resolution (60 m/pixel) thermal infrared (IR) band. With higher spatial resolution panchromatic data, we are able to map lava flow fields, trace very high temperature lava channels, and, at Lascar volcano, identify an arcuate feature associated with a collapsed crater floor, a phenomenon that may precede explosive activity. With improved spatial resolution in the thermal IR, we are able to map the bifurcation and braiding of underground lava tubes at Kilauea. Identifying tube locations and tracking their extension are important because, for a given volumetric lava production (effusion) rate, tube-fed flows can extend a much greater distance than surface flows. At both Kilauea and Etna, we are able to use the thermal data to estimate effusion rates, an important parameter for assessing how far a flow is likely to extend and therefore the hazard it poses. An improved ETM+ data collection and distribution system includes a well-formulated and -executed Long-Term Acquisition Plan and less expensive data that is available much faster than previously possible.