Short Term Variation in Mass Flux During Basaltic Eruptions

University Of Hawaii, Honolulu

Investigators

Abstract

Harris and Flynn EAR-0106349 Mass flux rates have been shown to vary over day-to-month long periods during effusive basaltic eruptions. These variations provide insights into eruption mechanisms, revealing whether or not the chamber was pressurized. Little data exist, however, to determine how mass fluxes vary over time scales of seconds to hours. Such data would provide insight into the variability of supply during an eruption. Over recent years unpublished data have been gathered indicating that erupted mass fluxes may vary between high and low levels over minute-long periods. If such short term cyclicity exists, then this finding will provide unique insights into the stability of supply to persistent basaltic eruptions over minute to hour long periods. The objective of this research is thus to search for and examine short term mass flux variations during ongoing basaltic eruptions defining, for the first time, any cyclicity in the short term mass flux that may exist. This will provide us insights into the supply mechanism during persistent effusive eruptions, answering the prime question: is supply steady or surging? This in turn will allow us to apply conduit convection models that explain the relevant supply mode. To achieve these objectives, two volcanoes characterized by contrasting styles of persistent activity have been selected for analysis: Kilauea (Hawai'i) and Villarrica (Chile). While activity at Kilauea is dominated by the emplacement of tube-fed lava flows, Villarrica hosts a persistently active lava lake. At both of these volcanoes, preliminary data indicate that magma supply to the eruption site may cycle between high and low levels, with each cycle lasting minutes to hours. At each volcano data sets capable of revealing short term mass flux variation will be collected. At Kilauea, thermal measurements will be made every 1-2 seconds at skylights along the active master tube and at incandescent vents over the eruption site. At Villarrica, during two field campaigns, thermal data will be collected simultaneously with gas flux and seismic data. Results will be correlated and analyzed for evidence of cyclic supply to Villarrica's lava lake. At both targets, satellite thermal data collected on a daily basis will be used to construct longer mass flux time series allowing the persistence of any cyclic behavior to be examined. These data sets of multiple geophysical measurements will allow conduit convection and degassing models to be fitted to each system. This research will advance our scientific understanding of persistently erupting systems by extending knowledge of how volcanic eruptions evolve over short time periods. We will also assess the validity of popular gas-based conduit convection models that predict and explain such short term variation in terms of variable volatile content and/or convective overturn. We will use these data to support educational/outreach projects in 3 ways. (1) We will make the data available on the Internet for public access. (2) We will use these data to support University of Hawai'i courses for teachers, allowing them to develop exciting high school lesson plans using real-time data. (3) Through the support of Hawai'i Space Grant Consortium undergraduate students will benefit by using the data to support their work.