Constraints on the partitioning of Kīlauea’s lavas between surface and tube flows, estimated from infrared satellite data, sulfur dioxide emission rates, and field observations

Abstract

This paper describes how observations of sulfur dioxide (SO2) degassing rates (obtained in situ), thermal emission rates (obtained from infrared satellite data), and semiquantitative flow field observations can be used to elucidate the partitioning of lava between the surface and tube systems at Kīlauea volcano, Hawai’i, over a decadal timescale. For most of our study period, 2000 to 2009, we found that the infrared spectral radiance measured by Moderate Resolution Imaging Spectroradiometer from the flow field under clear-sky conditions is controlled by the lava effusion rate and the amount of flow accommodated by the subsurface tube system. At Kīlauea, the degree of tubing is estimated qualitatively using field observations, and we show that the satellite data and in situ gas data can be used to estimate the percentage of lava on the surface relative to the total amount erupted. This empirical relationship works to describe many cases in the past decade at Kīlauea but breaks down when there is a lack of concurrent clear-sky radiance and SO2 data or when magma is being stored and degassed prior to eruption. Our observations provide a simple way to estimate the partitioning of Kīlauea’s total lava supply between surface and tube-fed flows using a long-term dataset. This is important because the transition between periods when lava is distributed primarily by surface flows to periods where tubes dominate has been suggested to indicate significant changes in the character of decadal-scale eruptions at Kīlauea (Heliker et al., Bull Volcanol 59:381–393, 1998). In addition, it is during those times when surface flows predominate that the flow field does most of its lateral expansion and the hazards associated with the lava effusion become more pronounced.