Journal of Volcanology and Geothermal Research 330 (2017) 43–55 Contents lists available at ScienceDirect Journal of Volcanology and Geothermal Research journal homepage: www.elsevier.com/locate/jvolgeores Video monitoring reveals pulsating vents and propagation path of fissure eruption during the March 2011 Pu'u 'Ō'ō eruption, Kilauea volcano Tanja Witt ⁎,ThomasR.Walter GFZ German Research Centre for Geosciences, Section 2.1: Physics of Earthquakes and Volcanoes, Telegrafenberg, 14473 Potsdam, Germany article info abstract Article history: Lava fountains are a common eruptive feature of basaltic volcanoes. Many lava fountains result from fissure erup- Received 12 April 2016 tions and are associated with the alignment of active vents and rising gas bubbles in the conduit. Visual reports Received in revised form 18 November 2016 suggest that lava fountain pulses may occur in chorus at adjacent vents. The mechanisms behind such a chorus of Accepted 18 November 2016 lava fountains and the underlying processes are, however, not fully understood. Available online 5 December 2016 The March 2011 eruption at Pu'u 'Ō'ō (Kilauea volcano) was an exceptional fissure eruption that was well mon- fi fi Keywords: itored and could be closely approached by eld geologists. The ssure eruption occurred along groups of individ- Kilauea volcano ual vents aligned above the feeding dyke. We investigate video data acquired during the early stages of the Fissure eruption eruption to measure the height, width and velocity of the ejecta leaving eight vents. Using a Sobel edge-detection Vent migration algorithm, the activity level of the lava fountains at the vents was determined, revealing a similarity in the erup- Bubbling magma tion height and frequency. Based on this lava fountain time series, we estimate the direction and degree of cor- Video monitoring relation between the different vents. We find that the height and velocity of the eruptions display a small but systematic shift in time along the vents, indicating a lateral migration of lava fountaining at a rate of ~11 m/s from W to E. This finding is in agreement with a propagation model of a pressure wave originating at the Kilauea volcano and propagating through the dyke at ~10 m/s from W to E. Based on this approach from videos only 30 s long, we are able to obtain indirect constraints on the physical dyke parameters, with important implications for lateral magma flow processes at depth. This work shows that the recording and analysis of video data provide important constraints on the mechanisms of lava fountain pulses. Even though the video sequence is short, it al- lows for the confirmation of the magma propagation direction and a first-order estimation of the dyke dimensions. © 2016 Elsevier B.V. All rights reserved. 1. Introduction member mechanisms of these lateral and eccentric fissures are (i) hor- izontal dyke propagation or (ii) divergence of a magma path at great Fissure eruptions have been observed at Hekla (1947, 1970), Askja depth followed by predominantly vertical dyke ascent. Distinguishing (1961), Mauna Loa (1984), Kilauea (1983–2015, continuing), Dabbahu between these two mechanisms is often difficult (Acocella and Neri, (2005), Reunion (2006), Tolbachik (2013), and many other volcanoes 2003), which is why observation of a lateral-flow mechanism is so im- in past decades (Global Volcanism Project, 2016; Siebert et al., 2011). portant to understanding the link between fissure eruptions and their Commonly referred to as “Hawaiian-type eruptions”, they are predom- source region. inant on ocean islands and at divergent plate margins but also occur at Here, we demonstrate the utility of video monitoring in the study convergent margins and in intraplate settings (Valentine and Gregg, of fissure eruptions. We consider an exceptionally well-monitored 2008). Fissure eruptions can occur kilometers away from the volcano case example of a fissure eruption that occurred at Kilauea, Hawaii summit to which they are connected via crustal flow paths rather than (Poland, 2014). In March 2011, a fissureeruptionoccurredinthe forming a continuous fissure at the surface. At Mauna Loa (Hawaii), fis- East Rift Zone of Kilauea and was located at a distance of over sure eruptions have opened at distances exceeding 15 km from the vol- 17 km from the Kilauea summit crater (Orr et al., 2013a). Specifically, cano summit (Lockwood et al., 1985). The location of a fissure interacts the eruption occurred along several aligned vents, which followed the with the crustal stress field (Walter and Amelung, 2006). At Etna volca- surface expression of a geodetically and seismically inferred dyke intru- no (Italy), fissure eruptions may occur close to inhabited areas on the sion (Lundgren et al., 2013). A lateral magma flow is geometrically hy- lower slope of the volcanic edifice (Acocella and Neri, 2009). The end- pothesized because the eruption vents formed at a significant lateral distance from Kilauea (Lundgren et al., 2013). Additionally, fluctuations ⁎ Corresponding author. in the lava lake level at Kilauea were coincident with activity changes at E-mail address: [email protected] (T. Witt). Pu'u 'Ō'ō (Poland, 2014), suggesting a hydraulic connection (Montagna http://dx.doi.org/10.1016/j.jvolgeores.2016.11.012 0377-0273/© 2016 Elsevier B.V. All rights reserved. 44 T. Witt, T.R. Walter / Journal of Volcanology and Geothermal Research 330 (2017) 43–55 and Gonnermann, 2013). However, to date, no direct observations have of magmatic gas, magma and pyroclastic products. The height of a foun- tested or quantified the lateral magma flow concept based on vent ac- tain can reach hundreds of meters. The dynamics of lava fountains may tivity at an erupting fissure. Because fissures open sequentially and be governed by gas bubble layers that either form during magma rise or show venting activity that appears to be correlated to those fissures previously accumulate at depth and drive the intensity of the eruption (Björnsson, 1985; Jackson et al., 1975; Mangan et al., 1995), lateral (Allard et al., 2005; Manga, 1996). So far, this description has considered magma propagation may continue to dominate the subterranean only the vertical dynamics, but fissure eruptions represent structures system. with a considerable horizontal extent. Therefore, we attempt here to in- The pulsating behaviour of vents can be investigated in detail via vestigate the horizontal dynamics as well. video analysis, as this study shows. Video analyses have been per- formed elsewhere to investigate volcanic processes because camera 2.1. Hawaiian lava fountains and venting activity monitoring facilitates continuous footage at reasonable costs and in high resolution (Diefenbach et al., 2011; Walter, 2011). This moni- The classic type of lava fountaining can be regularly observed on Ha- toring technique is flexible over a wide range of time scales and al- waii and is therefore often referred to as “Hawaiian type”.Highlyener- lows both a broad spatial coverage and a precise measurement of getic fountain pulses can reach heights of up to 1500 m (Allard et al., local surface processes (e.g., Bluth and Rose, 2004; Honda and 2005). Lava fountains are thought to be caused by the rise of a mixture Nagai, 2002). However, for many applications, it has a lower preci- of gas bubbles and low-viscosity magma to the surface (Parfitt, 2004). sion than ground-based surveying techniques (Diefenbach et al., The gas bubbles may be formed at different depths due to volumetric 2011). The methods used for video monitoring are separated into expansion of volatiles and may be trapped in storage regions prior to satellite-, aerial- and terrestrial-based methods (Walter et al., eruption. 2013), in which quantitative image analysis, digital flow-field com- Different conceptual models of lava fountain dynamics suggest putation, image sequence matching and other photogrammetric different gas compositions (proportion of CO2 or H2O), formation and computer vision algorithms are applied (e.g., Baldi et al., 2000; mechanisms and bubble accumulation zones (Parfitt, 2004). The James et al., 2007; James et al., 2006; Julio Miranda and Delgado collapsing foam model (CF, e.g., Jaupart and Vergniolle, 1988; Granados, 2003). Common applications in volcanology have includ- Jaupart and Vergniolle, 1989; Vergniolle and Jaupart, 1986; ed the study of deforming craters (Patrick et al., 2010), extrusion Vergniolle and Jaupart, 1990; Vergniolle and Mangan, 2000)as- (Major et al., 2009) and collapse of lava domes (Walter, 2011), sumes that CO2 is the driving gas. Between the conduit and the changes in the volcanic topography (Cecchi et al., 2003), deforma- magma storage zone, bubbles form and become trapped. The bub- tion patterns, displacement vectors (Major et al., 2009) and other bles accumulate as a foam (Parfitt, 2004)oralayerofgas(Allard physical parameters, such as ejection velocities of pyroclasts et al., 2005)atasignificant depth, as much as 1.5 km beneath the (Taddeucci et al., 2012a; Taddeucci et al., 2012b). Using thermal surface. Some bubbles collapse, coalesce or ascend as an annular cameras a lava flow flux variations (James et al., 2007), cyclic rising two-phase flow of gas and melt through the conduit, with the two and falling of a lava lake surface during unrest (Spampinato et al., phases exhibiting significantly different flow velocities. The erup- 2013), dome building (Schneider et al., 2008), fumarole activity tion style depends on whether the foam is collapsing instanta- (Stevenson and Varley, 2008) and many other volcanic