Eruption dynamics of Hawaiian-style fountains: the case study of episode 1 of the Kīlauea Iki 1959 eruption

Abstract

Hawaiian eruptions are characterized by fountains of gas and ejecta, sustained for hours to days that reach tens to hundreds of meters in height. Quantitative analysis of the pyroclastic products from the 1959 eruption of Kīlauea Iki, Kīlauea volcano, Hawai'i, provides insights into the processes occurring during typical Hawaiian fountaining activity. This short-lived but powerful eruption contained 17 fountaining episodes and produced a cone and tephra blanket as well as a lava lake that interacted with the vent and fountain during all but the first episode of the eruption, the focus of this paper. Microtextural analysis of Hawaiian fountaining products from this opening episode is used to infer vesiculation processes within the fountain and shallow conduit. Vesicle number densities for all clasts are high (10 6 -10 7 cm −3 ). Post-fragmentation expansion of bubbles within the thermally-insulated fountain overprints the pre-fragmentation bubble populations, leading to a reduction in vesicle number density and increase in mean vesicle size. However, early quenched rims of some clasts, with vesicle number densities approaching 10 7 cm −3 , are probably a valid approximation to magma conditions near fragmentation. The extent of clast evolution from low vesicle-to-melt ratio and corresponding high vesicle number density to higher vesicle-to-melt ratio and lower vesicle-number density corresponds to the length of residence time within the fountain.

Magma decompression rates during explosive eruptions of Kīlauea volcano, Hawaii, recorded by melt embayments

“…Our results provide the first constraints from Hawai'i with which to develop dynamic conduit flow models, and to test inferences from the textural analysis of eruption deposits (e.g. Mangan and Cashman, 1996;Stovall et al, 2011) for how decompression rate influences volatile exsolution and magma fragmentation. Table 2.…”

“…We chose the first episode of the 1959 eruption because subsequent phases were affected by the drain-back of degassed lava into the conduit (Wallace and Anderson, 1998;Sides et al, 2014a). Our samples are taken from layer ρ17 of Stovall et al (2011). (2) The Keanakāko'i basal reticulite (embayments ReticE1 and ReticE2):…”

Relating vesicle shapes in pyroclasts to eruption styles

“…Vesicle shapes are analyzed using a fixed magnification to ensure the same pixel resolution throughout. Thus, vesicle shapes were analyzed on all the vesicles imaged at a scale of 1 μm/px (×100 magnification) in backscattered electron images from a given thin section, previously used for the study of vesicle size distributions (Tables 2 and 4; Adams et al 2006;Sable et al 2006Sable et al , 2009Lautze and Houghton 2007;Houghton et al 2010;Stovall et al 2011). In these studies, the original, grayscale, SEM images were transformed into binary images using Adobe Photoshop and Scion Image (Scion Corporation, USA) or ImageJ (Schneider et al 2012) software.…”

“…Vesicle shape is another manifestation of magma ascent conditions, in particular bubble growth, coalescence, and shearing (e.g., Klug and Cashman 1996;Mangan and Cashmann 1996;Polacci et al 2003;Rust et al 2003;Okumura et al 2008;Wright and Weinberg 2009), and can therefore provide a valuable complement to conventional studies of pyroclast textures. Volume fraction of crystals in the groundmass Regularity (as defined by Shea et al 2010) (1) Parfitt (2004), (2) Stovall et al (2011), (3) Wallace (1998), (4) Lautze and Houghton (2007), (5) Pistolesi et al (2011), (6) Burgisser et al (2010), (7) Giachetti et al (2010), (8) Druitt et al (2002), (9) Adams et al (2006), (10) Hildreth and Fierstein (2012), (11) Houghton et al (2010), (12) Walker (1980), (13) Dunbar et al (1989), (14) Sable et al (2009), (15) Coltelli et al (1998), (16) Sable et al (2006), (17) Giordano (2003) Here, we study vesicle shapes in pyroclasts from fall deposits of seven explosive eruptions, comprising six different eruptive styles, including the enigmatic Plinian eruptions of basaltic magma, for which the cause for high explosive intensity has been controversial (e.g., Walker et al 1984;Coltelli et al 1998;Houghton et al 2004;Sable et al 2006Sable et al , 2009Costantini et al 2009;Goepfert and Gardner 2010). We are primarily interested in the relationship between bubble growth, as a consequence of magma decompression, and vesicle shape.…”

Caracterización geoquímica de los depósitos alimentados por fuentes de lava del volcán Las Herrerías (Región Volcánica del Campo de Calatrava, Ciudad Real)

“…Stovall et al, 2010). Tales fuentes de lava lanzan al aire piroclastos muy fluidos y calientes (de hasta 1-2 m de diáme-tro) que son emitidos desde el cráter a velocidades de ≈100 m/s y habitualmente ascienden hasta alturas de unas pocas decenas a unos pocos cientos de metros sobre la boca eruptiva antes de caer al suelo (e.g.…”