Abstract
Rootless cones form when partially outgassed lava interacts explosively with external water. The explosions represent an end-member system that can elucidate mechanisms of explosive magma–water interactions in the absence of magmatic fragmentation induced by outgassing. The proportion of finely fragmented ejecta (i.e., ash), generated in rootless explosions, may contribute significantly to the energy of the explosion even if the ash volume is small relative to coarser ejecta. Laboratory experiments indicate that the degree of melt–water mixing and energy release are proportional to the abundance of blocky grains, fragmented by brittle disintegration, which effectively contribute thermal energy to the system. To constrain the mechanisms and dynamics of rootless explosive activity, we assess the nature and modes of fragmentation and ejecta characteristics through morphological, textural, and density analysis of rootless tephra associated with a pāhoehoe lava flow in a lacustrine (lake basin) environment. We observe strong correlations between the mean grain size and the mass percentage of both blocky (negative power law trend) and fluidal (positive logarithmic) tephra clasts of all sizes. We interpret these trends as scale-dependent fragmentation behavior due to the decreasing efficacy of hydrodynamic fragmentation as it occurs over finer scales, especially over the ash size range. Additionally, all analyzed beds contain fine ash-sized blocky and mossy clasts, which are thought to be diagnostic of a high transfer rate of thermal to mechanical energy, characteristic of molten fuel–coolant interactions. These results agree with a recent model of rootless cone formation, prior fragmentation theory, and scaled laboratory experiments and therefore provide a field-based analog for future experimental and modeling efforts.
Similar content being viewed by others
References
Belousov A, Behncke B, Belousova M (2011) Generation of pyroclastic flows by explosive interaction of lava flows with ice/water-saturated substrate. J Volcanol Geotherm Res 202(1):60–72
Büttner R, Dellino P, La Volpe L, Lorenz V, Zimanowski B (2002) Thermohydraulic explosions in phreatomagmatic eruptions as evidenced by the comparison between pyroclasts and products from molten fuel coolant interaction experiments. J Geophys Res: Solid Earth 107(B11):ECV 5-1–ECV 5-14
Büttner R, Dellino P, Zimanowski B (1999) Identifying magma-water interaction from the surface features of ash particles. Nature 401(6754):688–690
Büttner R, Zimanowski B (1998) Physics of thermohydraulic explosions. Phys Rev E 57(5):5726–5729
Carey RJ, Manga M, Degruyter W, Swanson D, Houghton B, Orr T, Patrick M (2012) Externally triggered renewed bubble nucleation in basaltic magma: the 12 October 2008 eruption at Halema‘uma‘u overlook vent, Kīlauea, Hawai‘i, USA. J Geophys Res: Solid Earth 117(B11202)
Cashman KV, Mangan MT, Newman S (1994) Surface degassing and modifications to vesicle size distributions in active basalt flows. J Volcanol Geotherm Res 61(1):45–68
Dellino P, Frazzetta G, La Volpe L (1990) Wet surge deposits at La Fossa di Vulcano: depositional and eruptive mechanisms. J Volcanol Geotherm Res 43(1):215–233
Dellino P, Isaia R, La Volpe L, Orsi G (2001) Statistical analysis of textural data from complex pyroclastic sequences: implications for fragmentation processes of the Agnano-Monte spina tephra (4.1 ka), Phlegraean fields, southern Italy. Bull Volcanol 63(7):443–461
Dellino P, La Volpe L (1995) Fragmentation versus transportation mechanisms in the pyroclastic sequence of Monte Pilato-Rocche Rosse (Lipari, Italy). J Volcanol Geotherm Res 64(3–4):211–231
Edwards BR, Karson J, Wysocki R, Lev E, Bindeman I, Kueppers U (2013) Insights on lava–ice/snow interactions from large-scale basaltic melt experiments. Geology 41(8):851–854
Fagents SA, Thordarson T (2007) Rootless volcanic cones in Iceland and on Mars. In: Chapman MG (ed) The geology of Mars: evidence from earth-based analog. Cambridge University Press, United Kingdom, pp. 151–177
Fisher RV (1968) Puu Hou littoral cones, Hawaii. Geol Rundsch 57(3):837–864
Gaonac’h H, Stix J, Lovejoy S (1996) Scaling effects on vesicle shape, size and heterogeneity of lavas from Mount Etna. J Volcanol Geotherm Res 74(1):131–153
Greeley R, Fagents SA (2001) Icelandic pseudocraters as analogs to some volcanic cones on Mars. J Geophys Res: Planets 106(E9):20527–20546
Gualda GA, Ghiorso MS, Lemons RV, Carley TL (2012) Rhyolite-MELTS: a modified calibration of MELTS optimized for silica-rich, fluid-bearing magmatic systems. J Petrol 53(5):875–890
Hamilton CW, Fitch EF, Fagents SA, Thordarson T (2017) Rootless tephra stratigraphy and emplacement processes. Bull Volcanol doi:10.1007/s00445-016-1086-4
Heiken G (1972) Morphology and petrography of volcanic ashes. Geol Soc Am Bull 83(7):1961–1988
Heiken G (1974) An atlas of volcanic ash. Smithsonian Institution Press, Washington, DC
Heiken G, Wohletz K (1985) Volcanic ash. University Press, California, Chicago, Harvard & MIT
Herd RA, Pinkerton H (1997) Bubble coalescence in basaltic lava: its impact on the evolution of bubble populations. J Volcanol Geotherm Res 75(1–2):137–157
Houghton B, Hackett W (1984) Strombolian and phreatomagmatic deposits of Ohakune craters, Ruapehu, New Zealand: a complex interaction between external water and rising basaltic magma. J Volcanol Geotherm Res 21(3):207–231
Houghton B, Schmincke H (1986) Mixed deposits of simultaneous strombolian and phreatomagmatic volcanism: Rothenberg volcano, east Eifel volcanic field. J Volcanol Geotherm Res 30(1):117–130
Houghton B, Smith R (1993) Recycling of magmatic clasts during explosive eruptions: estimating the true juvenile content of phreatomagmatic volcanic deposits. Bull Volcanol 55(6):414–420
Houghton B, Wilson C (1989) A vesicularity index for pyroclastic deposits. Bull Volcanol 51(6):451–462
Mangan MT, Cashman KV (1996) The structure of basaltic scoria and reticulite and inferences for vesiculation, foam formation, and fragmentation in lava fountains. J Volcanol Geotherm Res 73(1):1–18
Mattox TN, Mangan MT (1997) Littoral hydrovolcanic explosions: a case study of lava–seawater interaction at Kilauea volcano. J Volcanol Geotherm Res 75(1–2):1–17
Morrissey M, Zimanowski B, Wohletz K, Buettner R (2000) Phreatomagmatic fragmentation. In: Houghton B, Rymer H, Stix J, McNutt S (eds) Encyclopedia of volcanoes. Academic Press, San Diego, pp. 431–445
Patel A, Manga M, Carey RJ, Degruyter W (2013) Effects of thermal quenching on mechanical properties of pyroclasts. J Volcanol Geotherm Res 258:24–30
Polacci M, Burton MR, La Spina A, Murè F, Favretto S, Zanini F (2009) The role of syn-eruptive vesiculation on explosive basaltic activity at Mt. Etna, Italy. J Volcanol Geotherm Res 179(3):265–269
Reynolds P, Brown RJ, Thordarson T, Llewellin EW, Fielding K (2015) Rootless cone eruption processes informed by dissected tephra deposits and conduits. Bull Volcanol 77(9):1–17
Robert B, Harris A, Gurioli L, Médard E, Sehlke A, Whittington A (2014) Textural and rheological evolution of basalt flowing down a lava channel. Bull Volcanol 76(6):1–21
Sinton J, Grönvold K, Sæmundsson K (2005) Postglacial eruptive history of the western volcanic zone, Iceland. Geochem Geophys Geosyst 6(12)
Stovall WK, Houghton B, Gonnermann H, Fagents S, Swanson D (2011) Eruption dynamics of Hawaiian-style fountains: the case study of episode 1 of the Kīlauea Iki 1959 eruption. Bull Volcanol 73(5):511–529
Stovall WK, Houghton BF, Hammer JE, Fagents SA, Swanson DA (2012) Vesiculation of high fountaining Hawaiian eruptions: episodes 15 and 16 of 1959 Kīlauea Iki. Bull Volcanol 74(2):441–455
Thorarinsson S (1951) Laxárgljúfur and Laxárhraun: a tephrochronological study. Geogr Ann 33:1–89
Thorarinsson S (1953) The crater groups in Iceland. Bull Volcanol 14(1):3–44
Thordarson T, Höskuldsson A (2002) Classic geology in Europe 3. Terra Publishing, Harpenden
von Komorowicz M (1912) Vulkanologische studien auf einigen inseln des Atlantischen Oceans. E. Schweizerbart, Stuttgart
Walker G, Croasdale R (1971) Characteristics of some basaltic pyroclastics. Bull Volcanol 35(2):303–317
Wilmoth RA, Walker GP (1993) P-type and S-type pahoehoe: a study of vesicle distribution patterns in Hawaiian lava flows. J Volcanol Geotherm Res 55(1):129–142
Wohletz K, McQueen R (1981) Experimental hydromagmatic volcanism. Amer Geophys.Union trans Eos 62(45):1085
Wohletz K, McQueen R (1984) Volcanic and stratospheric dustlike particles produced by experimental water-melt interactions. Geology 12(10):591–594
Wohletz KH (1983) Mechanisms of hydrovolcanic pyroclast formation: grain-size, scanning electron microscopy, and experimental studies. J Volcanol Geotherm Res 17(1–4):31–63
Wohletz KH (1986) Explosive magma-water interactions: thermodynamics, explosion mechanisms, and field studies. Bull Volcanol 48(5):245–264
Wohletz KH, Zimanowski B, Büttner R (2013) Magma-water interactions. In: Fagents SA, Gregg TKP, Lopes RMC (eds) Modeling volcanic processes. Cambridge University Press, New York, pp. 230–257
Zimanowski B (2001) Phreatomagmatic explosions. In: Freundt A, Rosi M (eds) From magma to tephra: modeling physical processes of explosive volcanic eruptions, developments in volcanology 4. Elsevier Science B.V, Amsterdam, pp. 25–54
Zimanowski B, Büttner R, Lorenz V, Häfele H-G (1997) Fragmentation of basaltic melt in the course of explosive volcanism. J Geophys Res: Solid Earth 102(B1):803–814
Zimanowski B, Wohletz K, Dellino P, Büttner R (2003) The volcanic ash problem. J Volcanol Geotherm Res 122(1):1–5
Acknowledgements
We would like to thank the Icelandic Institute of Natural History for generous access to the study area. We are grateful to Gary Huss, Ryan Ogliore, Aurelien Thomen, Elizabeth Koeman, and Myriam Telus at the Hawai‘i Institute of Geophysics and Planetology for help with sample preparation and assistance with SEM and EDS analysis. We also thank Bruce Houghton, Scott Rowland, John Sinton, Maria Janebo, and Samantha Isgett at the University of Hawai‘i Department of Geology and Geophysics for helpful discussions. This work was supported by NSF EAR-1119648 HIGP publication number 2240 and SOEST publication number 9876.
Author information
Authors and Affiliations
Corresponding author
Additional information
Editorial responsibility: R.J. Brown
Electronic supplementary material
ESM 1
(PDF 942 kb)
Rights and permissions
About this article
Cite this article
Fitch, E.P., Fagents, S.A., Thordarson, T. et al. Fragmentation mechanisms associated with explosive lava–water interactions in a lacustrine environment. Bull Volcanol 79, 12 (2017). https://doi.org/10.1007/s00445-016-1087-3
Received:
Accepted:
Published:
DOI: https://doi.org/10.1007/s00445-016-1087-3