Paroxysmal dome explosion during the Merapi 2010 eruption: Processes and facies relationships of associated high-energy pyroclastic density currents

Chapter 10 The effect of topography on ash-cloud surge generation and propagation

“…Ash-cloud surges are known to detach and overrun dense basal avalanches after traversing a break in slope, as at Mount Ngauruhoe, New Zealand (Nairn & Self 1978), Santiaguito Volcano, Guatemala (Rose et al 1977), and Merapi (Bourdier & Abdurachman 2001;Lube et al 2011;Jenkins et al 2013). Surges may separate from valley-confined flows when steep topography or barriers are encountered, as was (Charbonnier & Gertisser 2011;Lube et al 2011;Charbonnier et al 2013;Jenkins et al 2013;Komorowski et al 2013). Ashcloud surges have also been known to overspill narrow channels, especially around valley bends, as at Merapi (Bourdier & Abdurachman 2001;Charbonnier & Gertisser 2008Lube et al 2011;Charbonnier et al 2013;Jenkins et al 2013;Komorowski et al 2013), Unzen (Yamamoto et al 1993;Fujii & Nakada 1999) and SHV (Loughlin et al 2002b).…”

“…A number of field studies investigate the morphology and granulometry of single events in great detail (e.g. Loughlin et al 2002b;Charbonnier & Gertisser 2008;Komorowski et al 2010;Lube et al 2011;Komorowski et al 2013), but few aggregate many events in order to extract general information and investigate similarities and differences between PDCs. Complex field relationships that result from the spatial and temporal variability of PDCs need to be reliably distilled in order to understand key physical processes which apply generically and which can be incorporated into dense-dilute coupled models.…”

Syn-eruptive, soft-sediment deformation of deposits from dilute pyroclastic density current: triggers from granular shear, dynamic pore pressure, ballistic impacts and shock waves

“…1a-b). Komorowski et al (2013) interpreted similar features in the deposits of the Merapi 2010 block and ash flows as small degassing pipes related to rapidly deposited and fluidized flows. Here, the dark mLA layer is interpreted as fluidized and overpressurized in dynamic pore pressure during flow in order to explain the basal potatoids and intrusions as injection features.…”

“…Fluid escape SSD (dikes, pipes, plumes, pillars) can occur by escape of water accompanying phreatomagmatic eruptions (Nocita, 1988, -later reinterpreted as water-escape in fluvial deposits by McPherson et al (1989)), degassing of fresh pyroclasts (Gernon et al, 2008(Gernon et al, , 2009, burning underlying vegetation, or be due to thermal expansion (Branney and Kokelaar, 2002, p. 61-66, and references therein). Interestingly, the high deposition rates combined with possible fluidized state of the flow can trap gases in the deposits that subsequently escape as degassing pipes within seconds after deposition (Komorowski et al, 2013). These can occur as fines-depleted pipes, a few centimeters in length and diameter (Pistolesi et al, 2011;Smith and Kokelaar, 2013), or large decimeter-meter scale depressions at the surface of deposits (Charbonnier and Gertisser, 2008).…”

Magmatic gas percolation through the old lava dome of El Misti volcano

“…Mellors et al, 1988) and Merapi (Indonesia; e.g. Komorowski et al, 2013). Critical in determining whether or not an otherwise gravitationally stable dome will become overpressured and collapse is the nature of magmatic outgassing through either the conduit wall or fracture networks (e.g.…”