Advances in studies of dense volcanic granular flows

Abstract

The collapse and decrepitation of a lava dome at the summit of a volcano generally results in the generation of dense granular flows, often referred to as block and ash flows. As the dome particles propagate from the source, they break apart by internal pressure as well as collision. The propagation of block and ash flows can be simulated to some accuracy with a depth averaged numerical model of the equations of continuity and momentum for a material with a frictional resistance. However, important features of such flows, such as the influence of remote stress through force chains, erosion of the volcano substrate, and shock formation and pressurization upon particle break up are poorly understood. In the near future, the influence of these factors will be incorporated into depth averaged models. Various numerical techniques based on particles will some day yield results that can be compared not only with bulk flow properties, but to the internal layering of block and ash flow deposits.

Aplicación de modelos numéricos de "aguas someras" para el análisis de peligros de flujos volcánicos: El caso de Titan2D y volcán Turrialba (Costa Rica)

“…Titan2D has been applied to and evaluated against small-scale pyroclastic flows, block-andash flows and rock avalanches, including those at Colima Volcano, Mexico Saucedo et al, 2005;Rupp et al, 2006;Capra et al 2011), El Misti, Peru (Delaite et al, 2005) and Little Tahoma Peak, Washington, USA (Stinton et al, 2004;Sheridan et al, 2005). The outcomes of these studies have highlighted the uncertainties in objectively defining model input parameters for realistic simulation of local flow conditions.…”

“…Applications of these models have been used for block-andash flows at several volcanoes including Colima, El Chichon and Nevado de Toluca volcanoes in Mexico Patra et al, 2005;Saucedo et al, 2005;Rupp et al, 2006;Macias et al, 2008;Sulpizio et al, 2010); Mount Taranaki, New Zealand (Procter et al, 2010); Tungurahua, Ecuador (Kelfoun et al, 2009); Galeras and El Chichon Volcano, Columbia (Stefanescu et al, 2009;Murcia et al, 2010); Arenal Volcano, Costa Rica (Berrocal & Malavassi, 2006); Soufrière Hills Volcano, Montserrat (Hidayat et al, 2007;Ogburn, 2008;Ogburn et al, in press); and Merapi Volcano, Indonesia (Itoh, 2000;Charbonnier & Gertisser, 2009, 2012.…”

Digital elevation model uncertainty and hazard analysis using a geophysical flow model

“…The governing equations are obtained by applying conservation laws to the incompressible continuum, providing appropriate constitutive modelling assumptions, and then taking advantage of the shallowness of the flows (flows are much longer and wider than they are deep) to obtain simpler depth-averaged representations (Bursik et al 2005). The motion of the material is considered to be gravitationally driven and resisted by both internal and bed friction.…”

Numerical simulations of block-and-ash flows using the Titan2D flow model: examples from the 2006 eruption of Merapi Volcano, Java, Indonesia

“…This has highlighted the unpredictable and poorly understood behaviour of Merapi's flows and the urgent need for improved and reliable geophysical mass flow models to better assess the potential hazard of such flows. Despite the fact that BAFs are amongst the most dangerous volcanic phenomena, only a small number of realistic numerical simulations of actual events over accurate 3-D terrain, using various computational models, have been published (e.g., Wadge et al 1998;Itoh et al 2000;Pitman et al 2003;Sheridan et al 2004;Bursik et al 2005;Saucedo et al 2005;Rupp et al 2006;Macías et al 2008;Widiwijayanti et al 2008). The aims of this paper are to apply the Titan2D flow model to simulate well-characterized BAFs from the 2006 eruption of Merapi (Charbonnier and Gertisser 2008) and to define key flow parameters that will allow more reliable predictions of the areas and levels of hazards associated with BAFs during future eruptions at Merapi.…”