Influence of the topography of stratovolcanoes on the propagation and channelization of dense pyroclastic density currents analyzed through numerical simulations

Abstract

We applied systematically the branching energy cone model to a large (𝑁 = 50) set of stratovolcanoes around the world in order to evaluate the main topographic characteristics that may control the propagation of dense pyroclastic density currents (PDCs). Results indicate that channelization efficiency of a PDC is strongly controlled by the relative scale between flow size and volcano topographic features. Most of the studied stratovolcanoes topographies are able to induce significant PDC channelization in proximal domains, while strong channelization in distal zones is mainly observed for volcanoes with steep flanks, with long, uninterrupted valleys, and with catchments zones of pyroclastic material (i.e. the valleys heads) located near the source. From the statistical analysis of numerical results, we recognize five groups of stratovolcanoes in terms of the mode of interaction between their topographies and dense PDCs: (1) intense channelization through different valleys up to distal domains (e.g. Colima and Peteroa); (2) intense channelization through a single, dominant valley up to distal domains (e.g. Reventador and Mt. St. Helens); (3) intense channelization near the source and moderate distal channelization, frequently involving intertwined drainage networks (e.g. Tungurahua and El Misti); (4) potentially intense channelization only near the source, typically involving flat distal topographies (e.g. Sinabung and Mayon); and (5) weak channelization in proximal domains, resulting in efficient early energy dissipation and thus reduced PDC run-out distance (e.g. Kelut and Akagi). The relevance of this classification lies on the possibility of defining volcanic analogues (defined here as volcanoes that share a suite of topographic characteristics and may be considered comparable to a certain extent) and identifying the main processes that may affect PDC propagation in specific topographic contexts. These aspects are useful for studying poorly documented volcanic edifices and for volcanic hazard assessment. Additionally, we compare this classification with published morphometric characteristics of volcanoes, showing that morphometric parameters such as mean slope of the low flank, irregularity index, ratio of volcano height and basal width, and ratio of crater width and basal width, are useful variables for recognizing the groups we defined. These parameters can be used as rough indicators of the expected interaction patterns between the topography of a given volcano and dense PDCs.

Topographic Controls on Pyroclastic Density Current Hazard at Aluto Volcano (Ethiopia) Identified Using a Novel Zero‐Censored Gaussian Process Emulator

“…This general effect is compounded by processes like PDC channelization and overbanking, which also depend on flow size and mobility, and topography surrounding the vent location. All this is compatible with previous observations made at several volcanoes worldwide (e.g., Aravena & Roche, 2022; Breard et al., 2023; Charbonnier et al., 2020; Charbonnier & Gertisser, 2012; Gueugneau et al., 2020; Ogburn & Calder, 2017; Ogburn et al., 2014; Tennant et al., 2021; Tierz et al., 2018). Notwithstanding, it is also important to place the PDC modeling developed using TITAN2D into the wider context of what is currently known in terms of PDC dynamics.…”

Probabilistic hazard assessment for pyroclastic density currents at Tungurahua volcano, Ecuador

“…These results indicate that, in addition to the significant difference in the collapsing volumes of ES2 and ES3, the strong differences in the resulting hazard maps are also modulated by a change in the behavior of the simulated PDCs above a threshold of collapsing volume of pyroclasts, which in fact coincides with the transition between the calibrated volumes of pyroclasts of ES2 and ES3. The capacity of the topography of stratovolcanoes to influence the behaviour of PDCs has been recently addressed by Aravena and Roche (2022), who classified Tungurahua volcano as a case of intense proximal channelization and moderate distal channelization based on the analysis of numerical simulations of dense PDCs. This is due to the well-defined radial ravines that favor PDC propagation in proximal domains and pronounced tangential valleys (Puela, Chambo and Pastaza rivers) that buffer the increase of runout distance toward N, NW and NE and of inundation area when PDCs reach the edifice base (i.e.…”

“…This makes even more critical the need to refine our knowledge about large-scale explosive events at Tungurahua volcano. In addition, Aravena and Roche (2022) recognized the clear effect of proximal obstacles in PDC propagation at Tungurahua, which is probably due to the crater topography and the presence of the ~3 ka BP collapse scar that limit the propagation of small-scale PDCs towards NE. Although probabilistic volcanic hazard maps as those presented here integrate a large amount of information that are more or less easily understandable by the vast majority of the volcanological community, they are not directly accessible by local communities and decision makers (see for example Thompson et al 2015).…”

PyroCLAST: a new experimental framework to investigate overspilling of channelized, concentrated pyroclastic currents

“…They exhibit remarkably long flow runouts compared to other geophysical granular flows of similar volume (Dade and Huppert 1998;Druitt, 1998;Calder et al 1999;Iverson and Vallance 2001). Previous studies on CPCs have demonstrated that channelization can enhance flow runout by confining the entire mass into a restricted area, preventing rapid lateral spreading and efficient energy dissipation (Woods et al 1998;Calder et al 1999;Andrews and Manga 2012;Jessop et al 2012;Charbonnier et al 2013;Ogburn et al 2014;Aravena and Roche 2022). Furthermore, a high interstitial gas pore pressure and related fluidization in the concentrated basal layer has been proposed as an efficient mechanism to reduce the inter-particle friction and also enhance flow runout (Sparks 1978;Wilson 1980;Druitt et al 2004;Bareschino et al 2007;Dufek 2016;Lube et al 2020), as demonstrated by numerous experimental works (Druitt et al 2007;Girolami et al, 2015;Roche et al 2010;Rowley et al 2014;Smith et al 2018Smith et al , 2020 and numerical studies (Gueugneau et al 2017;Breard et al 2019Breard et al , 2022Lube et al 2019;Aravena et al 2021).…”