Volcano spreading controlled by dipping substrata

Structural analysis of the early stages of catastrophic stratovolcano flank-collapse using analogue models

“…For Socompa and Parinacota, gravitational spreading most probably acted in one preferential direction due to the buttress effect exerted by neighbouring topography, as seen in analogue models by Merle and Borgia (1996). Conversely, Las Isletas-Mombacho is not buttressed by neighbouring topography but is placed on a slightly dipping substratum which, in addition with regional tectonics, probably controlled the direction of collapse Wooller et al 2004). However, in these three volcanosubstratum systems the evidence of gravitational spreading, like radial transtensional grabens in the flanks and summit, or thrust-fold belts at volcano foot, are not as marked as in other spreading volcanoes like Etna or Kilauea (Borgia et al 1992;Morgan et al 2003).…”

“…Major structures observed in other natural examples like Etna and Kilauea (Borgia et al 1992;Morgan et al 2003) as well as in analogue models (Merle and Borgia 1996;Wooller et al 2004;Delcamp et al 2008) suggest that, since the beginning of gravitational spreading, the substratum is dissected in segments that can have an arcuate thrust-fold front (variable α) and a roughly triangular shape (variable d/R). For Socompa and Parinacota, gravitational spreading most probably acted in one preferential direction due to the buttress effect exerted by neighbouring topography, as seen in analogue models by Merle and Borgia (1996).…”

“…Various numerical and analogue models, as well as natural examples, have been used to test the relevance of these parameters (e.g. Merle and Borgia 1996;van Wyk de Vries and Matela 1998;Wooller et al 2004;Delcamp et al 2008).…”

Relationships between volcano gravitational spreading and magma intrusion

“…This mechanism has been widely studied on the field (van Bemmelen 1949; Borgia et al 1992Borgia et al , 2000Borgia and van Wyk de Vries 2003) and using analogue and numerical modelling (Merle and Borgia 1996;van Wyk and Matela 1998;Walter et al 2006;Münn et al 2006;Wooller et al 2004;Morgan and McGovern 2005;Delcamp et al 2008). Grabens, en échelon faults, folds and thrusts are the characteristic spreading-related structures.…”

Late-Pleistocene flank collapse triggered by dome growth at Tacaná volcano, México-Guatemala, and its relationship to the regional stress regime

“…Siebert (1984) concluded that failure of semiconical volcanoes takes place perpendicular to the maximum principal stress in the region. Analogue models have been used to predict the failure of volcanic edifices affected by different types of faults beneath volcanoes, such as a vertical fault (Vidal and Merle 2000;Merle et al 2001), strike-slip faults (van Wyk de Vries and Merle 1998;Lagmay et al 2000); and dipping substrata (Wooller et al 2004). The analogue models suggest that deeper and wider collapses are related to basal spreading, while shallow and narrow collapses are associated with summit growth and injection of new magma (Acocella 2005; and references therein).…”