Shallow magma diversions during explosive diatreme-forming eruptions

Abstract

The diversion of magma is an important mechanism that may lead to the relocation of a volcanic vent. Magma diversion is known to occur during explosive volcanic eruptions generating subterranean excavation and remobilization of country and volcanic rocks. However, feedbacks between explosive crater formation and intrusion processes have not been considered previously, despite their importance for understanding evolving hazards during volcanic eruptions. Here, we apply numerical modeling to test the impacts of excavation and subsequent infilling of diatreme structures on stress states and intrusion geometries during the formation of maar–diatreme complexes. Explosive excavation and infilling of diatremes affects local stress states which inhibits magma ascent and drives lateral diversion at various depths, which are expected to promote intra-diatreme explosions, host rock mixing, and vent migration. Our models demonstrate novel mechanisms explaining the generation of saucer-shaped sills, linked with magma diversion and enhanced intra-diatreme explosive fragmentation during maar-diatreme volcanism. Similar mechanisms will occur at other volcanic vents producing crater-forming eruptions.

Load Stress Controls on Directional Lava Dome Growth at Volcán de Colima, Mexico

“…These results are in agreement with previous studies investigating the ascent of magma in response to changing surface loads, which were found to occur due to a shift in principal stresses on a local (Le Corvec et al, 2018) and crustal scale (Maccaferri et al, 2017).…”

“…The stress-field pattern of a volcano is known to influence or even control the path of ascending magmas (Nakamura, 1977;Rivalta et al, 2015;Sulpizio and Massaro, 2017). In addition, recent studies show that loading or unloading of a volcanic edifice (Maccaferri et al, 2017) or a crater excavation and filling (Le Corvec et al, 2018) can reorient magma propagation. Here we investigate the response of edifice-stresses to load-changes associated with the addition and removal of the summit dome.…”

“…Another limitation of the model is the use of a 2D axisymmetric half-space to create a 3D model from a profile. This is a common simplification used in several similar studies (Chadwick et al, 1988;Corbi et al, 2016;Le Corvec et al, 2018) and is due to the difficult implementation of the large datasets and computing power that are required to use a full 3D surface model. While we manage to capture and include all important features including the conduit and vent positions, it is important to note that our model is derived from a change in topography of a 2D environment and is thus not a complete representation of the real morphology (e.g., variable crater depth or dome heights cannot be included).…”

Transition zone between the upper diatreme and lower diatreme: origin and significance at Round Butte, Hopi Buttes volcanic field, Navajo Nation, Arizona

“…The recent literature mentions dikes, sills, sheets and plugs as possible feeders of maardiatreme volcanoes (e.g. Re et al 2015Re et al , 2016Le Corvec et al 2018). In our model, for simplicity, we consider a dike, likely less than 1 m thick, as the feeder of the Round Butte diatreme.…”

“…Due to exposure constraints, most maar-diatreme studies focus on a specific part of the volcano, such as the ejecta ring and crater (e.g., Kienle et al 1980;White 1991;Vazquez and Ort 2006;Ort and Carrasco-Núñez 2009;Austin-Erickson et al 2011;Valentine et al 2015;Graettinger 2018), the upper diatreme (e.g., White 1991;White and Ross 2011;Delpit et al 2014), the lower diatreme (e.g., White 1991;Lefebvre et al 2013Lefebvre et al , 2016Bélanger and Ross 2018), or rarely, the root zone (Clement 1982;Lorenz and Kurszlaukis 2007) or the intrusive plumbing system (Re et al 2015(Re et al , 2016Muirhead et al 2016;Le Corvec et al 2018). The origin of the lower diatreme is still strongly debated in the literature (see discussion in Bélanger and Ross 2018).…”