Effusion Rate Evolution During Small‐Volume Basaltic Eruptions: Insights From Numerical Modeling

Abstract

The temporal evolution of effusion rate is the main controlling factor of lava spreading and emplacement conditions. Therefore, it represents the most relevant parameter for characterizing the dynamics of effusive eruptions and thus for assessing the volcanic hazard associated with this type of volcanism. Since the effusion rate curves can provide important insights into the properties of the magma feeding system, several efforts have been performed for their classification and interpretation. Here, a recently published numerical model is employed for studying the effects of magma source and feeding dike properties on the main characteristics (e.g., duration, erupted mass, and effusion rate trend) of small-volume effusive eruptions, in the absence of syn-eruptive magma injection from deeper storages. We show that the total erupted mass is mainly controlled by magma reservoir conditions (i.e., dimensions and overpressure) prior to the eruption, whereas conduit processes along with reservoir properties can significantly affect mean effusion rate, and thus, they dramatically influence eruption duration. Simulations reproduce a wide variety of effusion rate trends, whose occurrence is controlled by the complex competition between conduit enlargement and overpressure decrease due to magma withdrawal. These effusion rate curves were classified in four groups, which were associated with the different types described in the literature. Results agree with the traditional explanation of effusion rate curves and provide new insights for interpreting them, highlighting the importance of magma reservoir size, initial overpressure, and initial width of the feeding dike in controlling the nature of the resulting effusion rate curve.

Thematic vent opening probability maps and hazard assessment of small-scale pyroclastic density currents in the San Salvador volcanic complex (El Salvador) and Nejapa-Chiltepe volcanic complex (Nicaragua)

“…Then, we considered the major fault structures present in the studied volcanic areas (Fig. 1a and b), which likely had a significant influence in the vent position of past events because of their effect in magma ascent dynamics (Gaffney and Damjanac, 2006;Valentine and Krogh, 2006;Ferrés et al, 2011;Avellán et al, 2012;Le Corvec et al, 2013).…”

“…A first hazard assessment exercise for BV was done by Ferrés et al (2013), considering ash fall, ballistic projectiles, and pyroclastic density currents issued from the central vent. However, since a recur- (Pardo et al, 2008;Freundt et al, 2010;Avellán et al, 2012 rence period of 85±50 years was proposed by Sofield (1998Sofield ( , 2004 for flank eruptions during Stage III, the most probable future event is associated with monogenetic volcanism, and thus the analysis of the hazard associated with flank eruptions is of paramount importance in the SSVC in order to complement the recent literature.…”

“…It includes at least 31 volcanic vents mainly emplaced following the Nejapa-Miraflores lineament (NML in Fig. 1b; Espinoza, 2007;Avellán et al, 2012). At its northern limit, the NCVC includes the polygenetic Apoyeque stratovolcano and several monogenetic volcanoes including maars, tuff rings, tuff cones, and scoria cones (Table 2, Avellán et al, 2012).…”

“…1b; Espinoza, 2007;Avellán et al, 2012). At its northern limit, the NCVC includes the polygenetic Apoyeque stratovolcano and several monogenetic volcanoes including maars, tuff rings, tuff cones, and scoria cones (Table 2, Avellán et al, 2012). One of these vents, named Tiscapa maar (vent 26 in the nomenclature presented in Fig.…”

Thematic vent opening probability maps and hazard assessment of small-scale pyroclastic density currents in the San Salvador Volcanic Complex (El Salvador) and Nejapa-Chiltepe Volcanic Complex (Nicaragua)

“…In other words, vent position is not only important for volcanic risk assessment because it controls the final dispersal of volcanic products, but also because it can be correlated with eruption style and intensity. A number of different volcanic processes may produce this correlation, such as the involvement of different portions of the plumbing system, the presence of groundwater or surface water in specific zones of the volcanic field, or variations in the mechanical characteristics of the country rocks (e.g., Andronico et al, 2005;Coppola et al, 2009;Aravena et al, 2020b). This is evident for example in partially submerged calderas, in which the style of activity of vents in the submerged zones is clearly influenced by their position.…”