Failed magmatic eruptions: late-stage cessation of magma ascent

Abstract

When a volcano becomes restless, a primary question is whether the unrest will lead to an eruption. Here we recognize four possible outcomes of a magmatic intrusion: "deep intrusion", "shallow intrusion", "sluggish/viscous magmatic eruption", and "rapid, often explosive magmatic eruption". We define "failed eruptions" as instances in which magma reaches but does not pass the "shallow intrusion" stage, i.e., when magma gets close to, but does not reach, the surface. Competing factors act to promote or hinder the eventual eruption of a magma intrusion. Fresh intrusion from depth, high magma gas content, rapid ascent rates that leave little time for enroute degassing, opening of pathways, and sudden decompression near the surface all act to promote eruption, whereas decreased magma supply from depth, slow ascent, significant enroute degassing and associated increases in viscosity, and impingement on structural barriers all act to hinder eruption. All of these factors interact in complex ways with variable results, but often cause magma to stall at some depth before reaching the surface. Although certain precursory phenomena, such as rapidly escalating seismic swarms or rates of degassing or deformation, are good indicators that an eruption is likely, such phenomena have also been observed in association with intrusions that have ultimately failed to erupt. A perpetual difficulty with quantifying the probability of eruption is a lack of data, particularly on instances of failed eruptions. This difficulty is being addressed in part through the WOVOdat database. Papers in this volume will be an additional resource for scientists grappling with the issue of whether or not an episode of unrest will lead to a magmatic eruption.

Strengths and strain energies of volcanic edifices: implications for eruptions, collapse calderas, and landslides

“…Other recent papers on this and related topics include Canon-Tapia et al (2006), Menand et al (2010), Geshi et al (2010Geshi et al ( , 2012, Taisne et al (2011), and Maccaferri et al (2010, 2011. A detailed statistical summary of "failed eruptions" (mostly arrested dikes) is provided by Moran et al (2011).…”

Volcanic deformation of Atosanupuri volcanic complex in the Kussharo caldera, Japan, from 1993 to 2016 revealed by JERS-1, ALOS, and ALOS-2 radar interferometry

“…Thus, as the supply of new magma from deep below the surface continued, there was no other route for the stagnant magma, which was blocked from rising further, other than to migrate laterally. The answer to the second question might be that the initial rate of magma supply from depth decreased and that gradual degassing from the magma remaining in the sill after the ascent reduced its buoyancy, which resulted in the descent or drainback of magma to depths further below the surface (Moran et al 2011). …”

Santorini unrest 2011–2012: an immediate Bayesian belief network analysis of eruption scenario probabilities for urgent decision support under uncertainty

“…Failed intrusion/eruption episodes represent a major challenge for civil protection decision making. Moran et al (2011) present a valuable summary of the diverse spectrum of states of unrest that can accompany a failed eruption. However, they were unable to offer any quantitative hint of how often such stillborn eruptions are the outcome of significant episodes of unrest at volcanoes generally, and there is no basis at all for assessing the probability of this scenario for Santorini.…”