Host Rock Variability Powers the Diversity of Steam‐Driven Eruptions

Abstract

Steam-driven, phreatic and hydrothermal eruptions are a common explosive phenomenon in volcanic and geothermal systems (Browne & Lawless, 2001; Stix & Moor, 2018). In active volcanic terrains, phreatic eruptions may be triggered by the sudden arrival of extra fluid (gas, waters or brines) interacting with heat from intruding magma (Browne & Lawless, 2001; Stix & Moor, 2018). In geothermal settings, hydrothermal eruptions may be triggered by depressurization and steam-flashing of trapped hot pressurized fluids, released by earthquakes, landslides, or other localized natural hydrological disturbances (Browne & Lawless, 2001; Mastin, 1995; Thiéry & Mercury, 2009). Moreover, in both active volcanic and geothermal settings, hydrothermal alteration and mineral sealing can promote high local overpressures and thus more readily an explosive destabilization (Mayer et al, 2015, 2016; Scolamacchia & Cronin, 2016). Irrespective of the presence of shallow magma, flashed water contains enough energy to efficiently fragment rock and violently eject material upwards and laterally (Montanaro et al., 2016a; Morgan et al., 2009). Often impulsive and shortlived relative to magmatic eruptions, they are still deadly due to their sudden onsets, and the generation of violent blasts (

Magmatic and phreatomagmatic contributions on the ash-dominated basaltic eruptions: Insights from the April and November–December 2005 paroxysmal events at Karthala volcano, Comoros

“…The presence of large (up to meters) blocks of old and dense lavas within proximal fallout areas (Figs. 2e, S1c and S3c), suggests the occurrence of thermohydraulic explosions (Thiéry and Mercury, 2009;Montanaro et al, 2021) and associated shock waves (Büttner et al, 2005) able to fragment and project these ballistics (Fig. 12), originating from dense, crystallized and sometimes oxidized lava and micro-gabbro units that are visible on the crater walls (Fig.…”

The dynamic floor of Yellowstone Lake, Wyoming, USA: The last 14 k.y. of hydrothermal explosions, venting, doming, and faulting

“…Hydrothermal explosions involving liquid flashing to steam are top-down explosions with the near-surface material ejected first and the deepest part of the system ejected last in each explosion cycle or pulse (Fig. 15; Browne and Lawless, 2001;D'Elia et al, 2020;Gallagher et al, 2020;Mastin, 1991;McKibbin, 1990;McKibbin et al, 2009;Smith and McKibbin, 2000;Montanaro et al, 2020b;Morgan et al, 2009). Elliott's Crater is still active; in fact, large (30 to 80 cm diameter), subrounded rocks on the surficial sediments of the southeast crater rim (Fig.…”

“…Hydrothermal explosions, unrelated to magmatic eruptions, have emerged as one of the most important and least understood geologic hazards in Yellowstone National Park (YNP), Wyoming, USA, and similar volcanic and hydrothermal areas worldwide (Browne and Lawless, 2001;Christiansen et al, 2007;D'Elia et al, 2020;Lowenstern et al, 2005;Montanaro et al, 2016aMontanaro et al, , 2016bMontanaro et al, , 2020aMontanaro et al, , 2020b. The northern Yellowstone Lake area is characterized by a combination of high heat flow above a large magma reservoir in the collapsed 631 k.y.…”