Hydrothermal eruptions at unstable crater lakes: Insights from the Boiling Lake, Dominica, Lesser Antilles

Rott, Stefanie; Scheu, Bettina; Montanaro, Cristian; Mayer, Klaus; Joseph, Erouscilla P. und Dingwell, Donald B. (2019): Hydrothermal eruptions at unstable crater lakes: Insights from the Boiling Lake, Dominica, Lesser Antilles. In: Journal of Volcanology and Geothermal Research, Bd. 381: S. 101-118

Abstract

The Boiling Lake-a major touristic attraction in the Morne Trois Pitons National Park, Dominica's (West Indies) World Heritage site-is located in an area of high hydrothermal activity in the southern part of the island. This spectacular lake is characterized by unstable behavior which has been interpreted to result from the presence of a water body above a fluctuating gas-filled, or multi-phase vent system. The system produces a near-boiling lake that occasionally drains and refills with water, without any simple periodicity. Despite the fact that such unstable draining lakes are thought to be non-eruptive, the Boiling Lake is known to have sourced occasional small hydrothermal eruptions as well as toxic gas emissions which accompany the refilling phase of these drainage events. Similar explosive events seem also to be likely after landslide slumped rocks from steep altered crater walls cover the vent area in the lake leading to overpressurized conditions. In both cases, rock expulsion and gas release continue to pose serious threats for tourists and tour guides. While conceptual models exist describing possible mechanisms of the Boiling lake drainage itself, little information exists to date regarding the trigger mechanisms related to the explosive events. Further, no estimation of the eruption processes and dynamics of these events has previously been attempted. To address this knowledge gap, we employ here a combined field-and laboratory-based approach in order to i) characterize the properties of the dominant lithologies from the crater walls at Boiling Lake, ii) determine how the ongoing alteration may affect their petrophysical properties (e.g., porosity and permeability), and iii) evaluate how water-saturated, unconsolidated wall rock materials behave when rapidly decompressed from a slightly elevated pressure and temperature conditions. Here, we propose that it is the petrophysical state of the materials involved (e.g. porosity, permeability and alteration-related strength) which controls the style and energy of these eruptions, as well as the potential for landslides from the crater walls. The experimentally simulated scenarios included in this study are: i) decompression from only slightly elevated pressure conditions inferred for small hydrothermal eruptions occurring after lake drainage events, and ii) decompression from rapidly enhanced pressure conditions produced by the capping and overpressurization of the vent area following landslide episodes. Ejection velocities obtained from rapid decompression experiments were used as input parameters for ballistic trajectory calculations, allowing for estimation of the potential area impacted by ejected debris. We anticipate that this study will serve as a contribution to the understanding of the hazard potential of future hydrothermal eruptions at unstable crater lakes in general, as well as providing direct insights into the ongoing hydrothermal activity at the Boiling lake. (C) 2019 The Authors. Published by Elsevier B.V.

• Dokumententyp: Zeitschriftenartikel
• Fakultät: Geowissenschaften > Department für Geo- und Umweltwissenschaften
• Themengebiete: 500 Naturwissenschaften und Mathematik > 550 Geowissenschaften, Geologie
• ISSN: 0377-0273
• Sprache: Englisch