Mechanisms of Crater Lake Breaching Eruptions

Abstract

In this chapter we review physical models on phreatomagmatic, phreatic, hydrothermal, and geyser-like eruptions and, for the first time, place them in a crater lake context. Examples of known crater lake systems for the different eruption types are provided. Besides the direct injection of a fresh magma into a crater lake, leading to phreatomagmatic activity, a crater lake is a strong condensing medium, sensitive to sudden pressure changes when injected by gas-vapor batches, which can lead to non-magmatic, though violent eruptions. The implosive nature, the role of the heat pipe and molten sulfur pool at the lake bottom are central in the phreatic eruption model. Contrary to phreatic eruptions, hydrothermal eruptions are instigated by a sudden pressure drop, causing boiling and vapor release, rather than by the input of a gas-vapor phase of magmatic origin. Geyser-like activity beneath or near crater lakes is analog to classic geysering, and becomes more obvious when lake water level is low. Although not explosive, the peculiar lake drainage and refill cycles of two lakes are discussed. The first outcomes of numerical simulation approaches help to better quantify injection pressure and vapor/liquid proportions of the input fluid. We stress that the various manifestations of eruptive activity at crater lakes is not necessarily linked to changes in magmatic activity, which could lead to misleading interpretations regarding volcano monitoring.