Chapter 20 - Glaciovolcanism

Abstract

Glaciovolcanism (a.k.a., subglacial volcanism, volcano–ice interaction) involves all interactions between magmatic-volcanic systems and ice in any form, including meltwater derived directly from ice melting. The earliest studies to recognize connections between characteristic volcanic deposits and an ice-rich environment were conducted in Iceland (1920s) and British Columbia, Canada (1940s). Almost a century later, glaciovolcanic deposits have been identified on all terrestrial continents, except Australia, and on Mars. The “classic” tuya model provides a generalized account of the dominant processes extant during a volcanic eruption beneath ice, including (1) transitions in eruptive style from effusive to explosive (or vice versa), (2) growth and emergence of volcanoes from subaqueous to subaerial environments (i.e., passage zones), and (3) waning of the eruption commonly expressed by effusion of lavas to cap the tuya. While the model has general application to the entire magmatic compositional spectrum, intermediate to felsic glaciovolcanic eruptions appear to preserve a less diagnostic record of interactions with ice owing to their higher viscosities and to their capacity to form glassy deposits even in subaerial environments. Recognition of glaciovolcanic origins for volcanic edifices and deposits is important well outside of classical volcanology. Glaciovolcanic deposits serve as valuable proxies for paleoclimate reconstructions by delineating the spatial and temporal limits of Quaternary ice sheets on Earth and also are used to map ice sheet distributions on Mars. Additionally, as demonstrated by recent eruptions at Gjálp (1996), Eyjafjallajökull (2010), and Redoubt (2009), volcano–ice interactions produce a unique set of local and regional hazards in both remote and urban areas that are critical to understand in order to protect strategic infrastructure and growing human populations.