Historic hydrovolcanism at Deception Island (Antarctica): implications for eruption hazards

Abstract

Deception Island (Antarctica) is the southernmost island of the South Shetland Archipelago in the South Atlantic. Volcanic activity since the eighteenth century, along with the latest volcanic unrest episodes in the twentieth and twenty first centuries, demonstrates that the volcanic system is still active and that future eruptions are likely. Despite its remote location, the South Shetland Islands are an important touristic destination during the austral summer. In addition, they host several research stations and three summer field camps. Deception Island is characterised by a Quaternary caldera system with a post caldera succession and is considered to be part of an active, dispersed (monogenetic), volcanic field. Historical post caldera volcanism on Deception Island involves monogenetic small volume (VEI 2-3) eruptions such forming cones and various types of hydrovolcanic edifices. The scientific stations on the island were destroyed, or severely damaged, during the eruptions in 1967, 1969, and 1970 mainly due to explosive activity triggered by the interaction of rising (or erupting) magma with surface water, shallow groundwater, and ice. We conducted a detailed revision (field petrology and geochemistry) of the historical hydrovolcanic post caldera eruptions of Deception Island with the aim to understand the dynamics of magma water interaction, as well as characterise the most likely eruptive scenarios from future eruptions. We specifically focused on the Crimson Hill (estimated age between 1825 and 1829), and Kroner Lake (estimated age between 1829 and 1912) eruptions and 1967, 1969, and 1970 events by describing the eruption mechanisms related to the island's hydrovolcanic activity. Data suggest that the main hazards posed by volcanism on the island are due to fallout, ballistic blocks and bombs, and subordinate, dilute PDCs. In addition, Deception Island can be divided into five areas of expected activity due to magma water interaction, providing additional data for correct hazard assessment on the island.

Deciphering the evolution of Deception Island’s magmatic system

“…Recent post-caldera volcanic activity on DI mostly consists of small volume eruptions (e.g., <0.1 km 3 ) 3,24,36 with variable degrees of explosivity depending on the water amount and source (i.e., aquifer, sea, ice melting, etc.) that interacted with the rising or erupting magma 3,15,51,52 .…”

“…The compositional variability of the 1967 and 1970 eruptive products, which depict approximately linear trends in binary diagrams, have been interpreted as related to mingling and mixing processes, as well as stratification of the magma reservoir 15 (named R4, Supplementary Materials 5 and 8). In contrast to the wide compositional range of the 1967 and 1970 eruptions feeding reservoir, some eruptive cones emitted compositionally very restricted magmas 3,52 , indicating that more homogeneous magma reservoirs are also present in the system (e.g., Kroner Lake eruption, reservoir R3)(Fig. 5).…”

δD and δ18O variations of the magmatic system beneath Deception Island volcano (Antarctica): Implications for magma ascent and eruption forecasting

“…Current degassing of Deception Island magmas in a closed-system scenario is also supported by the negligible contribution of primary magmatic component into the fumarolic gas and hot spring waters in the island (Kusakabe et al, 2009), despite the shallow depth of the most recently formed magma reservoirs (Geyer et al, 2019). Fast ascent and quenching of magmas during explosive phreatomagmatic eruptions in Deception Island is also supported by petrography of the pyroclastic samples (Pedrazzi et al, 2018;Geyer et al, 2019).…”

“…Shallow faults, among other key geological features, such as shallow soft-sediment cover, topography and proximity to seawater, can strongly influence eruption styles in monogenetic volcanoes (Kereszturi et al, 2017). At Deception Island, a similar set of factors may have influenced magma-water interactions, resulting in Surtseyan style and phreatomagmatic eruptions (Pedrazzi et al, 2018;Geyer et al, 2019). This geographical correlation is also observable in the pre-and syn-caldera deposits, i.e.…”

Introduction to volcanism in Antarctica: 200 million years of subduction, rifting and continental break-up

“…The presence of relict heat (Mount Berlin, Mount Melbourne and Mount Rittmann) and abundant englacial and marine tephras sourced in Mount Takahe, Mount Berlin, Mount Waesche, Mount Rittmann and, possibly, The Pleiades indicate that many others were active in recent geological time (<10 ka: Lee et al 2019;Dunbar et al 2021;Gambino et al 2021;Narcisi and Petit 2021;Di Roberto et al 2021). Three of the volcanoes are, or have been, monitored (Deception Island, Mount Erebus and Mount Melbourne) but only one has published hazard and risk assessments (Deception Island: Bartolini et al 2014;Pedrazzi et al 2018;Geyer et al 2021).…”