Eruptive activity of the Santorini Volcano controlled by sea-level rise and fall

Abstract

Sea-level change is thought to influence the frequencies of volcanic eruptions on glacial to interglacial timescales. However, the underlying physical processes and their importance relative to other influences (e.g. magma recharge rates), remain poorly understood. Here we compare a ~360 kyr long record of effusive and explosive eruptions from the flooded caldera volcano at Santorini (Greece) with a high resolution sea-level record spanning the last four glacial-interglacial cycles. Numerical modelling shows that when the sea level falls by 40 m below the present-day level, the induced tensile stresses in the roof of the magma chamber of Santorini trigger dyke injections. As the sea-level continues to fall to -70 or -80 m, the induced tensile stress spreads throughout the roof so that some dykes reach the surface to feed eruptions. Similarly, the volcanic activity gradually disappears after the sea-level rises above -40 m. Synchronising Santorini's stratigraphy with the sealevel record by using tephra layers in marine sediment cores shows that 208 out of 211 eruptions (both effusive and explosive) occurred during periods constrained by sea level falls (below -40m) and subsequent rises, suggesting a strong absolute sea-level control on the timing of eruptions on Santorini -a result that probably applies to many other volcanic islands around the world. Climate as a Driver of VolcanismThe climate system's influence on solid-earth processes, including volcanic and tectonic activity 1-4 is receiving increasing attention from researchers. Changes in surface loading by growth and retreat of ice-sheets have been linked to changes in volcanic activity in formerly glaciated areas on timescales from 10 3 -10 6 years [5][6][7][8][9][10][11] . Removal of an ice-sheet reduces the overburden pressure and results in additional decompression melting in the mantle. The associated stress changes in the crust facilitate dyke propagation to the surface, thereby increasing volcanic activity 10 . The effects of concomitant sealevel changes on volcanic activity, however, have not yet been firmly established. Because sea-level

Impact of climate change on volcanic processes: current understanding and future challenges

“…More generally, eruptive records show periodicities consistent with orbital scale climatic cycles (Schindlbeck et al, 2018), supporting relationships between hydrospheric mass distribution and magmatism. On the scale of individual edifices, ice retreat and sea-level change may influence flank stability (Quidelleur et al, 2008;Coussens et al, 2016) [hypothesised], magma migration (Hooper et al, 2011;Michaut et al 2020) [hypothesised] and the eruptibility of magma (Satow et al, 2021) by changing ocean bottom pressure and crustal stress conditions [hypothesised]. More generally, surface load distributions influence the balance between crustal magma storage and ascent, but the direction of these changes is highly dependent on the storage zone size, depth and shape as well as on the magma compressibility and lithospheric rheology (Albino et al, 2010;Sigmundsson et al, 2013) [uncertain].…”

Cryospheric Impacts on Volcano-Magmatic Systems

“…These "ablation rates" are significantly higher than those typically assigned to rates of erosion for most terrestrial environments (e.g., 0.0004 m/yr; Ferrier et al, 2007), or for rates of sea level rise during deglaciations (e.g., 0.01-0.04 m per year after the Last Glacial Maximum; Lambeck et al, 2006). After some lag time following rapid interglacial sea level rise, high strain rates combine with increased lithospheric loads to induce crustal stress regimes that suppress dike initiation and cause eruptions to cease in marinedominated environments (Satow et al, 2021). Thus, the characteristic slow loading rate and more rapid unloading rate of ice sheets can also be expected to impact magma source regions in glacial environments by altering the lithospheric stress conditions, influencing the depths and extents of melting, magma transport and storage processes, and pressure and temperature conditions of magma evolution (e.g., crystallization, devolatilization).…”

Impact of climate change on volcanic processes: current understanding and future challenges

“…More generally, eruptive records show periodicities consistent with orbital scale climatic cycles (Schindlbeck et al, 2018), supporting relationships between hydrospheric mass distribution and magmatism. On the scale of individual edifices, ice retreat and sea-level change may influence flank stability (Quidelleur et al, 2008;Coussens et al, 2016) [hypothesised], plumbing system development (Hooper et al, 2011;Michaut et al 2020) [hypothesised] and the eruptibility of magma (Satow et al, 2021) by changing ocean bottom pressure and crustal stress conditions [hypothesised]. More generally, surface load distributions influence the balance between crustal magma storage and ascent, but the direction of these changes is highly dependent on the storage zone size, depth and shape as well as on the magma compressibility and lithospheric rheology (Albino et al, 2010;Sigmundsson et al, 2013) [uncertain].…”