Climate effects on volcanism: influence on magmatic systems of loading and unloading from ice mass variations, with examples from Iceland

Abstract

Pressure influences both magma production and the failure of magma chambers. Changes in pressure interact with the local tectonic settings and can affect magmatic activity. Present-day reduction in ice load on subglacial volcanoes due to global warming is modifying pressure conditions in magmatic systems. The large pulse in volcanic production at the end of the last glaciation in Iceland suggests a link between unloading and volcanism, and models of that process can help to evaluate future scenarios. A viscoelastic model of glacio-isostatic adjustment that considers melt generation demonstrates how surface unloading may lead to a pulse in magmatic activity. Iceland's ice caps have been thinning since 1890 and glacial rebound at rates exceeding 20 mm yr −1 is ongoing. Modelling predicts a significant amount of 'additional' magma generation under Iceland due to ice retreat. The unloading also influences stress conditions in shallow magma chambers, modifying their failure conditions in a manner that depends critically on ice retreat, the shape and depth of magma chambers as well as the compressibility of the magma. An annual cycle of land elevation in Iceland, due to seasonal variation of ice mass, indicates an annual modulation of failure conditions in subglacial magma chambers.

Glacial Isostatic Adjustment modelling: historical perspectives, recent advances, and future directions

“…Postglacial rebound acts to reduce the pressure in the mantle, and this has been implicated in promoting terrestrial volcanism (Sigmundsson et al, 2010;Praetorius et al, 2016). Huybers and Langmuir (2009) argue that the CO 2 release associated with increased volcanism during the last deglaciation may have been sufficient to promote further ice melt, raising the possibility that glacial rebound, CO 2 release, and ice dynamics are part of a positive feedback loop.…”

Inelastic compaction and permeability evolution in volcanic rock

“…Shimada et al, 1989;Heap et al, 2015a;Zhu et al, 2016), as well as being heavily reliant on its initial porosity (Heap et al, 2015a;Zhu et al, 2016) and other factors such as temperature (Violay et al, 2012(Violay et al, , 2015Heap et al, 2017) and alteration (Siratovich et al, 2016). In detail, high effective pressures and/or high initial porosity promote ductile behaviour, whereas dilatant brittle failure is favoured in low-porosity volcanic rock deformed under a range of effective pressures.…”

“…Magma is a constantly developing multi-phase medium, and as it migrates through the crust, vesiculating and crystallising along the way, it can impart significant mechanical stress on the surrounding edifice rock (e.g. Sparks, 1997;Voight et al, 1998;Denlinger and Hoblitt, 1999;Clarke et al, 2007;Heimisson et al, 2015). Deeper in the crust, magma chamber deformation can pressurise conduit and dyke systems above, in turn displacing the edifice (e.g.…”

“…Furthermore, the overlying stress may be influenced by loading and unloading of volcanoes by ice, for example, either seasonally or due to longer-scale climatic variations (e.g. Sigmundsson et al, 2010).…”

“…The expansion of exsolved gas species, which occurs as volatile-laden magma approaches the surface of the Earth, can generate overpressures in the magma: the kinetic engine that typically drives explosive fragmentation (e.g. Sparks, 1978). If the permeability of a volcanic system (including the edifice) is high, volatiles may escape from the magma and the propensity for explosive behaviour may be reduced; conversely, low system permeability could promote pressure build-up and violent eruptive activity, a concept underlying numerous studies in volcanology (for example Eichelberger et al, 1986;Woods and Koyaguchi, 1994;Rust et al, 2004;Edmonds and Herd, 2007;Mueller et al, 2008Mueller et al, , 2011Nguyen et al, 2014;Okumura and Sasaki, 2014;Gaunt et al, 2014).…”