Abstract
In tectonic settings where decompression melting drives magmatism, there is compelling evidence that changes in ice loading or water loading across glacial-interglacial cycles modulate volcanic activity. In contrast, the response of subduction-related volcanoes remains unclear. A high-resolution postglacial eruption record from a large Chilean stratovolcano, Mocho-Choshuenco, provides new insight into the arc magmatic response to ice-load removal. Following deglaciation, we identify three distinct phases of activity characterized by different eruptive fluxes, sizes, and magma compositions. Phase 1 (13–8.2 ka) was dominated by large dacitic and rhyolitic explosive eruptions. During phase 2 (7.3–2.9 ka), eruptive fluxes were lower and dominated by moderate-scale basaltic andesite eruptions. Since 2.4 ka (phase 3), eruptive fluxes have been elevated and of more intermediate magmas. We suggest that this time-varying behavior reflects changes in magma storage time scales, modulated by the changing crustal stress field. During glaciation, magma stalls and differentiates to form large, evolved crustal reservoirs. Following glacial unloading, much of the stored magma erupts (phase 1). Subsequently, less-differentiated magma infiltrates the shallow crust (phase 2). As storage time scales increase, volcanism returns to more evolved compositions (phase 3). Data from other Chilean volcanoes show a similar tripartite pattern of evacuation, relaxation, and recovery, suggesting that this could be a general feature of previously glaciated arc volcanoes.
Highlights
Volcanism exerts a major influence on Earth’s atmosphere and surface environments (e.g., Schmidt et al, 2015)
We identify three phases of activity, with distinct time-averaged eruptive fluxes, eruption sizes, magma compositions, and temperature ranges (Fig. 1): phase 1 (13.0–8.2 ka), phase 2 (7.3–2.9 ka), and phase 3 (2.4 ka to present; age range given by mean eruption ages bounding the phase)
Given the relatively short time scales (~10 k.y.) considered here, we assume that magma fluxes into the crust are quasi-steady, and consider how the storage time scales within the crust might change
Summary
Volcanism exerts a major influence on Earth’s atmosphere and surface environments (e.g., Schmidt et al, 2015). Understanding feedbacks between climate and long-term changes in rates or styles of volcanism is important, but unresolved. In regions dominated by decompression melting (e.g., oceanic ridges and some continental volcanic fields) there is mounting evidence that unloading by ice removal or changing sea level influences the amount of mantle melting and magmatic fluxes into the crust (e.g., Jull and McKenzie, 1996; Nowell et al, 2006; Crowley et al, 2015). Empirical data on arc eruption rates through time remain ambiguous, and attempts to identify whether, or how, subduction-related volcanoes respond to ice-unloading remain inconclusive (e.g., McGuire et al, 1997; Singer et al, 2008; Watt et al, 2013)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
