The effect of deglaciation on mantle melting and crustal dike propagation: Iceland vs. Yellowstone

Abstract:

Deglaciation-enhanced magmatism has implications for natural hazards and may affect the Earth’s climate, either by releasing aerosols or volatiles into the atmosphere or by accelerating the flow of glaciers by heating their base. The link between the retreat of an ice cap and enhanced volcanism is most strongly established in Iceland, yet this link is less well-understood in magmatic intraplate settings such as Yellowstone. Deglaciation can affect volcanism by either 1) enhancing decompression melting in the mantle¹, 2) diverting dike pathways through the lithosphere or crust², or 3) triggering eruptions of pre-existing magma chambers³. All of these mechanisms have been modelled in Iceland, where increases in eruptive fluxes can be explained by some combination of a net increase in (mantle) melt generation and changes in (crustal) eruption timing. In contrast, the deglaciation of the Yellowstone ice cap did not observably enhance volcanism⁴. To explain these conflicting observations, we model the magmatic response to deglaciation of Iceland and Yellowstone, capturing both enhanced decompression melting in the asthenosphere and the effect of stress changes in the lithosphere and crust on dike initiation and propagation. For Iceland, we find the extensional stresses from plate spreading are key to enhancing the eruption of mantle melts. Applying the same model to Yellowstone, we find that while significant mantle melt volumes are produced due to decompression, dike paths are diverted where the lithosphere and crust are under compression, inhibiting eruption. Our model supports the hypothesis that lithospheric extension is paramount in enhancing eruptions due to deglaciation. We predict that while compressional intraplate systems may still produce large mantle melt volumes in response to deglaciation, much of this extra melt remains trapped in the lithosphere or crust, implying the delayed outgassing of volatiles.

1 Jull & McKenzie, 1996, J. Geohys. Res.

2 Hooper et al., 2011, Nat. Geo.

3 Jellinek et al., 2004, J. Geophys. Res.

4 Licciardi et al., 2018, Quat. Sci. Rev.