Climatic control on the location of continental volcanic arcs

Abstract

Orogens and volcanic arcs at continental plate margins are primary surface expressions of convergent plate tectonics. Although it is established that climate affects the shape, size, and architecture of orogens via orographic erosion gradients, the crustal upwelling of magmas and location of volcanic arcs have been considered insensitive to erosion. However, available data reveal westward migration of late-Cenozoic volcanic activity in the Southern Andes and Cascade Range where orography drives an eastward migration of the topographic water divide by increased precipitation and erosion along west-facing slopes. Here we use thermomechanical numerical modeling to show that orographic erosion and leeward topographic shift may entail asymmetric crustal structures, driving magma upwelling toward the region of enhanced erosion. Considering the different tectonic histories between the Southern Andes and the Cascade Range, the orographic erosion gradient is a plausible shared causal mechanism behind the late-Cenozoic westward migration of the regional volcanic arcs.

The arc-scale spatial distribution of volcano erosion implies coupled magmatism and regional climate in the Cascades arc, United States

“…The second phase (Figure 8B) shows how across-arc gradients in precipitation further drive divide migration. As has been demonstrated by previous studies, the divide migrates away from the wetter portion of the landscape (Bonnet, 2009;Goren et al, 2014;Muller et al, 2022). As localized magmatic uplift is still active in this phase, our model demonstrates that precipitation gradient effects can migrate the divide further eastward than the main locus of volcanic construction.…”

“…This kinematic model demonstrates that climate-driven arc migration over 10s of km can occur on 10s of Myr timescale, similar to rates observed globally under other subduction conditions (Karlstrom et al, 2014). This mechanism may occur over even shorter timescales as well (Muller et al, 2022), likely depending on the relative magnitudes (and spatial distribution) of magmatic uplift and asymmetric orographic erosion.…”

“…Second, this across-arc precipitation gradient creates spatial asymmetry in surface erosion between the windward and leeward sides of the arc. Both of these relationships have been well-documented in other environments, including arcs (England and Molnar, 1990a;Ferrier et al, 2013;Muller et al, 2022), and can feed back mechanically on the shallow magma plumbing system, coupling climate and magmatism on long timescales.…”

“…From the spatial distributions of both volcanic edifices and eroded edifice volumes, we hypothesize that long-term climate-volcanism coupling may influence patterns of magmatism. We focus on arc front migration as one possible outcome of this coupling (Karlstrom et al, 2014;Muller et al, 2022).…”

“…Orographic precipitation driven by arc mountain building focuses erosion on the windward side of the arc front, and provides a means for such long-term modulation of surface loads. Models of landscape evolution in response to regional climate gradients suggest that non-uniform precipitation causes regional-scale divide migration towards drier regions (e.g., Roe et al, 2003;Goren et al, 2014;Muller et al, 2022) in orogenic settings. Similarly, topographic loading has been shown to influence underlying shallow crustal stresses and modify dike trajectories that guide volcanic vent locations and their migration towards the load through time (e.g., Kervyn et al, 2009;Rivalta et al, 2019).…”