**Allen F. Glazner**

Department of Geological Sciences, University of North Carolina, Chapel Hill, NC 27599-3315, USA; afg@unc.edu

Received: 2 February 2020; Accepted: 26 February 2020; Published: 1 March 2020

**Abstract:** Whether magma accumulating in the crust develops into a persistent, eruptible magma body or an incrementally emplaced pluton depends on the energy balance between heat delivered to the bottom in the form of magma and heat lost out the top. The rate of heat loss to the surface depends critically on whether heat transfer is by conduction or convection. Convection is far more e fficient at carrying heat than conduction, but requires both abundant water and su fficient permeability. Thus, all else being equal, both long-term aridity and self-sealing of fractures should promote development of persistent magma bodies and explosive silicic volcanism. This physical link between climate and magmatism may explain why many of the world's grea<sup>t</sup> silicic ignimbrite provinces developed in arid environments, and why extension seems to suppress silicic caldera systems.

**Keywords:** igneous petrology; tectonics; heat flow; glaciation; climate
