Abstract The reuse of traditional construction materials attests to their high value over the long term. In fact, the practice has always demonstrated the inherent value of traditional raw materials and their products in confronting the issues of sustainability, in the broader sense of preserving resources – material and immaterial – for future generations. Throughout the history of building, the symbolic value of spolia (i.e. the use of ancient architectural elements in new construction) has gone hand-in-hand with the practice of recycling, demonstrating, at various levels, an intrinsic awareness of reuse as a tool for minimizing waste of materials and energy. Today, sustainability is rarely considered from a long-term perspective, and when it is, the approach tends to be from a broad theoretical standpoint. In the past, however, it was a common and necessary aspect of construction management, when the waste of materials was a forbidden luxury. This paper presents a review of the reuse of geomaterials, mainly stone, throughout the Italian history of construction, indicating major examples selected for their value as memorable references, describing common practices from antiquity to modern times, and concluding with a description of the actual state of the art of the practice, based on very recent and outstanding cases.

Abstract Arrival of magma from depth into shallow reservoirs has been documented as one of the possible processes leading to eruption. Magma intruding and rising to the surface interacts with the already emplaced, degassed magmas residing at shallower depths, leaving chemical signatures in the erupted products. We performed two-dimensional numerical simulations of the arrival of gas-rich magmas into shallow reservoirs. We solve the fluid dynamics for the two interacting magmas, evaluating the space–time evolution of the physical properties of the mixture. Convection and mingling develop quickly into the chamber and feeding conduit/dyke, leading on longer timescales to a density stratification with the lighter, gas-richer magma, mixed with different proportions of the resident magma, rising to the top of the chamber due to buoyancy. Over timescales of hours, the magmas in the reservoir appear to have mingled throughout, and convective patterns become harder to identify. Our simulations have been performed changing the geometry of the shallow reservoir and the gas content of the initial end-member magmas. Horizontally elongated magma chambers, as well as higher density contrasts between the two magmas, cause faster ascent velocities and also increase the mixing efficiency. Supplementary material: Videos showing the evolution of magma composition with time in the shallow chamber for simulations 1–4 are available at www.geolsoc.org.uk/SUP18819