Hydraulic fracturing (‘fracking') has enabled the recovery of previously inaccessible resources and rendered new areas of the underground ‘productive’. While a number of studies in the US and UK have examined public attitudes toward fracking and its various impacts, how people conceptualise the deep underground itself has received less attention. We argue that views on resources, risk and the deep underground raise important questions about how people perceive the desirability and viability of subterranean interventions. We conducted day-long deliberation workshops (two (...) in each country), facilitating discussions among diverse groups of people on prospective shale extraction in the US and UK. Themes that emerged in these conversations include seeing the Earth as a foundation; natural limits (a greater burden than the subsurface can withstand versus simply overuse of natural resources); and ideas about the fragility, instability and opacity of the deep underground. We find that concerns in both countries were not limited to specific, localised impacts but also addressed ecosystem links between surface and subsurface environments and broader questions about the use, identification and value of natural resources. (shrink)