Management and development policies for natural heritage sites are experiencing a growing demand for monitoring and evaluation. This concerns in particular the tourist and leisure activities which raise fears related to the risks of degradation of the environment and expectations related to the potential effects on the economic development of the territories. The paper proposes an analytic framework of the economic effects of this frequentation that we apply to the Chaîne des Puys - Limagne fault tectonic arena site, that was included in the UNESCO World Heritage list in 2018. We carried out a tourist frequentation modeling of the site based on diverse partial and heterogenous data and a face to face survey of the visitors. The data processing reveal theoretical and methodological issues quantifying and qualifying the global frequentation (open and extended site, visitors' motivations and practices )), the monetary contribution constituted by the visitors' expenses (localization adjustments) and the local economic effects (visitors and expenses qualification, visitor conversion of expenses into direct and induced employment). Moreover, the analytic framework presented allows to shed additional light on the extensive system of tourism and leisure activities linked to the site and on any specific thematic issues, such as the comparison between the contributions of tourists and excursionists. In our case study, tourist spending on accommodation is largely dominant, and tourist spending far exceeds that of excursionists. Nevertheless, spending by excursionists represents a significant resource (accounting for 26% of spending on paid activities), and one that is better distributed throughout the year.