Pyroclastic density currents are among the most catastrophic events of explosive eruptions in terms of loss of lives and damage to infrastructure. Since the late nineteenth century, the victims of explosive events have been estimated as high as 50.000, and the hazard is continuously increasing due to the progressive urbanization, which in many regions of the planet involves areas very close to active volcanoes. This session invites contributions targeted at investigating the interaction between pyroclastic density currents and topography (or any other artificial barrier) through numerical modeling and experiments, as well as field and geophysical studies of the currents’ deposits. Combined approaches, one integrating and constraining the other, are particularly welcome to focus on the complex nature of the interaction. The fundamental problem to be addressed is how much the sedimentary structures of the deposits depend on the topography, or may be a relict of what happens at the volcano crater. The numerical modeling of explosive eruptions, which is more and more often used to evaluate the volcanic hazard, would benefit from this state of the art on pyroclastic flow-topography interaction.