The western edge of the first Jura plateau above Baume-les-Messieurs has the particularity of being deeply notched by narrow valleys called 'reculées' (blind valleys) which end in a cul de sac and are bordered by very steep slopes and rocky escarpments. They were shaped by a gradual retreat of the head of the valley inside the plateau following landslides of karst conduits amplified by the action of freezing and thawing. At the start of each 'reculée', there is always a cave or an underground network from which an exurgence gives rise to a stream which then flows through the bottom of the valley.