Abstract

Ancient authors from Plato to Pausanias have left descriptions of Delphi’s oracle and its mantic sessions. The latter were interpreted as events in which the Pythia (priestess) placed herself on a tripod over a cleft (fissure) in the ground below the Apollo temple. Here she inhaled a vapour rising from the cleft, and became inspired with the power of prophecy. French archaeologists who excavated the oracle site at the turn of the century reported no evidence of either fissures or gaseous emissions and concluded that the ancient accounts were myths. As a result, modern classical scholars and many archaeologists reject the ancient testimonies concerning the mantic sessions and their geological origin. However, the geological conditions at the oracle site do not a priori exclude the early accounts. A major WNW-ESE fault zone and a minor swarm of NNW-SSE fractures intersect below the site. These intersection(s) provided pathways for rising ground water, including a spring below the Apollo temple. The faults broke through a bituminous limestone formation at relatively shallow depth. Hydrocarbon gases that originated in this formation may have escaped during and after seismo-tectonic events. Such gases can induce mild narcotic effects. It is highly probable therefore that the Pythia’s inspiration resulted from the inhalation of light hydrocarbon gases, which rose along a fissure (fracture) in the adyton below the Apollo temple.