From myth to whiff: how hot gases exiting Earth's crust were the source of fortune tellers' predictions...
Most people are acquainted with the myths of ancient Greece. We've heard of Hercules and Zeus, Aphrodite and Era, Achilles and possibly Ulysses. But what about the oracle of Delphi? This was a mystic place where the gods, who knew everything and saw everything, communicated with the wretched humans and revealed to them the path to glory.
Unlike the mythical heroes, however, this place really existed, and now new scientific research has demonstrated how the legend began - and it's all thanks to the peculiar geological setting of the area – a combination of active faults, seismic activity and a layer of coal! Indeed it seems that two thousands years of wars and battles may have have been won or lost thanks to the advice of women whose senses were dulled by methane blowing from a crack in the ground!
The oracle spoke through a local woman, the Pythia, who was chosen from among the peasants of the area. Documents provided by the Greek historian Plutarch (AD 46-120) describe the Pythia inhaling vapours from a fissure called Adyton. Shortly after she would go into a trance, which enabled her to contact Apollo, the god to whom the oracle was dedicated. Occasionally these trances deepened into delirium and even death, but more normally the woman would utter extremely cryptic and freely-interpretable rhymed answers, which were sometimes conflicting.
According to local legend, these powerful vapours were the breath of Piton, the sacred guardian of the temple. Apollo defeated her and closed her dragon-body in a deep cave under the surface, and the vapours inhaled by the Pythia corresponded to the beast’s breath.
From Myth to Whiff (of methane)...
Instead the local geology holds the key, as a more recent investigation by a Connecticut-based team of scientists has shown. The intellectual leap was made by Jelle Zeiling De Boer, a geologist from Wesleyan University. He connected the legendary vapours with ancient earthquakes triggered by two fault lines that intersect deep beneath the oracle.
The site of the Delphi Oracle sits on the northern flank of the Korint rift zone, which is the result of crustal thinning, fracturing and subsidence. The geological process began in the early Pliocene period (over four million years ago) when a huge submarine limestone plateau was broken up into long crustal slivers, which sank to form the Korinth rift zone.
Previously, Luigi Piccardi from the University of Florence in Italy studied this complex structure: the Delphi fault is the most prominent of the active structures of the Gulf of Corinth Rift. It is an east-west–trending normal fault, dipping to the south, with a minor right-lateral movement component. Seismic studies indicate that the fault is active, and Delphi sits right on top of it. But by exploring the underlying structure of the region he also provided the key to solving the mystery: because trapped deep undergound beneath a band of limestone is a thick layer of bituminous (coal-like) organic sediments.
De Boer realised that the vapours inhaled by the Pythia were likely to correspond to volatile hydrocarbons escaping from gas pockets in the bituminous sediments, and the release of the gases was provoked by fault movements.
Indeed De Boer found that the Delphi faults are NNW-SSE trending fractures which cross beneath the oracle site. Where faults join like this they can provide pathways through which ground water and gases can rise to the surface, especially in a tectonically active zone like the Corinth zone (the most important earthquake for this zone was the Corinth earthquake of 373 BC, which probably influenced the reactivation of the fault, as during each seismic event new pathways were created and additional volumes of gas may have been squeezed from the underlying formations).
The gases themselves are likely to include methane, carbon dioxide and hydrogen sulphide, which can bring about euphoric effects when inhaled. De Boer has also found evidence of small amounts of ethylene, which is known to provoke sensations of euphoria and buoyancy (just like for Mr. Burns in a famous Simpsons episode). However, two other geologists, Papatheodorou and Etiope argue that the percentage of limestone under the temple is not adequate to generate sufficient quantities of ethylene to provoke near-anaesthesia! Instead they suggest that the visions were induced by large doses of methane and carbon dioxide.
Nevertheless, both studies agree that the Pythia’s ecstatic trance was not induced by the presence of the god of the sun. Instead what made the Delphi oracle notorious (despite its architectural similarity to hundreds of oracle temples spread out along the Peloponnesus peninsula), was the unique geological setting, which gave the place an occult aura. So in some respects oracles are just like houses - it's all down to location, location, location!