About every 100 years a major earthquake rattles the faults. The faults are heated by adjacent rocks and the hydrocarbon deposits stored in them are vaporized. These gases mix with ground water and emerge around springs.
De Boer conducted an analysis of these hydrocarbon gases in spring water near the site of the Delphi temple. He found that one is ethylene, which has a sweet smell and produces a narcotic effect described as a floating or disembodied euphoria.
"Ethylene inhalation is a serious contender for explaining the trance and behavior of the Pythia," said Diane Harris-Cline, a classics professor at The George Washington University in Washington, D.C.
"Combined with social expectations, a woman in a confined space could be induced to spout off oracles," she said.
According to traditional explanations, the Pythia derived her prophecies in a small, enclosed chamber in the basement of the temple. De Boer said that if the Pythia went to the chamber once a month, as tradition says, she could have been exposed to concentrations of the narcotic gas that were strong enough to induce a trance-like state.
The power of the Delphic oracle fluctuated and eventually lost favor as Christianity became the dominant religion of the land, said De Boer. Moreover, ancient legend suggests that the concentration of the vapors became weakerpossibly because the absence of a major earthquake failed to keep Earth's narcotic juices flowing.
Today, the water that helped transport the gases to the Delphic temple is tapped and siphoned above the temple to supply the modern town of Delphi.
The work by De Boer and his colleagues is an example of modern science helping archaeologists understand how ancient peoples lived. Another example among the ancient Greeks is the belief in Poseidon as the god of the sea and earthquakes. According to Harris-Cline, modern science associates the two with tectonic movement deep under the sea.
"Our scientific techniques are just beginning to detect the natural phenomena which the Greeks celebrated and appreciated 2,500 years ago with ritual activities at these special places," she said.
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