The prophetic powers of Pythia, the woman of the ancient Delphic Oracle, at the Temple of Apollo in Greece, are said to have been induced by hydrocarbon vapors, specifically ethylene, rising from rock and producing neurotoxic effects, including trance and delirium. This study by Etiope et al. completes a trilogy of papers on the link between geology and archeology in Delphi. Gas occurrence, though not ethylene, was confirmed on the basis of detailed surveys of gas flux from soil, gas in groundwater, and isotopic analyses of spring scales. Etiope et al. provide evidence that little methane, ethane, and carbon dioxide are released from a thermogenic (catagenetic) hydrocarbon-prone environment. However, the possibility of significant ethylene emissions is not obvious. In neither the present nor the past could the deep carbonatic rocks of Delphi produce sufficient amounts of ethylene (hundreds of ppmv) to produce smelling vapors or generate neurotoxic effects on humans. The Temple of Apollo may have been the site of increased degassing of methane in the past. If gas-linked neurotoxic effects upon Pythia need to be invoked, they should be sought in the possibility of oxygen depletion due to CO2-CH4 exhalation in the indoor temple. Alternatively, a possible geological explanation behind the natural presence of sweet scents at the temple could be aromatic hydrocarbons, such as benzene, dissolved in the groundwater spring, the production of which in the Delphi rocks is theoretically possible, but remains to be experimentally proved.
The events that led up to the historically important eruption of Vesuvius volcano in A.D. 79 have been investigated and may assist in understanding the volcano in its current dormant state. By analyzing chemical variations within crystals found in A.D. 79 pumice, Morgan et al. have discovered that fresh hot magma rose into the Vesuvius system in at least four pulses before the eruption. These happened about 80 years, 40 years, and then twice around 20 years before the eruption. Morgan et al.'s method is likely to be applicable at other volcanoes and has the potential to reveal the timing of events that can potentially trigger volcanic eruptions.