Asphalt volcanoes and lava-like flows of solidified asphalt on the seafloor (Figure 1) were first discovered and described by MacDonald et al. . The flows covered more than one square kilometer of a dissected salt dome at abyssal depths (∼3000 m) in the southern Gulf of Mexico. “Chapopote” (93°26′W, 21°54′N) was one of two asphalt volcanoes they discovered. MacDonald et al. determined that the apparently fresh asphalt must initially have flowed in a hot state, and subsequently chilled, contracted, and solidified, much in the same way as normal lava does on the surface of the Earth.
The two asphalt-volcanoes discovered occur at the apex of salt domes that pierce through the seafloor. These “piercement salt domes,” known as the Campeche Knolls, are pertinent features of the deep Campeche Sedimentary Basin, which has a sediment thickness of about 10 km. According to conventional theory [Vendeville and Jackson, 1992], piercement salt domes represent “salt diapirs” that have risen up, due partly to density contrasts between salt and clay/sand from the “mother salt” located between 7 and 10 km below seafloor. A salt diapir is a vertical body of sub-surface salt, which is most often circular in cross section, is one to several kilometers in diameter, and can be 8–10 km high.