Nevado del Ruiz
During the following "quiet" period in October, the hydrothermal component of the vapor discharge steadily increased. The gases were super-saturated with elemental sulfur; their thermodynamic equilibration temperatures can range from 200 to 600° Celsius. Gases and water from fumaroles and thermal springs on the flanks of the volcano are likely to be produced from a two-phase vapor-brine envelope adjoining the eruptive system within the volcano. The chemistry of the fumarole discharges is compatible with the comparison of an eruptive mechanism involving the build-up of pressure in an extensive vapor zone by gas released from a stagnant, already extensively degassed body of magmatic material at depth. Production of such a residual gas over extended periods may account for the large amount of sulfur dioxide (SO2) being released from the volcano in relation to the small amount of ejected solids.