Kieran D. O’Hara ¹*, E.K. Esawi ²

1 Dept. of Earth and Environmental Sciences (emeritus) University of Kentucky, Lexington, Kentucky 40506, USA
2 Division of Physical Sciences, Elizabethtown Community & Technical College, Elizabethtown, Kentucky 42701, USA

Abstract

A physical model of the Old Faithful geyser successfully replicates the eruption interval for the years 2000–2011. It is based on convective boiling in the conduit in three stages, and the model is in good agreement with published time-temperature-depth data. The preplay phase, which triggers the main eruption, displays a Rayleigh probability density function with a mode at nine minutes, and it plays an essential role in determining the main eruption interval. It is assumed that temperature gradients are small due to convection, and individual convection cells can be assigned a single heat content. Based on previous observations and drill-hole measurements, the bottom heating and recharge temperatures are assumed to be 110 °C and 80 °C, respectively, and the total volume of the cylindrical conduit is 23 m3. A prescription for both short and long eruption intervals is

eruption interval = (time to boiling of upper stage) + (preplay time).

A composite model reproduces the bimodal eruption pattern in which long eruption durations are followed by long eruption intervals and short eruption durations are followed by short eruption intervals. The cause of short eruption durations is not addressed and remains unresolved.

Manuscript received 18 Nov. 2012; accepted 28 Feb. 2013

DOI: 10.1130/GSATG166A.1