[Geysers] Oscillating pairs of springs/geysers

[Ronald Keam]

This phenomenon on a grand scale, both in time and space, occurs at Waimangu, New Zealand. For more than sixty years the hot lakelet in Inferno Crater has had a quasi-cyclic behaviour of rising and falling over a range which has been as much as ten metres, with an overflow being the usual culmination of the rise (the overflow often being immediately preceded by oscillations of level over a range of about a metre).  When both this and the overflow of neighbouring Frying Pan Lake were monitored from the early 1970s it was discovered that the overflow from Frying Pan Lake was reduced when the level of Inferno Crater lakelet was rising, and increased when the latter was sinking.

Without going into all the details a simplified model of this linked behaviour has been proposed.  Firstly it is clear that a fluid connection must exist between the supplies to the two lakelets.  This might be largely liquid, but some part of it must for some of the time be just steam because the two lake surface levels are usually quite different.  It is believed that strong subterranean boiling occurs within the plumbing beneath Inferno Crater, but that at the end of a main overflow the steam-filled region collapses (i.e. it is the end of the eruption of a submerged geyser at the bottom of Inferno Crater lakelet).  The connection between the two lakelets at this stage becomes a dominantly liquid link and the water starts to drain out through the main vent in the bottom of Inferno Crater lakelet.  From the instant the steam bubble is eliminated the Inferno Crater lakelet provides a suddenly increased hydrostatic (actually hydrodynamic) pressure throughout the fluid connection.  It is this increase that, applied via the linkage at the vents beneath Frying Pan Lake, results in an increased inflow into this lakelet, and hence to its increased surface outflow.  The period of this behaviour is usually around six weeks.

For any reader who has a copy of GOSA Transactions Volume VII the article starting on p.183 could provide other interesting information about the features at Waimangu.

Ron Keam
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Reading through "Geyser of Yellowstone" yet again, the description of Bead Geyser & "Terracette Spring" caught my eye. Evidently when water levels in Bead fall, "Terracette Spring" rises a few inches. Do these oscillate periodically, or chaotically? In a similar fashion when Steamboat erupts Cistern Spring can drop very deeply. What are some other common examples of this synchronicity between two or more features? Are many of these periodic pairs? At one point I developed a model that showed some of these behaviors, (in an attempt to understand Cistern Spring), but it confused me and I moved on... now I'm curious again?

So... favorite periodic pairs, with oscillation periods if known?

--
Brian Davis
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