[Geysers] Excelsior & GPS

[Ron Keam]

A contrast with two New Zealand examples of high discharge thermal 
springs might be of interest:

When Waimangu Geyser was active (1900 - 1904) the water in its basin, 
between eruptions, would have stood about 9 metres below the level of 
neighbouring Inferno Crater lakelet.  In that era Inferno Crater 
lakelet overflowed for most of the time, but it used to recede 
gradually perhaps ten centimetres some time after the geyser 
commenced playing.  The geyser's active interval would generally last 
for several hours, and its period was about 30 hours.  A few hours 
after the geyser ceased playing Inferno Crater lakelet would 
recommence discharging and continue to do so until after the next 
eruption commenced.  The horizontal separation between the site of 
the vent of Waimangu Geyser and the main vent in Inferno Crater is 
about 100 metres.

In recent decades it has been shown that Frying Pan Lake in 
neighbouring Echo Crater at Waimangu has a fluctuating outflow that 
is time-correlated with fluctuations in Inferno Crater lakelet level. 
Unlike when the geyser was active, the recessions in the lakelet are 
now usually to a depth of between 5 and 7 metres below outflow level, 
and the whole cycle takes around six weeks. The discharge from Frying 
Pan Lake is greater than average when water level in Inferno Crater 
is falling, and lower than average  when there are discharges 
occurring from Inferno Crater. The horizontal separation between the 
main vent of Frying Pan Lake and the main vent of Inferno Cfrater 
lakelet is about 400 metres.

Ron Keam

>Bruce Jensen & I were having a discussion about Excelsior and Grand 
>Prismatic Spring, and came up with two question I couldn't answer 
>(so I thought I'd ask here). First, did Grand Prismatic Spring have 
>any response to eruptions of Excelsior? It seems remarkable if it 
>didn't have some response such as decreased flow or at least 
>temporary level changes, but I've been unable to find anything on 
>this. Second, are there other examples of such high flow volume 
>features with such significantly different hydrostatic levels 
>located this close to each other (and what is that due to - very 
>different hydraulic conductivities, i.e., one has significantly 
>greater hydraulic "friction" than the other)?
>
>--
>Brian Davis
>
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Ron Keam
The Physics Department
The University of Auckland
Private Bag 92-019
Auckland
New Zealand
Phone +64 9 373-7599 extension 87931
FAX +64 9 373-7445
EMail r.keam at auckland.ac.nz
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