[Geysers] Pohutu

[Ron Keam]

I will give a partial reply to Kory:

The activities of the New Zealand geysers are not regularly recorded. 
The number of 'geyser gazers' is very small indeed and is confined to 
some of the professional geothermal researchers, and even they would 
probably not class themselves as such in comparison with the sorts of 
investigation and detailed diarising of the activities being 
conducted by observers in Yellowstone National Park.  However, Ashley 
Cody has the best detailed knowledge of activities for individual 
recent years and might be able to provide you with information about 
1994 specifically.  Earlier than that my former PhD student, Jim 
McLeod, was employed to make records for several months at 
Whakarewarewa and deployed instruments for this purpose.  There were 
some studies in connection with the Geothermal Monitoring programme 
set up specifically to study the decline in surface activities that 
resulted from the widespread take of geothermal fluid for domestic 
and light industrial use in Rotorua City.  A less comprehensive 
summary of activities than might appear to be the case concerning the 
Rotorua geothermal system was presented in the paper by Ashley, 
Katherine Luketina, and myself, published in Volume VII of the GOSA 
Transactions, pages 148 - 168, in 2002.  In the early years of the 
twentieth century a caretaker occupied a little hut on a promontory 
overlooking Geyser Flat and he kept regular records of the activities 
during the daylight hours when he was present.  (I have not actually 
seen any of these myself, but I know others who have.)

What I can say is this.  Pohutu, and its directly connected Prince of 
Wales Feathers geyser on the north side, and Te Horu on the south 
side, certainly have related behaviours.  But the activities change 
dramatically, and there is now essentially no 'standard' behaviour 
that persists for years on end.  (You will see aspects of this in our 
Transactions article.)

The Orakeikorako geysers also show changing patterns, and the best 
account of that region is Ted Lloyd's bulletin published in 1972.  I 
have never seen Orakeikorako the same twice when intervals between my 
visits exceeded a few months.

I suspect that in the days before geothermal power development the 
Wairakei Geyser Valley geysers might have been more regular than 
those in most other New Zealand geothermal systems.

It is of course the semi-predictability, yet semi-unpredictability, 
of intense geothermal systems that makes them so intriguing  And this 
characteristic, combined with the unusual and diverse surface 
features and deposits and the associated assemblages of unusual 
vegetation types (and also the microfauna in and around the features) 
makes them very attractive/ gruesome/ fascinating etc.

Note: I am using the term 'intense' to mean those systems with 
geothermal fluids at shallow depths possessing temperatures greater 
than boiling temperature at the ground surface.

Ron Keam


>A message from Kory Collier  20 Dec 2005
>
>In 1994, a flight of mine got unexpectedly re-routed through Auckland with a
>really long layover---long enough to rent a car, drive to Rotorua, spend two
>hours at Whakarewarewa, and get back to the airport in time (a lot of
>driving that day, but well worth it!)
>
>Like Tara, I was very impressed with Pohutu.  If I've read her data
>correctly, the intervals they were there for were all very close to 40
>minutes, and the durations in the 15-20 minute range.
>
>During the two hours I was there in September 1994, the intervals were a lot
>shorter: I think roughly about 5 minutes (I have no idea where my notes from
>that day are now); but I clearly remember that the intervals from start to
>start were in the 10 to 15 minute range---at least the several that I timed.
>   I wasn't always in spots where I could see Pohutu, but as I explored the
>basin, I kept looking over my shoulder at it as much as possible, and it
>never went very long without erupting.
>
>I would love it if any of the New Zealand list readers could tell me (my
>curiosity of eleven years ago has been reawakened) if the short intervals I
>observed were typical for 1994.  If so, for how long of a period of time
>were the intervals typically that short?  Or maybe did Pohutu cycle between
>short intervals and longer ones?  What would be the best resource for me to
>look up what Pohutu's numbers and behavior have been like over the years?
>
>I went there that day with a vague understanding that Pohutu's intervals
>were usually some small number of hours, and I wasn't even sure I should
>hope to see an eruption in my limited amount of time.  So seeing several was
>a real treat.  And the eruptions were indeed beautiful.  From some angles of
>view, the column of water had a slender, nearly perfect shape, and from
>others it gave me a wider, more powerful impression.  It was also amazing to
>me to note how very Yellowstone-like the hot springs appeared in general
>while their setting was very unlike Yellowstone geyser basins.  I guess that
>shouldn't be surprising, but somehow it still struck me as uncanny.  It was
>definitely one of the more fascinating two-hours periods I've ever spent.
>
>Kory Collier
>kory at mstar.net (Note the different address.  For some strange reason I can't
>post to the list using my MSTAR e-mail, but it's the only account I usually
>read.)
>
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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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