[Geysers] Nature Article

[Whitledge, Vicki M.]

The Nature article that we have been hearing about is titled "Uplift,
thermal unrest and magma intrusion at Yellowstone caldera" by Charles W.
Wick, Wayne Thatcher, Daniel Dzurisin and Jerry Svarc and appears in Vol
440 No 2, 2 March 2006 issue of Nature on pages 72-75
 
The cover of this issue of Nature has a picture of Steamboat in steam
phase with the catchy title "ECHO FROM A SUPERVOLCANO  Uplift has a
downside in Yellowstone Park".  As with most catchy titles, it really
doesn't have much to do with the article, but it makes you want to read
it.
 
Most of the article deals with the movements that have been seen in the
surface and hypotheses about what  is causing the movement (i.e. details
of magma flux).  I'm not a geologist, so I won't try to go into those
details, but will just mention some things that caught my attention in
relation to geysers.  I'll be summarizing my understanding of what they
are saying, so if someone notices I messed up, please correct what I
have said.  Everything I mention occurs in the last three paragraphs of
the article.
 
The authors suggest that uplift causes changes in the permeability and
increasing permeability in geyser conduits may increase geyser eruption
frequency.  (They cite Ingebritsen & Rojastaczer "Controls on geyser
periodicity" Science, 262, 889-892, 1993.)
 
They mention the response of geysers to earthquakes...  In Husen,
Taylor, Smith, & Heasler "Changes in geyser eruption behavior and
remotely triggered seismicity in Yellowstone National Park produced by
the 2002 M 7.9 Denali fault earthquake, Alaska" Geology 32, 2004.  (Yes,
"Taylor" is Ralph Taylor)  an increase in geyser activity was noted
after the Denali earthquake produced ~0.5 microstrain of dynamic strain.
The authors of this latest paper calculate that the strain caused by the
observed inflation is an order of magnitude greater (>6 microstrain) but
this strain is applied over 3-4 years.  They think this could have led
to some of the surface manifestations ("accentuated thermal unrest" in
NGB in 2000-2003 and near Nymph Lake).
 
Also of note, the authors make quite clear that thermal disturbances in
NGB are fairly common and that even the stronger disturbance that they
looked at was not unique.  What is different is that deformation was
actually measured during the disturbance mentioned in the article and a
cause-and-effect relationship between the deformation and the
disturbance is suggested.  They further suggest that deformation may
have caused past disturbances but the deformation would have been
undetected.
 
 
 
Vicki Whitledge
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