posted on Jan, 2 2009 @ 03:19 PM
Hi there,
I've been reviewing this post over the last few days and I encountered a very interesting article:
images.google.com...://quake.wr.usgs.gov/research/deformation/modeling/papers/yellowstone98/yell_fig1_big.gif&imgrefurl=http://
quake.usgs.gov/research/deformation/modeling/papers/yellowstone98.html&usg=__-RTdjeQcoSBNeqyOdDS7uIUMhDU=&h=893&w=805&sz=315&hl=en&start=99&sig2=kEJ1H
fY-D2ejYL1RpB58Yg&tbnid=zobY-dJudgCzEM:&tbnh=146&tbnw=132&ei=83JeSYaFIIb-MtO8hPIK&prev=/images%3Fq%3Dyellowstone%2Bcaldera%26start%3D80%26gbv%3D2%26nd
sp%3D20%26hl%3Den%26sa%3DN
In it there is a description of the interplay of fluid between the two domes (Sour Creek and Mallard Lake) above the yellowstone caldera. What I find
interesting is that it appears there may have been a sort of "release valve" for pressure at the northwest corner of the caldera between 1985 and
1995 when earthquake swarms opened this valve in 1985 then possibly closed it again in 1995. Since then there has been a complex interplay of
repressurization, particularly in the Sour Creek Dome.
What's even more interesting is that it appears that the USGS has named a rough line running between Mount Washburn down along the northeast edge of
the Yellowstone Lake as the "leveling line" underwhich pressure is equalized between the Sour Creek (SC) and Mallard Lake (ML) domes. I'm guessing
the leveling line is an area of dense, hard rock that is particularly resistant to uplift. The uplift occurs on either side of this leveling line
which is why there are two domes.
It also appears that the Mary Lake (YMR) helicorder lies right over top a "conduit" (as mentioned in the linked article, a sort of pipe that is
funneling fluids between the two domes in primarily the SC to ML direction). This conduit only opens when pressure has reached Pc (critical pressure)
in the SC dome. This may be why we are seeing these harmonic earthquakes as they might be recording the flow in this newly opened conduit between SC
and ML. This "conduit" runs roughly perpendicular to the leveling line and what is even more disconcerting is that the earthquakes appear to be
following a track along this "leveling line." What this means, that the earthquakes appear to be following this leveling line, I do not know. What
I do know is that in 1985 and 1995 the earthquake swarms were located at the edge of the caldera indicating a pressure release into the surrounding
bedrock. This earthquake swarm is occuring within the caldera, in a line of rock that has separated and maintained the pressurized domes of the
caldera.
What I'm trying to get at here is that there appears to have been a closure of a "release valve" to the northwest of the park that once allowed
depressurization of the domes and subsequent subsidence. There also now appears to have been a large enough repressurization that a previously closed
conduit between SC and ML has now reopened (as inferred by the harmonic tremors detected at YMR) indicating a high level of magmatic (OR hydrothermic)
pressurization at least within the SC dome. And last but not least it appears that the leveling line is now beginning to crack, possibly due to the
pressure along the SC/ML conduit. I think if you continue to watch the earthquakes over the next few days, you will see that they will continue
northward and begin to drift west along the leveling line as fluid continues to flow between SC and ML.
Again, what this all means, I'd hate to even guess. But it certainly appears that the SC dome is alleviating pressure by transferring pressurized
fluid to the ML dome. In the past the ML dome has relieved its pressurization by "leaking" into the bedrock to the north of the caldera. It's
unclear from what I've seen what the cracking along the leveling line may mean or where the ML pressure might end up going. Any thoughts?