Really "old" water

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Posted by Ballpark Frank ( on 11:55:40 08/06/16

In Reply to: Question about Old Faithful posted by Jessica Carleton


There is a curious phenomenon that we see regarding the age of the water in geyser fields. Geologists have measured the amount of tritium in geyser water, and determined that the water exiting geysers has been in the plumbing system for hundreds of years. I have seen information sources quoting anywhere from as recent as 300 years to as long as 2,000, but the most recent info seems to indicate a subsurface time of around 500 years. Without getting into the technical detail involving protons and neurons, tritium is a type of water that decays at a predictable rate, so it lends itself to "aging" water that has been underground for a lengthy time.

We know that groundwater is the general source for geyser water, but that water could be the result of leakage from lakes and rivers, rainfall, snowfall, or even leaky plumbing in the buildings at the Old Faithful developed area. With the tritium findings, we know it takes a long time for water derived from the surface to make its way deep enough to enter a particular geyser's plumbing system.

The fact that virtually all Yellowstone's geyser fields are found in close proximity to flowing creeks/rivers and even lakes (Shoshone and West Thumb) is noteworthy.

Now, if we look at where the water exiting the features at Mammoth come from, it's a whole different story, and the story keeps changing over time.

We know that some percentage of the thermal fluid emerging in Mammoth's springs and contributing to its distinctive terraces comes from the Norris area via some sort of subsurface "conduit" system. Over the years, as research tools and methods have improved, the percentage of Norris contribution has steadily decreased to the point where the last figure I remember seeing was down around 7-10%. There are numerous unproven theories about where the rest of the water originates. We know that Mammoth is a long ways north of the caldera, which is why we rarely see thermal water temperatures above 160-170F. That, and the absence of silica-rich ground to create pressure-resistant plumbing is why we don't see geysers at Mammoth.


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