On the very northern end of Owens Valley in California, along a section of River known
as Hot Creek, steam, sulfur dioxide, carbon dioxide, and other gasses emerge from small
holes in the ground.
At one site, these vents known as fumaroles are highly clustered, with a dozen vents occurring
next to each other.
Additionally, unusually warm and in some cases near boiling point water emerges at hot springs,
in rare cases even causing small geysers to form.
Although the rest of the seemingly flat basin between two mountain ranges might not seem
all that suspicious, it represents the rim of a still potentially active supervolcano
known as the Long Valley Caldera.
Underneath the aforementioned geothermal site, known as the Hot Creek Geologic Site, you
can find magma at fairly shallow depths of only 3 miles or 5 kilometers.
This molten rock provides the heat source and volcanic gas which is emitted at all of
these regional geothermal features.
Yet, this group of features which is part of the Long Valley Caldera supervolcano is
once again in the news.
As, sometime in early June of 2023, frequent visitors to this site reported something unusual.
At a white and altered patch of ground which was beforehand barren of any water, now there
was a 5 foot wide and 20 foot long hole in the ground which was several feet deep.
This depression was filled with unusually colored non blue water which was clearly heated
to a high degree, resulting in the water vigorously steaming.
What had just occurred was the formation of a brand new hot spring.
This feature would go on to produce small geysers of water on occasion, but this was
only temporary.
Once the presumably acidic heated water being supplied into this so far unnamed hot spring
carved away a wider pathway to travel into, the geysering activity ceased.
So, does the formation of this hot spring indicate anything unusual at the wider volcano?
The quick answer is no, it does not.
The Long Valley supervolcano currently contains at least 1,000 cubic kilometers of magma at
depth, which is around 27% melt aka active liquid by volume.
This melt fraction is considered lower than the 35 to 50% melt a volcano generally needs
to be theoretically capable of producing a volcanic eruption in the first place.
Yet, it ranks highest among the 3 potentially active supervolcanoes in the United States,
ahead of the Valles Caldera with 17 to 22% melt and Yellowstone with 5 to 15% melt.
Despite all of this magma, for now it is quite likely to remain fairly stationary, meaning
the development of a new geothermal feature does have any larger meaning.
As, at fairly large geothermal sites, new vents regularly disappear and appear, while
others change in intensity, size, or even sometimes move in position slightly.
This is because the heated water regularly carries with it dissolved minerals, which
upon cooling can be deposited either on the surface or in the conduit pathway to the surface
geothermal features.
What this means in the long run is that as minerals such as calcite in the water rise
to the surface precipitate, they form a crystalline wall which can sometimes completely block
the pathway to the surface.
This causes a surface feature to sometimes disappear and then reappear at a new location,
after a new weak point path of least resistance is found by the water.
The exact pathway the water takes might take as many as several centuries to 1,000 years,
first originating from snow melt and rainfall on mountains to the east and west of Long
Valley.
Eventually, the water seeps into the ground, reaching a fairly deep depth.
It is then heated as underlying magma heats overlying rock, and eventually this heat transfers
to the water.
The water then rises to the surface, along with some volcanic gasses, reaching the surface
via what is known as a hot spring.
Another example of a fairly recent new geothermal feature which formed occurred at the Yellowstone
volcano west of West Tern Lake in Wyoming.
What was previously a healthy hillside began to die, the dead area expanded, and soon white
patches largely from travertine appeared in this dead zone's center along with patches
of ground heated to more than 150 degrees Fahrenheit.
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