Statistically speaking, California is the third most likely state in the lower 48 U.S.
states to produce the next volcanic eruption.
As, the state contains 11 active volcanoes, the most recent of which to produce a volcanic
eruption was Lassen Peak in 1917.
These active volcanoes can be found across much of the state, ranging from the below
sea level Salton Buttes volcano, the Ubehebe Craters in Death Valley National Park, to
the towering glacier covered volcano that is Mount Shasta.
Yet, these are not the only volcanoes within California which might one day erupt again.
As, there are also a series of dormant volcanoes which have erupted at some point in the last
100,000 years but have not erupted during the Holocene period which began 11,650 years
ago.
One such volcanic field that encompasses a wide range of vents can be found within Owens
Valley, and is generally not well known despite being fairly obvious.
There, in what is known as the Big Pine Volcanic Field, a series of more than two dozen cinder
cones and one lava dome can be found alongside black colored lava flows which stretch to
the east and west of U.S. Route 395.
One of these cinder cones that occurs on a hillside is associated with what looks like
an especially fresh looking lava flow, as it originated only 16,700 years ago.
In total, there are approximately 40 vents which have erupted intermittently across a
timespan of 1.3 million years ago to 16,700 years ago.
Based on this figure, we can get an average rate of eruptions being about once every 32,500
years.
Luckily, there is some good news.
Eruptions in this volcanic field seem to be somewhat but not completely constrained to
a 10,000 year period following a glacial maximum during the most recent ice age, and with the
last glacial maximum being 21,000 years ago the chance of another volcanic eruption in
the near future is fairly low here.
With this being said, why does the Big Pine Volcanic Field exist in the first place?
As we zoom out from Owens Valley, we can see a series of mountain ranges which trend in
a north-northwest to south-southeast orientation.
These repeat over and over and inbetween them have valleys, with the overall region being
at the very western edge of the Basin and Range Province.
Here, the crust is slowly spreading apart to the east and west, creating large swaths
of terrain which largely look the same.
This extension creates a series of large fault lines in the crust, creating uplifted patches
of land known as horsts and subsided patches of ground known as grabens.
This process created a significant number of faults.
Upwelling mantle material then used these faults as a path of least resistance, creating
magmatic intrusions some of which eventually erupted onto the surface, forming scattered
volcanic fields.
The Big Pine Volcanic Field is thus bordered by several major fault lines which have controlled
where eruptions could occur.
The first volcanic eruption occurred 1.3 million years ago when a volume of magma intruded
into the crust northwest of Independence California.
Eventually reaching the surface, a series of phreatic explosions occurred, which then
transitioned into vigorous lava fountaining.
Strombolian explosion subsequently occurred which ejected moderate amounts of ash, and
a lava flow travelled several miles before the eruption ended.
A similar process would repeat over the course of this field's lifespan, forming 40 cinder
cones which ranged anywhere from 50 to 720 feet in height.
One batch of magma remained in the crust for some time, eventually evolving into rhyolite
which then explosively erupted and formed a 1.1 mile long lava dome approximately 1
million years ago.
The largest single feature in the volcanic field which could be described as either a
small shield volcano or large cinder cone is known as Crater Mountain and over the course
of a potentially 18 month long eruption 300,000 years ago covered 11.7 square miles in more
than 30 feet of basalt lava.
More bursts with several eruptions in a relatively brief timespan occurred 300,000 years ago,
130,000 years ago, and most recently 17,000 years ago.
3 such moderately explosive eruptions between 16,700 and 17,400 years ago which deposited
up to 5 mile long lava flows represent the most recent volcanism in the Big Pine Volcanic
Field.
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