In the United States there is a looming yet often forgotten geologic hazard, that could effect any
number of millions of people spread across 7 states. While the lower 48's 47 active volcanoes
are for the most part, fairly well known, this is not what this video is about. It is true that
since the end of the last ice age that an active volcano has erupted about once every 51 years in
the lower 48, with these being the last 10 such eruptions. Yet, volcanic eruptions are
in fact more common than this once in every 51 year figure might lead people to believe. As,
there are also 3 dozen other volcanoes that many metrics incorrectly exclude. These are
the nation's dormant volcanoes, which have not erupted at any point in the last 11,650 years,
but are likely to erupt again at some point in the future. Because this is a fairly arbitrary
cut-off, many volcanoes are left out of the "active" list despite the fact that they are
one day likely to erupt again. For example, take the Cima Lava Field in a remote southerneastern
section of California's Mojave desert. This volcanic field has been intermittently erupting
during three phases since 7.6 million years ago. This volcanic center is by all metrics
quite dormant, with no fumaroles, no hot springs, no carbon dioxide emissions, and no suspicious
earthquake swarms. And yet, it erupted twice geologically recently, with one cone erupting
28,000 years ago and another just missing the active volcano cutoff as this half a square
mile lava flow erupted only 11,800 years ago. Due to the rate of eruptions at this volcano,
which can sometimes occur as little as once every 200,000 years, the Cima Lava Field
could unexpectedly erupt again at a point in the future, sending lava flows into the barren desert.
Yet, not all of these dormant volcanoes are located in sparsely populated regions.
For example, California's Big Pine volcanic field which last erupted 16,700 years ago could in the
future threaten the 1,300 person city of Big Pine. Or, in Utah, nearly 20,000 people live
right next to the edge of a lava flow in the Santa Clara volcanic field which last erupted
27,000 years ago. But, the most populated region which has some form of a volcanic hazard adjacent
to a dormant volcano, despite being fairly small, is the majority of the Portland metropolitan area.
Here, scattered remnants of cinder cones, lava flows, and shield volcanoes can be found popping
above the dense suburbs, being part of 80 vents which have erupted during the last
2.6 million years in what is known as the Boring volcanic field. Eruptions here have occurred an
average of once every 32,500 years, with the last eruption forming Beacon Rock 57,000 years ago.
Of these 36 dormant volcanoes in the lower 48 states, here are the 10 with the highest
population living in close proximity to them. Here is a quick overview of these dormant
volcanoes, 16 of which exist in California, 8 of which exist in Oregon,
4 in Idaho, 4 in Nevada, 2 in New Mexico, 1 in Washington state, and 1 in Utah.
If any of these 36 dormant volcanoes were to erupt again, there likely wouldn't be any warning signs
of what was about to begin with gas rising from the ground in addition to earthquakes until a
few weeks to years before an eruption commenses. Otherwise, these complexes would show no obvious
signs of life. While the chance that any one of these complexes might erupt seems fairly low,
with yearly eruption odds for individual systems ranging from 1 in 11,500 to 1 in 900,000
each year, when they are all combined these odds really do add up. In total, the odds
that a currently dormant volcano in the lower 48 U.S. states will erupt each year is 1 in 849. This
means that when factoring the rate of eruptions of active volcanoes in the same space, the yearly
chance of a single volcanic eruption occurring in the lower 48 is not 1 in 51 but instead 1 in 48.
While such a small chance might seem too minimal too be concerned with, in the lower 48 we have 6
examples in the last 5,000 years where volcanoes that had previously not erupted for an 11,650
year long timespan beforehand all of a sudden erupted, meaning they switched from a dormant
to active status, which are shown here. The most recent example occurred at the Black Rock Desert
volcanic field, which in 1200 CE, had not erupted for 13,200 years. Yet, it ended up erupting around
1,200 CE, creating the Ice Springs lava flow. This rate of dormant volcanoes becoming active
seemingly matches the rate I just calculated. While it is unknown which of these 36 volcanoes
will be the next to gain the active status, statistics suggest that at least one of these
volcanoes will erupt before the year 3,000. As a final note, I would like to thank this
channel's patrons on Patreon and channel members on YouTube.