In the United States, many of the nation's most active volcanoes are located in the Cascade
Mountain Range.
In the 20th century, two of these produced volcanic eruptions, Mount Saint Helens in
Washington State and Lassen Peak in California.
However, this area wasn't always the most volcanically active part of the country.
Approximately 950 years ago there was a strange influx of numerous volcanic eruptions in an
area not typically associated with volcanic activity, Utah and Arizona.
Around 1065 AD, 3 volcanoes spread across a geologically similar area may have simultaneously
erupted, with a 4th volcano in the region erupting soon after.
This is quite strange, given that the volcanoes in question are characterized by highly infrequent
volcanic eruptions, ranging in frequency from eruptions about once every 4,700 years to
eruptions every 12,000 years.
The odds of this being a natural occurrence are quite low at 1 in 23,101.
So, what caused a group of rather inactive volcanoes to suddenly all produce explosive
eruptions during this timespan, which was witnessed by many Native American groups?
Could a similar series of events happen again?
This video will discuss this scientific mystery and answer these two questions.
In 1065 AD, a large volcanic eruption began in the vicinity of the modern day town of
Flagstaff in northern Arizona.
After a series of explosions witnessed by the indigenous Sinagua peoples, a group of
towering lava fountains were erupted along a volcanic fissure.
Soon, a large cinder cone was constructed, although the eruption mysteriously became
more explosive over time.
Later, a sub-plinian phase began, which sent a plume of ash more than 65,000 feet or 20
kilometers into the atmosphere.
Once the eruption had ended, the cinder cone built measusured 1,115 feet or 339 meters
tall.
This eruption was unusually explosive, rating in size as about 28% as explosive at the 1980
eruption of Mount Saint Helens.
Yet, its magma was basaltic, and cinder cone forming eruptions are typically not this explosive.
Mysteriously, this eruption may have occurred at the same time as another young volcanic
eruption in Arizona at the Grand Canyon, whose margin of error overlaps with this date.
A third eruption in Utah which produced a several hundred foot tall blocky lava flow
also surprisingly overlaps with this date.
Thus, these three unusual eruptions may have been triggered by a singular event.
Geologically speaking, these three volcanoes are located on the edge of two areas; the
Basin and Range province to the west and the Colorado Plateau to the east.
This area contains an abundance of long geologic faults, which gives one hint at to what may
have caused these near simultaneous eruptions.
Although it is still largely debated, there is a weak albeit ever present connection between
large earthquakes and volcanic eruptions within the next 48 months.
Approximately 1 in 3 Cascade Mountain range volcanic eruptions can be directly traced
to within the margin of error of a large megathrust earthquake as an example.
In the case of the western Colorado Plateau, several large fault lines exist in the area
which are capable of generating magnitude 7 earthquakes.
Two of these large active faults happen to be alongside one of the volcanoes which erupted,
on the north rim of the Grand Canyon.
There, the Toroweap Fault to the east and the Hurricane fault to the west encompass
the boundary of the Uinkaret Volcanic Field.
It is known that these faults produce up to magnitude 7.5 earthquakes every 1,000 to 10,000
years, at least one of which occurred in the last 10,000 years.
Thus, I postulate that a large magnitude earthquake somewhere in southwest Utah or northwest Arizona
occurred around 950 years ago, which led to the eruption of three distant volcanoes.
These volcanoes may have experienced magma mixing, leading to unusual characteristic
eruptions.
Thus, if the true cause really was a large earthquake, such a repeat in activity could
occur once again in the future, albeit an unlikely possibility.
With this being said, this apparent uptick in volcanic eruptions may truly just be an
interesting coincidence.
One of the most important phrases in science is "I don't know" and this is one of those
cases.
Although an interesting possibility, the earthquake hypothesis remains unproven, along with the
exact cause of this unique geologic mystery.
I hope that you enjoyed this video.
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