If you look around central Idaho, you can see several recent lava fields representative
of volcanoes which recently erupted in the state.
Of these, the most recent eruption occurred at the Craters of the Moon volcano in 130
BC.
With this being said, due to the relatively peaceful nature of the volcanoes which formed
these lava fields, none of them could be truly classified as producing an explosive eruption.
However, there exists a fifth volcano within Idaho that few are aware of, which produced
an eruption equivalent in size to the 1980 eruption of Mount Saint Helens only 10,000
years ago.
The volcano which produced this massive eruption is called Menan Buttes, which could eventually
erupt again.
The Menan Buttes volcano is located in eastern Idaho, where it lies only 20 miles north of
the city of Idaho Falls.
At first glance, you might think the volcano you are looking at is a series of two medium
sized volcanic vents referred to as cinder cones.
However, there are two problems with the previous statement.
First, these vents are not cinder cones, but rather an unusual type of vent called a tuff
cone, which are formed by highly explosive eruptions with very little lava.
Second, these are not two vents, but rather three.
There is the North Menan Butte, the South Menan Butte, and a rather hidden Central Menan
Butte in the middle.
If you zoom in, you can make out the gently raised rim of its Central Menan Butte's edifice.
So, how did these three vents form?
10,000 years ago, a volume of low silica basaltic magma began pushing through the crust in this
section of Idaho.
As this magma rose to the surface, it generated a series of earthquakes which got shallower
and shallower.
Eventually, this magma began to interact with the freshwater in the adjacent Henry's Fork
River and Snake River.
This heat from the rising magma caused much of the water in a section of these rivers
to rapidly flash to steam.
Eventually, the volume of steam became too great, and the ground exploded upwards in
a massive eruption.
As a tall plume of ash was carried high into the atmosphere, superheated gasses from this
explosion raced outwards in every direction.
These gasses created a series of pyroclastic flows, which traveled up to 8 miles away.
Concurrently, as much of the rock ejected by this massive explosion fell back to the
ground, it began largely filling the massive crater created by this explosion.
This material also fell on the crater rim, thus building a volcanic cone called a "tuff
cone".
At the time, the wind was blowing strongly to the northeast, causing this tuff ring to
be created with an elongated shape in that direction.
By the time this individual eruption was over, a massive 10,000 foot wide and 745 foot tall
tuff cone has been created.
In total, this explosion ejected an impressive 700,000,000 cubic meters of volcanic rock.
However, the eruptive series had not ended.
Not long after this eruption took place, perhaps within a few minutes, a second explosion occurred.
This second explosion began at a much greater depth compared to the prior eruption.
As a result, this explosion formed only a relatively flat and hidden tuff ring.
The outline of this tuff ring is shown on screen, which is largely overlapped by two
crop circles.
The third explosion was more energetic than the second one, and was caused by close interaction
with the snake river.
As the ground exploded upwards once again, another large tuff cone was created.
This tuff cone measured 8900 feet wide and 552 feet tall.
The eruptive sequence which had just occurred likely took place within a span of a single
hour.
In total, 1 cubic kilometer of tephra and ash was ejected, meaning this eruption was
exactly equivalent in size to the 1980 eruption of Mount Saint Helens.
Although no more eruptions have occurred since, this unique volcano's existence proves that
another highly explosive eruption could occur in the future.
Such a future eruption would be catastrophic, as debris and pyroclastic flows from such
an explosion could reach up to 15 miles away, even the northern outskirts of Idaho falls.
Luckily, the odds of such a future eruption are quite low, as this volcano may only be
capable of a single eruption.
Using the US geological survey method of rating volcanoes, Menan Buttes would be classified
as a moderate threat volcano.
This would make it the highest threat volcano within Idaho, although the age of its formation
is still up for debate.
I hope that you enjoyed this video!
If you would like to request a specific topic, please leave a comment below!
Additionally, if you wish to support this channel, consider becoming a patron on patreon.