New Mexico is home to numerous volcanoes and intrusive igneous features from the distant
past and geologically recent past.
This includes four active or potentially active volcanoes, per the U.S. Geological Survey,
with 3 of these 4 volcanoes having erupted at some point since the end of the last ice
age 11,650 years ago.
Yet, these 4 volcanic complexes do not represent the only systems which could one day erupt
again.
As, the state also has two additional volcanoes which are dormant, as they have a much longer
average interval between two volcanic eruptions than the 11,650 year cut off.
Thus, I present the Raton Clayton volcanic field which produced two eruptions between
44,000 and 55,000 years ago, one of which formed the Capulin cinder cone.
However, there is also another and even younger volcanic field which partially straddles the
border with Mexico.
Known as the Potrillo volcanic field, it encompasses more than 100 vents, including a 5420 foot
wide and 140 foot deep explosion crater that formed in an explosive volcanic eruption only
16,000 years ago.
Although this feature known as "Hunt's Hole" will not specifically erupt again, new vents
are likely to one day form in the same field as the Potrillo complex has recently erupted
about once every 17,000 years.
However, the most spectacular feature in this volcanic field is the even larger Kilbourne
Hole to the north, which is 12,580 feet long, 9,000 feet wide, and 440 feet deep.
And, within this crater are numerous pieces of Earth's mantle.
What I am referring to are green and greenish yellow crystals known as olivine, with the
gem variety of this mineral being known as peridot.
The larger Kilbourne Hole maar formed when a body of magma originating from the mantle
intruded into the crust approximately 24,000 years ago.
Each of this field's other 6 explosion craters aka maars formed in a similar process albeit
with the others being formed in smaller explosive eruptions.
However, the other 94% of vents in the Potrillo Volcanic Field formed in either mildly explosive
or primarily effusive eruptions.
And here is why this volcanic field exists.
Just like the potentially active Carrizozo volcano to the north-northeast, the Potrillo
volcanic field exists due to a rift zone in the crust known as the Rio Grande rift.
Here, in parts of New Mexico and Colorado, the crust is very slowly spreading apart to
the east and west.
This spreading causes material in the mantle to more easily permeate through the crust,
occasionally reaching the surface and forming a chain of infrequently erupting volcanoes.
Vents in the Potrillo volcanic field generally got older to the west, meaning over the 885,000
year lifespan of this volcanic field, on average vents would get younger to the east.
The first cinder cone formed 885,000 years ago, when a volume of magma erupted onto the
surface, initially producing a series of phreatic explosions.
After this occurred, a series of strombolian eruptions began which ejected bombs of lava
in a 3000 foot radius, sometimes occurring alongside several hundred foot high lava fountains.
As most of the erupted material did not travel very far, bits of tephra and ash mostly piled
up around the active vent, forming a several hundred foot high cinder cone.
Several maars also formed during this period when phreatomagmatic explosions occurred due
to the interaction of intruding magma with groundwater which then flashed to steam and
exploded, generating a large crater.
Frequent eruptions occurred at a rate of about once every 4,000 years for the next 400,000
years, forming numerous cinder cones, some of which produced up to 2.5 mile long lava
flows.
Then, around 480,000 years ago, the rate of eruptions dramatically decreased.
The largest volume eruption in this field occurred approximately 23,000 years ago, when
instead of forming a cinder cone, unusually gas poor lava erupted in an almost completely
effusive manner.
Erupting more than a cubic kilometer of lava over a period of several years, this effusive
eruption created a 150 foot high shield volcano that coated a total of 25 square miles in
a layer of black basaltic lava.
Known as Aden Crater, its summit region contains a series of pit craters that trend to the
east and southeast, suggesting that it once may have contained lava tubes.
This volcanic field has recently appeared to erupt at a rate of about once every 18,000
years, which is in my opinion the odds that it will erupt again each year.
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