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Roger Weller, geology instructor regional geology planetary gems
Red Mountain Volcano In The San Francisco Volcano Field, Arizona.
History of San Francisco Volcano Field
The San Francisco Volcano field is an area in northern Arizona, north of flagstaff, Arizona. The field covers about 1,800 square miles of the southern boundary of the Colorado Plateau.
This field has about 600 volcanos, some are 6 million years old
to less than 1,000 years old.
Sunset crater is the youngest. The
highest peak in this field is Humphreys Peak and is Arizona’s highest peak which
towers at 12,633. Humphreys Peak is part of the San Francisco Peaks, an
extinct stratovolcano complex. However, we are going toexplore Red
Mountain Volcano, and is one of the Volcano’s in the field.
Red Mountain is a cinder cone Volcano in the
San Francisco Volcano field, about 25 miles northwest of Flagstaff, Arizona.
Red Mountain volcano is not your usual cinder cone, because it lacks the
symmetry of most cinder cones. Instead this volcano has a u-shape to it,
and has a pretty cool Amphitheater that cuts into its cinder cone. Also,
it has these really neat erosional pillars called “hoodoos” that are all over
the inside of the Amphitheater. Red Mountain rises about 1,000 ft. above
sea level, and is about 740,000 years old. Red mountain is thought to be an
Red Mountain, is one of hundreds of
cinder cone volcanos in an area of 50 miles, and is an amazing place to visit
with the inside exposed which is unusual. It is not like most cinder cone
volcanos in the San Francisco Volcanic Field. Because erosion has not had
enough time to expose their internal features.
Right by Red Mountain is a large
Forest Service sign along highway 180 invites motorist to stop and visit the
cinder cone. From the parking lot it is about a quarter mile off the
highway. From the parking lot it is just a 30-minute or so walk bring you
to the entrance of the amphitheater carved right into the flank of Red Mountain.
The Back wall of the amphitheater is about an 800-foot cliff, which goes down
slope to the left and right. Standing inside of the amphitheater, you are
surrounded by the towering cliffs of cinder, one would think that they were in
the middle of the volcano, however the center of the eruption is over on the
The back wall of the amphitheater seen above is a feature that formed after the eruption and is still being enlarged by erosion today.
A cinder cone forms when the eruption
happens on flat ground, deep in the earth, magma with gases (like a soda pop
drink) rise throw a straight up and down pipe-shaped conduit like a fountain of
gassy lava that can shoot up as high as an amazing 2,000 feet into the sky.
As theses blobs of gassy molten rock fly
through the sky, they cool fast enough to solidify before coming back down to
earth. A lot of gas stay in the fragments. These small fragments are
called" cinders". If the fragments are big, they are called volcanic
bombs. As the volcano continues to erupt these cinders, they pile up to
form conical hills.
Sometimes the sides of the growing hill
become too steep causing the cinders to slide downwards. When the lava fountain
ends, a balanced cone-shaped hill, indented by the cater, will be added to the
landscape. Inside the cone is a pile of loose cinders in layers that dip
away from the vent of the volcano on all sides.
In the last stages of the eruption, the
magma loses most of its gas content. Then when the gas is almost gone the
fountain stop and a type of quite oozing runs into the cater or beneath the base
of the cone as lava. Here is a picture of the Red Mountain lava flow and
it is a large field.
My Visit to Red Mountain
When my wife and I visited Red mountain volcano I was in awe, and
had never seen a Volcano up close. Walking up to the volcano did not seem
like much to me, however the closer we got to the volcano the picture stared to
unfold. I could not believe what I was seeing. The ground was full of
black rocks of obsidian, clear quartz, pink quartz, and green olivine. The trail
is about 1.5 miles a very easy hike despite the elevation change from (6,745 to
7,200 feet). I remember walking along the path leading to the crater of
the volcano, and all around was trees and bushes and suddenly everything
changed. My wife and I walked into this type of valley and the side
started out gradually and kept getting taller the ground was solid rock. I
know now this was lava, hardly any trees the lava was rough very rough. You
could cut yourself easily on the rough ground. It seemed like I was
walking into a very different world all at once.
The scenery was the most amazing thing I had ever seen in my
life. We had to climb the small set of steps that are shown in the picture
(above) and the landscape changed even more. The funny part is my wife and
I had just left the Grand Canyon, and I thought Red Mountain was way better.
Then we got to the crater of Red mountain and now there was nothing around me
but solid rock. There was are these “hoodoos” all around me 10-20 feet
tall all around me.
I found it also wonderful how life could happen here trees and shrubs growing here as well. It is not hard to spend hours inside Red Mountain walking around looking at all the formations.
Before I conclude please remember to go prepared, Arizona is not
the place to go hiking without bringing plenty of water the climate is dry, and
humidity is low. It is easy to get dehydrated. Bring some snacks as
you will get hungry. One more thing there is no cell phone service at, or
inside of Red Mountain.