THE FIVE VOLCANOES LOOP

North of Flagstaff are five geologically unique cinder volcanoes.  Sunset Crater is the most famous and a national monument. Strawberry Crater is so named for its shape and red color. SP Crater is revered as the classical definition of a cinder cone by geologists.  Colton Crater has a extremely violent past. And last is Red Mountain with a labyrinth of  canyons and hoodoos.

Starting from Flagstaff they are linked by a 105 mile loop of paved and dirt roads.  All of them can be visited in a single day if you don't stop long at every crater.  There are hikes at each that vary in length and difficulty and if you want to do-it-all it would require an overnight dry camp or a two day trip.  It is worth it, the views are spectacular and the night skies dark.

Five Volcanoes Loop

There are parts of the drive that require a high clearance four wheel drive vehicle.  All of the roads are legal and appear on a Coconino National Forest Map except for the 25 mile stretch between Highway 89 and 180, which is outside the national forest boundary.  That section is a checkerboard of state land and private property.  Keep to the established roads and away from ranch houses and all will be good.  Unless you know the country well take a topo map or GPS.  Few, if any, of the dirt roads outside the national forest boundary are marked.

SUNSET CRATER

Summer view of Sunset Crater

Measured from downtown Flagstaff drive 16 miles north on Highway 89 to the park entrance to Sunset Crater.  It is certainly the most famous and beautiful of the five volcanos, but unfortunately with fame comes regulation.  There is a $5 dollar fee payable at the visitors center and hiking is prohibited except on established trails.  It is still worth the price.

I will not go into the geology of Sunset Crater.  At the visitors center is a plethora of information, displays, maps and photos you can look at and read.  I don't feel a need to repeat what they already have.

Sunset Crater is less than a thousand years old and virtually no natural erosion has taken place, but many hikers, including myself in 1962, caused extensive erosion and worn a wide and deep trail into the loose cinders of Sunset Crater.  In 1973 the forest service closed the crater to hiking and spent considerable time and effort filling in the trail and raking out the scared slope.  The only tracks to be seen today are those left behind by deer, elk and bear.  I hiked up a nearby crater to take the photo below and I found bear tracks in the snow.  

 Winter storm clouds approaching Sunset Crater.



There are three trails at Sunset Crater.  The first is a short but rocky path over the Bonito Lava Flow at the View Point pullout.  Directly across the road from the view point parking lot is another trail up Lenox Crater.  It is a strenuous hike 1/3 of a mile to the top where there is  great view of San Francisco Peaks but not Sunset Crater.  Go figure.  The third trail and my favorite is the north and south Lava Trail.  The north trail starts as a sidewalk but it ends and the trail wanders around several volcanic features such as a pressure ridges,  lava caves and a spatter cone you can walk into.  The south Lave Trail is a new 1/4 mile strip of sidewalk that goes to a point overlooking the Bonita Lava Flow, a torturous landscape which still looks freshly erupted and is as jagged and sharp as broken glass. 

On the North Lava Trail

From the South Lava Trail

Looking through the lava along the South Lava Trail.

A tall lava squeeze at the end of the South Lava Trail.

After touring Sunset Crater take the highway towards Wupatki National Monument.  Forest Service Road 546 is on the opposite side of the highway from the Cinder Hills Overlook at the NE boundary of the park.  It is a good two track road of hard packed cinders but beware the loose ones on both sides.  Drive 6.2 miles to the "T" intersection with FS Road 779, which is unmarked.  Turn right at the "T" and it is a rocky 2 miles to Strawberry Crater.  A left turn at the "T" and the road will take you directly back to Highway 89.

View of the San Francisco Peaks from FSR 546.

STRAWBERRY CRATER

Strawberry Crater is a relatively small cinder cone a deep red color with a black veneer on top.  It sort-of looks like a strawberry dipped in chocolate.  There is a parking lot and a 1.8 mile moderately difficult trail that climbs 300 feet up to the saddle, down into the crater and around the volcano.  Wear high top shoes, there are deep cinders inside the cone.

The saddle is the result of a landslide.

If you hike the trail to the right up to the saddle, you will see a perfect example of an event called 'rafting'.  Cinder cones have an eruption sequence which they typically follow; first they erupt cinders because the magma contains a lot of gas in the form of water steam, sulfur compounds and other atmospheric constituents such as oxygen, nitrogen and argon.  The gas expands as it nears the vent hole and ejects the molten rock into the air to build the cinder cone.  Later in the eruption,  magma with less gas from deeper  in the chamber is pushed out as a lava flow.  Often it has enough force that it lifts the lighter more buoyant cinder pile and rafts it away down slope.

The entire north side of Strawberry Crater was rafted away during it's eruption.  The arch at the bottom of the 'V' was part of the rim and the hummocks past it are piles of the cinder cone. There is a fog bank in the distance covering the Little Colorado River Valley.

The arch was a section of the rim that rafted away.

From Strawberry Crater follow the power line maintenance road 9129L north for 7.6 miles to Highway 89 at the Antelope Hills Trading Post.  There are some rocky stretches along the way but they aren't to bad.

Power line road 9129L


Head north on Highway 89 for 3.5 miles to Hanks Trading Post and gas station that has no sign. Turn left on the dirt road south of the building and head west onto the Babbitt Ranch cattle range.

  

Hanks Trading Post

SP CRATER

For the next five miles you are looking directly at SP Crater. When approached from this direction it has a stunning profile with near perfect symmetry. Even though it is 55,000 years old it has stood up to erosion exceptionally well, due in part to its hard cap of welded spatter and low rainfall.  SPC is the classical definition of a cinder cone. I have seen more photos and descriptions of it in geology books than any other volcano.

After 5 miles you should be at the base of SP on the east side.  Follow the road south past a large steel tank and stay right when the road splits.  In 300 yards take the dirt track on the right that goes up the hill to the saddle between on the west side SP and the adjacent cinder cone.  4WD ONLY!  The saddle is the best place to climb SP from.  There are a dozen trails and all are the same.  It's a difficult 400 foot climb straight up a steep, loose cinder slope. Literally, you slide back one step for every two taken forward.  It is rewarding to reach the top but walking the rim is still rough.  It is littered with volcanic debris that want to rock-or-roll when stepped on. 

In spite of its age it has a black lava flow that stands out well enough against the surrounding landscape that it is easily visible from the space shuttle.  It can be seen in the Google Earth view at the beginning of this essay.  The flow crept north for over four miles and two lobes from its western edge spilled into a graben.  A graben is a down dropped strip of land between two parallel faults that forms from stretching of the crust. 

The lava flow with two lobes on the left that poured into a graben.

     

3' long volcanic bomb shaped like a bulls skull.

  

A tunnel through the spatter layer.

The inner crater is deep and dangerous and a pit best to stay out of.  On the sides are thick layers of spatter that appear as steps, each indicating a pause in eruptions.  At the bottom is a large scree pile, not a resurgent dome as one might think.



Inner crater with Kendrick Peak in the distance.


COLTON CRATER

Colton Crater from the flank of SP Crater.  The San Francisco Peaks rise in the background.

Colton Crater is just 2 miles south of SP Crater.  It is easy to spot, just look for the volcano with the gaping maw chewing at the sky.  It reminds me of the mouth of a sand worm emerging from the desert in the Frank Herbert book 'Dune'.

There are two unmarked dirt roads to CC and either will get you there.  On the NNW side of the volcano is a gate through a barbed wire fence and a road that climbs up to the lip of the crater.  It takes four wheel drive to get up it.  Close the gate behind you to keep cattle where they belong and the Babbitt Ranch cowboys happy.


Track up the NNW side.

NASA test drove the Space Exploration Vehicle here in 2008.  Standing on the rim you might notice that this cinder cone is unlike any other you've ever seen.  If you walked the trail into the bowl at Strawberry Crater you almost waded through cinders.  If you trudged up the loose cinders at SP Crater you saw volcanic debris everywhere on top and inside its inner sanctum.  But this is just an empty, massive bowl except for a very small cinder cone in the  bottom.

The strata in the walls are layers of spatter from the original cinder cone.

At the bottom of the crater is a 150 foot tall cinder cone that was a last-gasp effort from the magma chamber. It sputtered for a few days then lost pressure and froze in place. It is partly buried by an alluvial fan washed down from the south wall of the crater.

200,000 years ago Colton Crater was like any of the other cinder cones you see surrounding it.  Then  ground water found it's way through limestone caverns into the magma chamber beneath the volcano.  When the water flashed to steam it expanded 1,700 times exploding with tremendous force.  A few hundred feet of limestone strata under the volcano was pulverized and the cinder cone was catapulted into the sky.  A sizable earthquake radiated out from the site and a pyroclastic mushroom cloud rose into the stratosphere.  As the debris fell back to earth it buried what remained of the cinder cone and the countryside around it.  Chunks of white limestone can be found lying around on the surface and in piles of soil that rodents pushed out of their burrows.

CC has a much larger crater compared to most cinder cones. It is 4,100 feet across and 1,100 feet deep. The bottom of the pit is 250' lower than the surrounding plain outside of the volcano making the crater deeper than the volcano is tall. It is 3 times the diameter of the hole left by the largest nuclear bomb ever detonated on earth and Meteor Crater could nest inside it.

There is no trail around the crater rim but there is a track part way up to the highest point on the south side.  It's a about a mile to the top and a moderately steep hike on packed soil.  The views are wonderful and I found a small geocache at the top in a rock cairn.  You can walk 2.5 miles all the way around the rim but I wouldn't suggest it.  The east rim is rugged and large, loose cinders make the footing treacherous.

The next stretch from Colton Crater to Highway 180 is 19 miles.  It starts as a narrow two track road heading west then veers north past the abandoned Aso Ranch.  After that it turns into a dirt highway for the rest of the way.

Road heading west from Colton Crater.



Aso Ranch

It winds around a bit and other roads intersect it and none of them are marked.  Just stay on the primary road and keep working your way west.  At high points along the way you can see Red Mountain in the distance.  Turn left towards Flagstaff when you reach SR 180 and drive 1.3 miles to the sign to Red Mountain on the right. 

RED MOUNTAIN

It's an easy 1 1/4 mile walk to the volcano.


 The trail to Red Mountain is an easy 1.2 mile walk over flat ground.  Once you climb the wooden staircase you are inside the cone but not the crater. 

The stone wall was laid by ranchers to entrap water.  The staircase was built by the forest service.

The crater is actually on the opposite side of the volcano, but half of it was rafted away 740,000 years ago and  only a drab semi-circular hill remains.  However, the amphitheater you have entered was likely formed by a landslide possibly started by a small steam eruption that blew out one side of the cone. Millennia of erosion carved the towering hoodoos and  the spectacular maze of narrow dead end canyons.  Lying in the stream bed and embedded in the canyon walls are crystals of black amphibole (hornblende) and smoky gray pyroxene.  Both silica minerals formed underground inside the magma chamber and were erupted along with the cinders.  (Bowens Reaction Series).



Red hoodoos

In the slot canyon.



Black hoodoos

 View from the top of the amphitheater.
Not the standard trail and a 700' climb up a 35 degree slope.

The left amphitheater

Cones and...


...pinnacles.

Dizzy drop into the right, main amphitheater.

So ends The Five Volcanoes Loop.  To return to Flagstaff turn right (south) on Highway 180.  It is 32 miles back to town.

WHERE IS THE OAK CREEK FAULT?

The Oak Creek Fault experienced earthquakes on November 25th, 2014 and again on May 5th, 2015.  The quakes were not very powerful, only magnitude 4.7 and 3.5.  Both occurred at night and they woke residents as windows rattled, picture frames fell off  walls and small rocks and trees tumbled down cliffs onto Highway 89A in Oak Creek Canyon.   Little damage was done but it raised awareness and was significant because the Oak Creek Fault has not been active in recorded history.  

After the quakes occurred I started to wonder where the Oak Creek Fault really is, other than the obvious, "Thru Oak Creek Canyon."  On geological maps and Google Earth it is only visible on the surface for 30 miles but it is certainly much longer than what can be seen.  Both ends of the fault are hidden beneath lava flows that have covered it up as it approaches the San Francisco Peaks at the north end, and Verde Valley at the south.  The fault has not moved in several million years or there would be obvious displacement on the lava flows that cover it, which there is not.

So where is the fault? 

Starting at the north end it comes from underneath the San Francisco Peaks, a large stratovolcano that dominates Flagstaff and Northern Arizona.  It then heads south and passes near or under the small mountain community of Baderville at Highway 180 near Snow Bowl Road. 

The fault line is in red.  It is hidden under the mountain and the

soil beneath Baderville so this is just a very approximate location.

 

The fault first appears at the south edge of Baderville where South Snow Bowl Road ends at a shallow canyon.  It then passes between A-1 Mountain and a small parasitic cinder cone next to it.  

  

Baderville at the base of San Francisco Mountain.

Baderville is build on loose sediments that are saturated with water. If the fault ever shakes long and hard the soil will liquefy causing foundations and homes to sink into the ground.

South Snow Bowl Road through Baderville.

From Baderville the fault passes east of A-1 Mountain and heads south towards the I-40 Interstate Highway.

The fault where it crosses Interstate Highway I-40.

Burlington Northern/Santa Fe railroad and the I-40 overpass.

Just south of the I-40 bridges the fault passes under the US Naval Observatory which is built atop a small cinder cone volcano directly over the fault.



The Naval Observatory is a military installation that takes

precise astronomical measurements for global navigation.

Immediately south of the observatory the fault makes its first appearance as Woody Ridge.  This is a 350 foot tall step in the earth caused by fault displacement that continues 10.5 miles to Oak Creek Canyon.  

   

The Flagstaff Arboretum complex lies 1.7 miles 

south of the observatory and next to the fault.  

 

Woody Mountain is another volcano next to the fault line.

   

It lies just 1/4 mile east of the fault. 

Flagstaff's botanical garden of native trees and  plants is also a rehabilitation center for injured birds.  

 

By the time Woody Ridge reaches Oak Creek Canyon it is 700 feet tall. 

At Fry Canyon, a mile north of Oak Creek Canyon, the fault splits into two branches. The platform between the branches is a suspended bench that broke away from the main fault and was left behind as the rest of the fault continued to rise.  Forest Service Road 535 climbs the bench which is a popular camping area in the summer months for large parties and overflow campers from Oak Creek Canyon.

Oak Creek Fault splits and passes to the right and left of the suspended bench.

  

Both branches (1 & 2) of the fault continue on into Oak Creek Canyon where they cross Highway 89A at the Switchbacks. There are eight locations where the two fault lines cross under the highway. Only two (3 & 4) are readily visible. In addition, there are several slump blocks on the steep slope but I show only one (5) that can be easily seen. These are fractured blocks of earth that are slowly slipping down into the canyon.



1.  Oak Creek Fault - the main fault.

2.  Secondary fault branch.

3.  Location where the photo below was taken.

4.  Location where the photo below was taken.

5.  Location of the slump block fracture - photo below.

6.  Viewpoint - elevation 6390' - photo below.

7.  Pumphouse Wash - elevation 5700'.

8.  Oak Creek Canyon and Oak Creek.

9.  Sterling Canyon.



Photo point 3:  The Oak Creek Fault.

On both sides of the fault the rock has been pulverized and a fault zone a hundred feed wide is easily eroded.  On January 23, 2010 record rains and snowfall scoured this gouge into the fault zone.  It may eventually undermine the highway above it.  ADOT will need to deal with it at some point.

Photo point 4:  Oak Creek Fault. 

Heavy rains also enlarged this scar into the crushed sandstone. 

Photo point 5:  A slump block fracture.

Two more slump block fractures.

Photo point 6:  Geology board at the Oak Creek Canyon view point.

Photo point 6:  Oak Creek Canyon from the viewpoint.

1.  The main fault line.

2.  The secondary fault branch.

3.  Pine Flat Campground.

Below the switchbacks water flows out of the ground at both faults.  Sterling Springs, the headwaters of Oak Creek, gushes out of the main fault. Harding Spring, the artisan well next to the highway, flows out of the secondary fault.  There are also several ambiguous springs located in the creek bed itself.

At Pine Flat Campground the two faults converge.  Oak Creek and Highway 89A meander over the fault as they travel down the canyon.  At Slide Rock Lodge the fault splits again, one branch staying with the creek and the other veering for Wilson Mountain.

A secondary branch slices the side off Wilson Mountain and splits a volcano in half creating the suspended block known as First Bench.  There are hiking trails to First Bench and the top of Wilson Mountain from Ensinoso Picnic Grounds and Midgley Bridge.

The core of the volcano has been laid open by the fault.

   

1.  The volcano erupted through the Kaibab Limestone Formation after it had risen above sea level.  

2.  A dense magma conduit that likely fed the volcano.

3.  Layers of reddish volcanic cinders known as tephra.

4.  Older lava flows that were lifted and tilted by this volcanoes eruption.

Just south of  the Rainbow Trout Farm the main fault exits Oak Creek Canyon altogether and heads up Casner Canyon to Schnebly Hill directly east of Sedona.

The last mile to the top of Schnebly Hill. 

Fault escarpment 

The fault escarpment is a pulverized zone of Coconino Sandstone exactly like what is found on the Switchbacks.  Schenbly Hill Road was dug into the side of it.

The fault is buried under a talus slope and covered

with vegetation across the face of Schnebly Hill. 

It passes through the saddle between Schnebly Hill

and Munds Mountain and into Jack's Canyon beyond. 

Jacks Canyon makes a right turn at the far end 

and leads 3.5 miles to The Village of Oak Creek.

After the Oak Creek Fault crosses into Woods Canyon (Dry Beaver Creek) it is buried under thick lava flows 4 to 16 million years old.  I don't believe it just stopped there because Lee Mountain is still 400 feet higher than the lava flows on the opposite side of Jack's Canyon.  The fault may continue and cross Interstate Highway I-17 south of the Stoneman Lake Exit and into Rarick Canyon or just peter out altogether.  There are no surface indications to what takes place.

Oak Creek Fault is a normal fault, meaning that the opposing sides move vertically.  Because of his it doesn't necessary have to travel in a straight line and can wander along changing planes of weakness.  In comparison, the San Andreas Fault slides horizontally and for hundreds of miles is basically a straight line. 

There are at least five volcanoes that are on or next to the Oak Creek Fault:  the San Francisco Peaks, A1 Mountain, Naval Observatory Hill, Woody Mountain and the Wilson Mountain volcano.  This is because deep rooted faults can provide a conduit for magma to reach the surface.  Oak Creek Fault is continuous into the basement granite rocks of the North American Continent.



This essay is not a prediction of future movement or volcanic activity, only where the fault is located.  Neither the Oak Creek Fault or any of the slump blocks on the Switchbacks have shifted in recorded history nor did they slide during the recent earthquakes.  Conclusions about the Oak Creek Fault are based on my research and observation of the rock  strata.  I believe the data I have presented here to be accurate; however, what I have presented here is solely my opinion.