Friday, August 21, 2020

THE DARTON DOME ENIGMA


Several years ago I was working on a story about Strawberry Crater.  I had already explored the dead volcano and had taken a number of photos but I had not captured one that showed the entire cinder cone from a distance.  The problem had been the tall Ponderosa Pine trees that obstructed views around it.  

Later on at home I used Google Earth to locate a minor, unnamed volcano off of Forest Service Road 546 that I thought might offer a clear view of the cinder cone.  In February of 2015 I drove from Flagstaff and found the small volcano and hiked up to its rim.  I was not disappointed, from the top I had a clear view of Strawberry Crater two miles to the north-east.


Strawberry Crater


I took the photos I wanted then stopped to look around from my vantage point above the trees.  O'Leary Peak was two miles to the south-west with Darton Dome next to it.  I was slightly familiar with O'Leary, I had climbed it and the fire-tower at its top nearly 40 years ago.  I didn't remember anything unusual about it at that time but now, from this direction, it looked very different.  O'Leary Peak wasn't just next to Darton Dome but looked like it was inside of it.  


The Darton Dome / O'Leary sandwich.


I had seen O'Leary Peak many times over the decades from Sunset Crater Volcano National Monument to the south and east but never from the north.  From here it appeared as if O' Leary had bisected Darton Dome and shoved the two halves apart as it extruded up between the dome.  

Technically Darton Dome only refers to the hill on the left, O'Leary Peak is the tallest one in the middle and an unnamed dome is on the right I'll call Dome B.  When viewing O'Leary from the south or east Dome B is hidden from view.  



Because of the cliff faces on both domes it appears they were once joined together. 


Below is another photo of the cliff face on Dome B from a different angle.  Some might argue it is the lateral edge of a thick dacite lava flow but I don't believe it would be that tall, vertical and void of vegetation.  For the cliffs to have formed from stream erosion or glacial activity is unlikely.  The O'Leary Mountain is just not big enough to provide the accumulation zone necessary for enough ice or water to erode those cliffs.  It looks more like a sheer fracture to me.


Dome B cliff face


If I was a younger man and not handicapped I would climb up and get rock samples from each of the cliff faces and the flank of O'Leary Peak.  Determining the rock chemistry and age of each flow might explain what happened here.  O'Leary has been dated at 200,000 years old but I don't know about Darton Dome and Dome B.  If they have the same chemistry and age that would suggest they were once joined.  If O'Leary is younger than the domes then it erupted after the two domes were in place. 

There in one more factor to add to this mystery that I only recently learned.  Doney Fault is visible on the surface eleven miles to the northeast in the Wupatki National Monument.  The north end of the fault heads away into the Little Colorado River Valley and the south end disappears under volcanoes and lava flows.  If it continues on the same track under the lava flows it heads directly under Strawberry Crater and then O'Leary Peak.  


Google Earth Image


Google Earth Image


That fault could have been the conduit for the Darton Dome eruption.  After the dome cooled then motion on the fault could have fractured it and provided the conduit for O'Leary magma to reach the surface and leverage its way through.




Saturday, August 1, 2020

FAULTS OF THE SAN FRANCISCO VOLCANIC FIELD



The San Francisco Volcanic Field is an area of volcanism that stretches from the edge of the Colorado Plateau about 10 miles west of Williams, Arizona for 60 miles to the east of Flagstaff.  It is generally 30 miles wide and approximately 1,800 square miles. Within it lie over 600 volcanic vents, countless lava flows and the San Francisco Peaks, the highest point in the state at 12,633 feet and a stratovolcano.

Faults are common in areas of volcanism for two reasons.  Preexisting faults can provide conduits for magma to migrate through the lithosphere to the surface. Also faults can be caused by a magma chamber rising up from the asthenosphere that forces the crust above it to bulge up and crack.  Since magma chambers can inflate and deflate like a balloon the faults above can open and close and move up or down.

There are six major faults that intersect with the San Francisco Volcanic Field.  North of Flagstaff are the Mesa Butte fault, the SP Graben and the Doney Mountain Fault.  South of Flagstaff are the Lake Mary Fault Zone and the Oak Creek Fault.  To the west is the Bill Williams Fault.  No doubt there are other faults but these are the most visible either on the ground or from space.  Three faults are visible in the Google Earth satellite image below of an area north of Flagstaff; the Mesa Butte fault, the SP Graben and the Doney Mountain Fault. 


MESA BUTTE & BILL WILLIAMS FAULT

Google Earth image.

The Mesa Butte Fault, despite the contradictory name, is impressive.  It is a wide, deep trench visible from the space shuttle at a Low Earth Orbit of 125 miles.  It defines the eastern edge of the Gray Mountain Mesa, then cuts through the mesa as a trench one-quarter mile wide and 600 feet deep as it heads southwest for 28 miles.  It disappears into the San Francisco Volcanic Field at highway SR 180 between Slate and Red Mountain where it is filled then buried by numerous lava flows.

Eastern face of the Mesa Butte Fault escarpment.

4WD road Indian Route 6150 up the Mesa Butte Fault escarpment.

The Mesa Butte Fault trench looking south.



If you draw a straight line between Mesa Butte Fault and extend it southwest to the Bill Williams Fault it will pass directly under Kendrick and Sitgreaves Mountain near Williams.  Both are significant volcanic domes of high silica lava.   It is suggested by some geologists the Bill Williams Fault is an extension of the Mesa Butte Fault and they are one-and-the-same.

Arizona Geological Survey Map image.  Fault are red lines.

Obviously the Mesa Butte Fault named after the Mesa Butte cinder cone was a conduit for magma to reach the surface.  The Bill Williams Fault is not visible by satellite and is much harder to follow.  It too has been covered by lava flows and hidden under vegetation and a Ponderosa Pine tree forest.  


 SP GRABEN

SP Graben is named for SP (Shit Pot) Crater nearby.  It was thus named in reference to the rim of the cinder cone being absolutely covered by a layer of lava droppings that looked like a filthy toilet.  It is, I've been up there.   

SP Crater inner rim

A graben is a geological term meaning two parallel faults with a down dropped strip of land between them.
A graben forms when the land is stretched apart.
If of significant width and length it may be referred to as a rift valley. 

Google Earth image.

SP Crater is a world famous cinder cone in the geological community.  It's near symmetrical shape and well defined features make it the classical definition of a cinder volcano.  The distinctive lava flow and graben made it a choice location for training the Apollo astronauts in the 1960's for the moon landings.

The graben does not appear to be a branch of or connected to the Mesa Butte Fault.  Overall the graben points directly at the San Francisco Peaks.  It is about 8 miles long, 800 feet wide and 100 feet deep before its southern end is buried by the lava flows of the San Francisco Volcanic Field.

SP Crater is not on the graben but 3/4 mile to the east of it, however its lava flow pours into it at two locations.  This suggests to me an intruding magma chamber expanded the earth and the graben formed before SP Crater erupted. 

Two lobes of the SP lava flow drain into the graben.

Oblique view of the lava lobes and graben.

East escarpment wall of the graben.

DONEY MOUNTAIN FAULT

Doney Mountain Fault is north of Flagstaff partly inside the boundaries of the Wupatki National Monument.  It is not remarkable looking but it may have had a big affect on the San Francisco Volcanic Field.
Google Earth image.
It is named for Doney Mountain, a series of small cinder cones formed by a fissure eruption at the south end of the visible fault.  At that point is where the fault disappears under the lava flows and volcanoes of the San Francisco Volcanic Field.
Google Earth Image

Arizona Geological Survey internet image.

Doney Fault escarpment north of the cinder cones.

Limestone escarpment face.

Looking north at the Doney Mountain cinder cones.
Photo copied from the internet.

There is no reason to believe the fault just ends at Doney Mountain cinder cones, it must continue on to the southwest under the lava flows.  Its directional trend takes it close to or under Strawberry Crater,  O'Leary Peak and towards the Dry Lake Hills or Mount Elden.


Strawberry Crater


O'Leary Peak

Mt. Elden (far left) & San Francisco Peaks (center).

Moving south of Flagstaff the Oak Creek Fault and the Lake Mary Fault Zone are outside of the San Francisco Volcanic Field.  However, the north end of both of these faults migrate into the field and under the San Francisco/Mt. Elden volcanic complex once they cross the I-40 Interstate Highway.   

The faults are difficult to see from above because of the dense forest canopy so I drew them in on the Google Earth image below.

South of Flagstaff
Google Earth image

Arizona Geological Survey Map

LAKE MARY FAULT ZONE

The Lake Mary Fault is not one continuous fracture but a series of shorter segments orientated in the same direction.  It is comprised of the Lake Mary Fault, the Ashurst Run Fault and the Mormon Lake Fault which is why it is referred to as a fault zone.  One southern segment runs just east of Mormon Lake and the viewpoint overlooking the lake sits on top of the escarpment.  Other segments define the edge of Ashurst Lake, Anderson Mesa and Lake Mary.

Looking south along the Mormon Lake Fault escarpment.

A second fault runs parallel on the opposite side of Lake Mary which means Lake Mary lies in a graben.  The graben and segmentation of the fault suggests to me stretching of the earth and possible inflation by magma.

Lake Mary graben.

This fault zone has a vertical displacement of up to 300 feet and is about 27 miles long from East Flagstaff to past Mormon Lake where it disappears under lava flows.  It is considered to pose the most likely earthquake threat to Flagstaff and has been active off and on since 1892.    

OAK CREEK FAULT

The Oak Creek Fault is a different beast entirely.  It is one continuous fault with a few secondary branches.  It runs from the San Francisco Peaks for 36 miles south to just past the Village of Oak Creek in the Verde Valley.  It is a normal fault with a vertical displacement of 1,000 feet between the east and west elevations.  It is not known to have slipped in human history but there were noticeable tremors at depth on it in 2014 and 2015.    

Oak Creek Canyon follows the fault.

Diagram at the Oak Creek Canyon overlook.

Wilson Mountain Volcano is cut in half by the fault.

The Oak Creek Fault is old and deep.  It predates the San Francisco Volcanic Field by more than 1.5 billion years.  It has certainly served as a conduit for magma rising from the earth's asthenosphere.  There are at least 5 volcanoes along its path from south to north;  Wilson Mountain, Woody Mountain, Naval Observatory, A1 Mountain and the San Francisco Peaks.

It is obvious that volcanoes are associated with all of the major faults in the San Francisco Volcanic Field which brings me to my purpose in pointing out these faults.  Recently I was browsing the internet looking at geologic photos then I came across this one of quartz veins in a bedrock.  It is an area probably just a few square feet.



The moment I saw it I thought of the San Francisco Volcanic Field and its crisscrossing faults.  I started wondering what would the San Francisco Volcanic Field look like millions of years in the future if were eroded into a flat plane?  I think it would look similar to this except scaled up to many square miles with thick, black basalt dikes through red sedimentary rocks.

That exact scenario has happened at the Shiprock volcano just 200 miles away in New Mexico.  Shiprock is the last remaining remnant of a volcano that erupted 27 million years ago.  Since then the surface volcano has completely eroded away as well as 3,000 feet of sedimentary rock surrounding the monolith.  Radiating out it are three faults called dikes that were the conduits that supplied basaltic magma to the volcano.

Shiprock photo from the internet.

Google Earth image.  Three dikes.  

Dike # 1 photo from the internet.
If this were to occur at the San Francisco Volcanic Field there would be six monoliths stabbing at the sky.  They would be the remnants of Bill Williams Mountain, Sitgraves Mountain, Kendrick Peak, Slate Mountain, O'Leary Peak and the San Francisco Peaks, the crown jewel of them all.  There would be a maze of  long black veins running between them through fractured sedimentary bedrock.  I think that would be quite a sight and look very much like this photo of veins in a rock.


Thursday, October 31, 2019

ASHFORK / BAINBRIDGE STEEL DAM


The Ash Fork / Bainbridge Steel Dam constructed in 1989 was the first of three large steel dams built in the world. It was constructed in 1898 by the Atchison, Topeka and Santa Fe Railway to supply water for railway operations near Ash Fork, Arizona. The Redridge Steel Dam was built in 1901 in the Upper Peninsula of Michigan and is still in use today. The third one in Montana failed in 1908 after just one year of use.



The dam is 46 feet high and 184 feet long and creates a reservoir with a capacity of 36 million gallons. The dam has no spillway since it was designed with an apron along the downstream edge of the crest to allow overflow water to fall clear of the dam.  It consists of 24 curved 3/8 inch steel plates that give the dam a scalloped look. The steel plates alternate between loose and ridged panels to compensate for temperature expansion and contraction. A pipe ran from the bottom of the dam for three miles down the canyon to the Santa Fe station in Ash Fork. 



The Ash Fork / Bainbridge Steel Dam was listed on the National Register of Historic Places on 1976.
It is open for recreational use but the access road to it is not maintained and it requires a high clearance four wheel drive vehicle to reach it, or you can just walk.

The dam lies about 3 miles (4.8 km) to the east of Ash Fork, in Johnson Canyon, and about 15 miles (24 km) west of Williams, Arizona. Take the County Line Road Exit (148) off of I-40 about 1.5 miles east of Ash Fork. Turn north and cross the cattle guard. Immediately past it is a dirt road to the right which is the utility line maintenance road 1601.

Maintenance Road  1601

Follow the maintenance road for 1.4 miles to a very rough road 9731A.  Trees block the view and the dam cannot be seen from this location.  It is one-quarter mile down this road to the Steel Dam.





Tuesday, September 24, 2019

CLIMATE ACTIVIST GRETA THUNBERG


Climate activist Greta Thunberg spoke at the United Nations Climate Action Summit on Monday, September 13th, where she scolded world leaders for failing to address climate change. The 16-year-old has become one of the leading voices for a generation confronting the consequences of a warmer planet.

"People are suffering. People are dying and dying ecosystems are collapsing. We are in the beginning of a mass extinction, and all you can talk about is the money and fairy tales of eternal economic growth," she said Monday, as she fought back tears. "How dare you! For more than 30 years the science has been crystal clear. How dare you continue to look away and come here saying that you're doing enough when the politics and solutions needed are still nowhere in sight."

Greta was selected as Time Magazines Person of the Year for 2019.  Cool!



Friday, September 20, 2019

EARTHFORMS: INTIMATE PORTRAITS OF OUR PLANET


A photography book has recently been released that is worth checking out. Earthforms: Intimate Portraits of Our Planet by Joel Simpson is a photo journey of earth’s geology through time. Inside the front cover is a geologic scale from 4.5 billion years ago to recent time with page numbers where a photo of that geologic exposure can be found in the book. What a great idea.

 



Many of the photos are spectacular and vary from macro-landscapes to closeups which I particularly like. They are taken from locations in the United States, Europe, Asia and Africa and represent a life time of work.  In the back of the book is a section that describes the geology of each photo in the book.

The only disappointment I had in the book was no photo from the Hadeon time period over 4 billion years ago.  It seemed only natural the book should have a photo of the oldest known rocks on earth.  I can understand why not though since they are found in Northwestern Canada and Western Australia.  Both locations are extremely remote and expensive to get to. 

I have added this book to my library.  The book and e-book are available on amazon.com
Link to Earthforms Intimate Portraits of Our Planet





Monday, May 27, 2019

CLIMATE CHANGE and the MILANKOVITCH CYCLES


Some politicians and people outright deny the global climate is changing or that humans could possibly influence the climate.  They further argue that whatever changes are taking place are due to natural planetary cycles although they never explain what those are.  Well, here is the explanation.

Climate change is a long term event that occurs in three predictable cycles as the earth orbits around the sun: Tilt (41k years), precession (19k to 24k years), and eccentricity (100k to 413k years).  They are known as the Milankovitch Cycles after the Serbian astronomer and mathematician who first calculated their magnitude in the 1920's.  The cycles change the climate by altering the amount of solar radiation that reaches the earth.


The tilt of the earth accounts for the changing seasons: winter, spring, summer and fall. The reason is the axis of the earth is at a different angle than the axis of the sun. Consequently, as the earth orbits around the sun the North Pole is inclined away from the sun in the winter and toward the sun in the summer. The South Pole is just the opposite.

The four seasons.

However, the tilt is not fixed and it cycles between 21.5 to 24.5 degrees over a span of 41,000 years. When the tilt is greatest, at 24.5 degrees, whichever pole is facing the sun will be warmer than usual in the summer and the opposite pole will be colder at the same time. This fluctuation causes the polar ice caps to expand and shrink accordingly.

The second cycle is precession which takes 21,000 years. It is a wobble to the tilt of the earth like the motion of the gyroscope below. The wobble increases the tilt and also effects the temperature of the earth and consequently the size of the polar ice caps. 

Precession

The last cycle is eccentricity which is an oscillation in the shape of the orbit of the earth around the sun.  Sometimes the earths orbit is near circular but over a period of 100,000 years the orbit flattens and lengthens.  Since the sun is not in the center of that orbit the planet is further away from the sun more of the time.  In the example given below the position of the sun is greatly exaggerated but it illustrates the idea.

Eccentricity

When the eccentricity is at its greatest the earth is closer to the sun during perihelion (91.4 million miles) and 3.1 million miles further away when at aphelion (94.5 million miles).   

Not to scale.

Individually and collectively the Milankovitch cycles are responsible for fluctuations in the amount of solar radiation that reaches the earth. Of the three cycles eccentricity has the greatest effect on the climate and is the cause of many global warming and cooling events in the past. A study of ocean sediments indicate ice ages have occurred approximately every 100,000 years for the last five million years. Currently the earth is moving toward aphelion and should be cooling off but it is not.

Global Warming is short term and refers to the human caused rise in the global temperature from greenhouses gases, primarily carbon dioxide. When fossil fuels such as coal or oil are burned carbon dioxide is released into the atmosphere. Like a greenhouse it traps heat from solar radiation and also heat from volcanism, forest fires, human industry and cities.  Since the industrial revolution started in 1763 the climate has been warming sporadically since 1880 and continually since 1980.

Global warming is not something contrived in just the last thirty years. In 1886 Savante Arrhenius, a Swedish physicist and chemist, was the first person to calculate human-induced global warming by carbon dioxide. He received the Nobel Price for chemistry in 1903. 

Guy Stewart Callendar, a British steam engineer and amateur climate scientist published a theory in 1938 that linked rising carbon dioxide concentrations in the atmosphere to global temperature. He thought it would be beneficial in delaying the return of the ice age. He was correct.

In the 1950's Callendar's claims provoked a few scientists to look at his work using better instruments and newer technologies that confirmed his conclusions. Their work was financed by the United States Military to determine if it could be useful in a war with Russia.

In 1988 NASA scientist James Hansen presented hard data to Congress that global warming had arrived. Shortly afterward climatologists began informing the general public of the problem and its dangers.

To date 185 member countries of the United Nations have ratified the Paris Climate Agreement, a treaty to address global warming and to reduce emissions of greenhouse gases. Russia, the United States and ten other countries have not agreed to the treaty.

Climate change is a planetary cycle that normally takes place over one-hundred thousand years that would allow time for humans to adapt. Global warming is a symptom of climate change that shouldn't currently be happening that will create unnecessary human suffering and staggering economic cost in just a few hundred years.

An analogy from the National Aeronautical and Space Administration:  If  climate change was the flu,  global warming is its fever.