Wednesday, April 08, 2020

Facebook Live Session on Grand Canyon Geology!

Do you like the Grand Canyon? Do you have an interest in geology and Earth history? Or perhaps you are just looking for something to do during a global pandemic? If so, you may want to tune in to a Facebook Live session I will be presenting on Thursday, April 9.


The session will be conducted at 9 AM Arizona time (which is also 9 AM Pacific Daylight Time); 10 AM Mountain time; 11 AM Central time; and 12 Noon Eastern Time. (Coincidentally, it gives me great joy to list the Mountain and Pacific times first!). 

You can learn more about this event here: https://www.facebook.com/geologylearn/.


Please note: If you cannot attend the live session, it will be recorded and available for viewing at a later time!

The session will be hosted by the blog site, Learning Geology created and administered by Muhammed Qasim Mahmood, an Earth scientist living in  Lahore, Punjab Province, Pakistan. Learning Geology is a science website and a community of Earth scientists [that] share geology lessons and host Live Virtual Field Tours.

As you begin to tune into the session, you can invite others to attend and please do so! I will begin by giving a short introduction to Grand Canyon's rocks and its development. Viewers will then be able to submit written questions right on the site. This live session will last no more than 45 minutes to one hour in length. And if I am unable to answer your questions while Live, I can answer them in written form right on the site. The questions and answers will also be viewable at a later time.

The times again are:

9 AM - Arizona and Pacific Daylight Time
10 AM - Mountain Daylight Time
11 AM - Central Daylight Time
12 noon - Eastern Daylight Time
6 PM - Central European Daylight Time
9 PM - Pakistan Standard Time
2 AM - Australia Eastern Standard Time
4 AM - New Zealand Standard Time
6 AM - Hawaii Standard Time

Join us for what is certainly going to be a fascinating discussion of the geology of Earth's most magnificent gorge!

Although Grand Canyon National Park is closed during the pandemic, we will be discussing its fascinating geology on Facebook Live! Thursday, April 9 at 9 AM Arizona and Pacific time. 

Tuesday, March 24, 2020

The Tinajas Altas Mountains and Cabeza Prieta National Wildlife Refuge

“I have always loved the desert. One sits down on a desert sand dune, sees nothing, hears nothing. Yet through the silence something throbs and gleams…”   

Antoine de Saint-Exupéry, French writer, poet, aristocrat, journalist, and pioneering aviator

And so it goes. Where there is nothing, often there is everything. I think that is why I love the desert. Although I am not strictly a religious person, I revel in the fact that many of humanity's greatest and largest religions originated in desert environments. One feels close to God, perhaps, because one can see farther in the desert. I wonder if many people ever think of the environment where their belief system developed? Does it matter? Why do people in North and South America hold on to traditions originating from the Middle East? I think about these things while traveling along the smooth, hard roads in the desert. I also think about geology - time travel at its finest. Brace yourself - there is a wonderful geologic story about this place below!

I've had a long-time desire to see and visit the historic Tinajas Altas (meaning High Waterholes in Spanish), located in extreme southwest Arizona, along a historic route known as El Camino del Diablo (The Devil's Highway). People have been coming to these hidden pools along the Camino as long as there have been people here - nearly 13,000 years! And before the self-isolation of the current times began, myself and some friends planned a nice four day trip to this hidden oasis.

The Tinajas Altas Mountains are located within a one million acre+ military reservation known as the Barry M. Goldwater Range. Every person on our trip was required to fill out an online permit to enter the range for recreational purposes. It is located between Tucson and Yuma along the Mexican border in southwest Arizona and was created immediately after the Pearl Harbor bombings to train fighter pilots for that war effort. We made a base-camp for three nights in one place and explored a few areas from there. The Cabeza Prieta National Wildlife refuge abuts the bombing range on the east.

Signs like this were evident everywhere to discourage off-road exploration. This trip is not for the faint of heart as jets come seemingly out of nowhere, buzzing the desert floor on training missions.

DAY 1 - El Camino del Diablo Este

Sign announcing the northern boundary of the range.

My only surprise is that there are not more bullet holes in this sign.

After about 24 miles of dirt travel, a sign announces the location of the once hard-to-find waterholes.

A view of our base-camp looking toward the east on our first day. In the background are the Cabeza Prieta Mountains. Love those cirrus clouds framing them!

DAY 2 - Visiting the Tinajas Altas

On our first morning we went 1/2 mile south to the water holes. This large granite boulder contain an opening that could easily fit five to six individuals during a hot summer day or spring rain storm. Something like this would obviously serve prehistoric populations well! The rocks belong to the Gunnery Range batholith, a moderate-size intrusion from the Late Cretaceous period (batholiths by definition are larger than 100  square miles.

The Tinajas Altas Mountains belong to the Basin and Range Province, where blocks of the Earth's crust pulled apart and rotated beginning about 17 to 20 Ma (Mega-annum or millions of years ago). The event created long, uplifted ranges, separated by parallel and adjacent down-dropped basins. This occurred from southern Oregon into northern Mexico and out east to west Texas. Both the ranges and the basins appear linear on the landscape (see the trend of the Tinajas Altas and Mohawk Mountains on the map at the top).

The Tinajas Altas are composed of granite that was intruded as magma into the crust about 70 Ma. At that time, the Farallon oceanic plate was being subducted beneath the western edge of North America. This crumpled the crust well enough, but it also caused an influx of volcanism, as melting commenced at depth on the down-going oceanic plate. The melting formed granite, which you see in the photo above. In the last 70 million years, the overlying rocks that contained the magma have eroded way.

This is what southwest North America looked like about 70 Ma. (Note the modern state and county lines overlain on this ancient geography for reference from the book, "Ancient Landscapes of the Colorado Plateau", by Ron Blakey and Wayne Ranney). The red dot denotes the location of the Tinajas Altas Mountains. This is where the Gunnery Range Batholith was intruded into a large mountain range known to geologists as the Mogollon Highlands. The Pacific Ocean is located in the extreme southwest corner of the map. There were short, steep rivers running southwest out of the Mogollon Highlands to the Pacific. And very long, low-gradient rivers running northwest all the way into the Mississippi River system at this time. Think about that!

To further explain, I have overlain a map of the Amazon drainage in modern-day South America over that of modern-day North America. South America is a perfect modern analog for how the landscape and drainage pattern looked in the Late Cretaceous period in North America. In South America above, the Andes Mountains are the source of the Amazon with flow across the entire continent to the Atlantic. In Cretaceous North America, rivers rose in the Mogollon Highlands and flowed across the future Colorado Plateau and Rocky Mountains region into the Gulf of Mexico. What a joy it was to visit the roots of the ancient Mogollon Highlands in the Tinajas Altas Mountains!

Then, after the passage of 70,987,000 years, people arrived leaving their mark on the landscape near the thirst-quenching pools of fresh water. These are grinding pits called metates where people processed wild seeds near the tinajas.

The first and bottom-most of nine pools.

A few others in our group scrambled up to see pools two and three. I was unable to do that recovering from knee surgery.

Who knew Chuckwalla's love the taste of brittlebush flowers!

DAY 3 -To the Cabeza Prieta and Christmas Pass


Not your usual sign when undertaking recreational pursuits.

God only knows what this mannequin is supposed to represent or do. There was a live flare in its holster so perhaps if someone is in dire trouble they would approach anything that looked human and use the flare.

Evidence that walkers have been through here.

We saw many of these beautiful Desert lily's blooming (Hesperocallis undulata). They are also called Ajo lily's because of the bulbs garlicky flavor.

This is the feature that gives the Cabeza Prieta Mountains their name, Cabeza Prieta Peak (elevation 2485 ft.). Cabeza Prieta means Black of Dark Head in Spanish. A remnant black lava flow caps the light-colored Gunnery Range Batholith. When the Basin and Range Province was formed, andesitic magma welled up through the weakest parts of the extending crust to erupt these lava flows. Radiometric dates have been obtained from these lavas. The flow on the peak is dated on Potassium/Argon, whole rock at 16.12 Ma and a dike is dated on hornblende minerals at 17.81 Ma. These dates are clearly within the timeframe of Basin and Range extension.

Finally, we arrived at Tule Well, a well-known source of water that was hand dug in the 1850s. The giant dump truck is coming back for another load of sand to be used in the construction of the new border wall.

The dirt track was quite busy with construction traffic. Out of the 11 folks in our group, 10 of them thought the construction of a new wall was a waste of money.

Scorpion weed (Phacelia crenulata) is part of the Waterleaf family of plants with over 100 different species in Arizona.

Thanks to reader Barbara Yarbrough who correctly identified this as Miniature Woollystar (Eriastrum diffusum).


A Desert sunflower (Geraea caneacens) grows in front of the door of the adobe cabin built in 1989 at Tule Well.

A field of Desert Sunflowers in bloom. I would say that we hit the peak of flowering in this low desert spring bloom.

I couldn't tell if this was Teddy Bear cholla (Cylindropuntia bigelovii) or one of the other Cylindropuntia's. But I'm going with Teddy Bear cholla.

DAY 4 - El Camino del Diablo Oeste


Originally, we had hoped to enter the area from the east through Organ Pipe Cactus National Monument and work our way west. However, the intense rains that this area experienced just before our arrival made that a difficult route to travel. So we stuck to to the western side of the Goldwater Range where the granite soils were drier and more manageable. Therefore, we exited the area on the western branch of El Camino del Diablo. This route follows the western base of the Tinajas Altas Mountains. The flame-tipped ocotillo (Fouquieria splendens) was in full bloom!

Close-up of the flame tips.

Beautiful desert drive!

Saying good-bye for now to the Tinajas Altas Mountains. Rich geology, colorful plants, clear skies, and wonderful friends. We did however come back to a much different world.

Friday, March 13, 2020

Meet the Aiken's, Who Lived in the Bottom of the Grand Canyon for 33 Years

Bruce Aiken's "Splitrock" painting. Splitrock is located between Cottonwood Camp and the Powerhouse on the North Kaibab Trail in Grand Canyon.
I was a National Park backcountry ranger between 1975 and 1978. In the Bicentennial summer of 1976, I was the ranger at Cottonwood Camp, located halfway between the North Rim and the Colorado River. One and a half miles north of the ranger station was the Powerhouse, a Park Service residence where the North Rim pump station operators lived. In 1976, the Aiken family lived here, Bruce and Mary and their two girls Mercy (age 4) and Shirley (age 2). We became good friend as the only "residents" living along the 14 mile long North Kaibab Trail.

Read about the Aiken's and their amazing life journey on this ultra-marathon web site (ironic since I have been an outspoken opponent of competitive running on the trails in Grand Canyon). You can read Anne' wonderful story here. And within it, you'll read about a young, 22-year-old backcountry ranger who came to the aid of young Shirley one hot summer night!

Wednesday, March 11, 2020

Flashback - The World's Driest Desert, The Atacama in Northern Chile - January, 2008

After flying half way up the length of the South American continent, we landed in Calama in northern Chile. Chile is the Earth's longest country and if it were transposed latitutinally to the north, it would stretch from Ketchikan, Alaska to Acupulco, Mexico! It goes from glaciated mountains in Patagonia, to the temperate wine growing region near Santiago, to the Atacama Desert, which is the Earth's driest. Some places here do not receive rain for decades!

The Andes Mountains as we approach Calama in our jet.

Look at this - 8,000 feet above sea level and not a hint of vegetation anywhere. 8,000 feet and nothing but gravel!


A fantastic angular unconformity. The rocks below were once flat-lying sediments. They were tilted to vertical during the uplift of the Andes. Then they were eroded flat before the upper layers buried them. Scenes like this inspired original geologic thinking in humans.

2020 Update - The lower brown and upturned beds belong to the San Pedro Formation, shale, sandstone, conglomerate, gypsum and salt deposited in a playa environment. It is Late Oligocene to Miocene in age. It is overlain by the Vilama Formation of likely Pliocene age. It is composed of silt, sand, and gravel deposited by streams out of the Andes Mountains.

Submitted by fellow geologist Paul "Geoman" in Texas

Atacama ghosts posing as pillars of salt. This is part of the Salt Range.

I visited the world's highest geyser basin on Tuesday. This is at 13,000 feet and the geysers were spectacular!

This is a boiling mud pot, reminiscent of Yellowstone. There are at least 50 to 60 geysers constantly erupting in this field.

Awesome thermal structures in El Taito geyser field. It started out cloudy but then the sun made its way through the mist.

The high Andes in the background of the geyser field rise to over 19,000 feet. The snow is unexpected however considering it is summer down here.

Just another awesome Andean volcano with summer time snow. This one is called Sarécabur and at 19,500 feet, it forms the international bounday with Bolivia. The Andes and the Atacama have received a lot precipitation recently.

Vicuña's are related to llama's and I saw dozens of them running across the altiplano as we drove home from the geyser field.

Sunday, March 01, 2020

Flashback to November 1, 2015 - Ayers Rock and The Olga's Australia

After a few days in Alice Springs, it was time to head southwest to the main attraction of this region, Ayer's Rock, also known by its Aboriginal name Uluru.



The distances are long in the outback and I took this picture at the highway junction in Erldunda. Distances shown are in kilometers and this is half way to the rock from Alice.


Connor Butte as seen from a scenic overlook along the way. It is composed of Paleozoic sedimentary rocks.


Lake Amadeus is one of the many dry lakes located in central Australia


Our first view of Ayers Rock from the Yulara Resort. This would be the sunniest view of it during our stay, as wet and thundery weather moved in.


Dramatic skies frame the eastern side of the rock


The grass is called spinifix and it is very tough and drought resistant species


The rock is composed of a coarse sandstone called the Mutitjulu Arkose (arkose is a term used for sandstones that have a lot of feldspar mineral included - a feature that distinguishes arkose as having been deposited relatively close to the source area).


Eucalyptus trees frame the rock. Note the desert tapestry streaming down from the top, formed where water allows bacteria and lichens to grow.


On to the waterhole


Rock art in one of the overhangs near the waterhole. Aboriginal culture extends back more than 40,000 years in Australia and recent DNA testing shows that the line is most closely related to people now living in Sri Lanka.


Graceful canyon cut into the Mutitjulu Arkose


The rock is part of an upturned package of sandstone deposited about 550 Ma. That means it was laid down within about 9 million years of the Precambrian/Cambrian boundary. No land plants or animals existed when this sandstone was laid down.


This is the northwest side of the rock and we walked to the amphitheater seen where the long desert tapestry come down the cleft.


A closer view with gum trees in the foreground


This is a special spot


Looking up through the trees at the edge of the monolith


Rock and trees


Around the base of the rock are numerous cavities called tafoni. They are formed when water in the soil seeps into the rock, helping to dissolve the cement around the sand grains. This weakens the sandstone here and a cavity is formed, The dissolved cement is then transported by the same water to nearby where it precipitates causing the nearby sandstone to become extra hardened, That is how the roof pendants are formed.


Champagne and h'ors douves at the Ayers Rock


Group photo at sunset


At 6:01 the sun set but it was nowhere to be seen


Sunrise at Ayers Rock. Many people turned out even though it was raining at 5 AM.

This was about as good a shot as I could get. It was very dark and cloudy.


After breakfast we went west to see the Olga Mountains (or Kata Tjuta in the local Aborigine language). These rocks are the same age as those in Ayers Rock but as you will see are composed of something different.


Walking up into  a gorge cut between one of the 18 domes of rock


Yep. This is a very coarse-grained conglomerate with clasts of crystalline gneiss and granite. Look at the size of those clasts! The interpretation is that this and the arkose at Ayers Rock were derived from the Petermann Mountains just a few miles west of here in latest Proterozoic time. At the Olga's, the streams delivered bouldery sediment whilst at Ayers Rock it was coarse sand. Two co-eval alluvial deposits from an ancient mountain range.



Tafoni and desert tapestries in the walls of the gorge


Three of the domes at the Olga's


The wind blown sand here is extremely red - more red than that seen in Arizona, which is more orange. In spite of the cloudy weather, this was a great visit and I was more impressed with "the rock" than I thought I would be. Still it is a small feature compared to all that we have in the American Southwest but Australia's Red Center is a unique and intriguing place.


A first view of Sydney, Australia. Watch for my next posting from Sydney soon.