Monday, November 29, 2021

Don't Miss This Fans of Arizona Geology!

 This from Michael Conway at the Arizona Geological Survey.

 

Photo: Hunter’s Point, south of Window Rock, displaying a beautiful expression of the
East Defiance
 monocline, Laramide fold. The rocks are mostly sandstones of 
Pennsylvanian through Triassic in age.     Photograph by Stephen J.Reynolds


Arizona Geological Society presents

Roadside Geology of Arizona

Stephen J Reynolds and Julia K Johnson  

School of Earth and Space Exploration

Arizona State University

 

Tuesday, 7 Dec. 6:30 p.m. (MST)

ZOOM (https://arizona.zoom.us/j/87908544524)

Passcode: AGS-2021

              ZOOM Venue open at 6:15 p.m.

 

ABSTRACT. Arizona is an amazing showcase of geologic features and processes. The landscapes of the state reveal a fascinating geologic story, and most chapters of this history can be observed by traveling Arizona’snetwork of federal, state, and local highways. With some strategies for observing landscapes and a general understanding of the of and events,a traveler can piece together the main plot lines of the history. We are using this observe-first, stratigraphy-first approach to write a new version of Roadside Geology of Arizona. In this talk, we will employ a regional approach to Arizona as      we explore the geologic scenery of different parts of the state, highlighting the stratigraphy, structural styles, key geologic events, andnotable scenic landmarks.

 

 Presenters

Dr. Steven J. Reynolds was recently named ‘President’s Professor’ at ASU. He has au thored or edited more than 200 geologic  maps, articles, and reports, including the    866-page “Geologic Evolution of Arizona.            Steve is a past president of the Arizona Geological Society.

 

Ms. Julia K. Johnson is a geologist and geoscience-education researcher. Her geologic research focuses on the geologyof Arizona, and her education research involves the use of concept sketches in geoscience learning and teaching. She is a  co-author of one of the Arizona Geological Survey’s most popular contributed maps: “Geologic Map of thePhoenix Mountains, Central Arizona”  (~60,000 views).

Friday, November 26, 2021

End Cretaceous Tsunami Event Recorded in Rocks on the Tora Coast in New Zealand

 

This one from my colleague and good friend Jack Share. Watch this five minute video here to understand how a deep sea rounded conglomerate was formed. And be sure to check out Jack's blog, Written In Stone: Seen Through My Lens.

Monday, November 15, 2021

Salvage Geology in Cataract Canyon

Aerial view of the confluence of the Green (light brown) and the Grand (darker brown)
that formed the Colorado River (left) prior to 1922 . (Image taken May 25, 2015) 

I've run the rapids through Cataract Canyon in Canyonlands National Park and Glen Canyon National Recreation Area a few times and marveled at the exquisite geology exposed there. In fact, I believe that the country surrounding the confluence of the Green and Grand rivers is the quintessential location of the heart of the Colorado Plateau. Names like the Orange Cliffs, the Land of Standing Rocks, and Island in the Sky evoke images of stratified terrain that may be equaled elsewhere nearby but never surpassed. You can see some of my past blog postings of trips through the canyon here, here, and here.  

Image taken May 25, 2015

The ongoing drought in the American Southwest has caused the level of the Powell reservoir behind Glen Canyon Dam to drop 156.5 feet from its full pool elevation of 3,700 ft. (above mean sea level). This has caused the once drowned channel of the Colorado River in Cataract Canyon to slice through over 35 years of sediment within a narrow, confined channel. In the photo above, you can see part of this great sediment pile directly above the boat and in the shadowed bank on the right. The Powell reservoir once inundated  these terraces but the lower level of the reservoir causes the river to slice through them.

The Powell formation. Image taken May 25, 2015

Now, the Returning Rapids Project is documenting the scientific and social significance of this sediment excavation event. You can read an article from the Salt Lake Tribune here about some of the results. 

For the Edward Abbey that resides in many Southwestern souls (and I proudly proclaim my fondest affection for the anticipation of the demise of the unneeded reservoir), this is an exciting moment in time. It is an opportunity for scientists to monitor both the deposition of the Powell beds for the mid-1960s to about 2000, and the erosion of this sediment pile as the level of the reservoir drops. 

In the linked article, the author refers to the sediment body as the Dominy formation, after Bureau of Reclamation Director Floyd Dominy, who essentially spearheaded the drive to construct Glen Canyon Dam in the 1950s. However, all rock units in geology must be named after a geographic location where they are first studied and described (called the type section). Until someone names a feature after Dominy, a better name for unit might be the Powell reservoir formation, or simply the Powell formation (both names in a rock unit are capitalized if the name has been formalized with a scientific description; if it has not yet been described then the suffix name is lower case, signifying that it is an informal name).

Monday, November 08, 2021

My First Grand Canyon Backpack Since Knee Replacement Surgery

Well, it is nice to have this goal finally achieved! 23 months after having two total knee replacements, my wife and I headed back down to the bottom of the Grand Canyon on a six-day backpack. While rehabbing after surgery in December, 2019, a photo of me hiking the Tonto Trail in 2017 was placed on the wall of my hospital room to serve as inspiration to see my recovery through. It worked!

And I owe it all to this lovely lady, who was by my side these whole 23 months and made the necessary arrangements for my volunteer lectures at Phantom Ranch! Thank you Helen from the bottom of my heart (and knees).

To say I was bit uneasy to see if my knees could withstand the steep descent of the Bright Angel Trail doesn't convey fully my concern. 

Within 50 meters, my left knee began its odd pain. But after the Mile-and-a-Half House, I took a break and upon beginning again, the pain was gone for the rest of the trip. It apparently was just warming up.

And then it was like the other hundreds of hikes I have completed here such that the beauty and scale of the Grand Canyon took over! This is Jacob's Ladder through the Redwall Limestone.

This is the view from Plateau Point across to Zoroaster Temple. The weather could not have been better for hiking the entire six days.

I had never before noticed these detailed trilobite appendage traces in the Tapeats Sandstone near Plateau Point. The critter was swimming in shallow water but pushing across the bottom sand.

At Plateau Point proper, these trilobite "landing" scours have always impressed me. Imagine the swimming sea creature coming down to the shallow sea floor and scooping out a place for itself. Note also in the upper left a trace known as Corophioides, paired holes at the top of the bedding planes that transition to concave-upwards scours at their base. These are interpreted as dwelling structures for suspension-feeding organisms such as annelids.

One of the trail guides we met out at the Point told me of a trace fossil he has stashed (people steal these things) so that he can continually show his guests trip after trip. I used this technique myself when I was a trail guide. This is a trace known as Rusophycus, a resting or predation escape structure for a trilobite.

A beautiful sunset was seen from Plateau Point toward Dana Butte. Horn Creek Rapid at relatively low water can be seen (and heard!) from Plateau Point.

The Tapeats Narrows along the lower Bright Angel Trail is one of my favorite places in all of Grand Canyon.

Beautiful Buddha Temple framed by Fremont cottonwoods.

Finally, the bottom of the canyon and the Colorado River was achieved.

This was our home for 4 nights - Bright Angel Campground site 17.

I gave a geology lecture to guests at the Ranch each afternoon at 4 PM. I talked about Grand Canyon rocks and how the canyon was carved.

Rocks and resources for the talk were available.

The lectures were well attended and appreciated by tired hikers and sore mule riders.

An outcrop of boudinage in Bright Angel Campground was nearby.

The most beautiful view I know of is located here along Bright Angel Creek.

Thanks for believing I could do this Helen! Let's do it again soon!

Monday, September 20, 2021

Five Suggestions for Books on the Geology of the American Southwest and Colorado Plateau


I was recently contacted by Shepherd, a web-based company that helps promote the books of authors in certain subjects, who then list five books that the authors recommend to learn more about their subject. I chose the subject - Geology and Landscapes of the American Southwest and Colorado Plateau.

You can access the home page to my featured book and my five recommendations here. The title Shepherd features from my portfolio of books is "Carving Grand Canyon."

And the five books I recommend to those who want to dive into the geology and landscapes of the American Southwest and Colorado Plateau are:

Hiking the Grand Canyon's Geology by Lon Abbott and Teri Cook

Volcanoes of Northern Arizona by Wendell Duffield

Desert Heat, Volcanic Fire by David Kring

Geology of the Canyons of the San Juan River by Donald Baars

Geology of the American Southwest by W. Scott Baldridge

All of these books will bring you along in your discovery of the amazing geology here. Please check out the page at the link above or here.

Sunday, September 12, 2021

The Snake River Through Hell's Canyon - Idaho and Oregon

At the end of August I was invited to go on a private river trip through Hell's Canyon on the Snake River. This trip had become visible on my radar just a couple of years earlier and so I jumped at the opportunity to something completely different than the American Southwest. Enjoy the ride downstream with me!

The trip began right below Hell's Canyon Dam with a height of 310 feet. A much larger dam (710 feet high) had been proposed to inundate much of the scenery seen on this river trip. But a compromise with conservationists included this dam and two others immediately upstream in order to preserve the most scenic sections of the 652,488 acre Hell's Canyon National Recreation Area

A view of the put-in below the dam. It is quite tight bringing a vehicle down from the USFS Visitor Center and the ramp is steep and narrow.

Location on the border between Idaho and Oregon.
Two other large rivers parallel the Snake River, the Imnaha to the west (shown left of the words "Hells Canyon) and the Salmon to the east (far right). Later in this point I will show the confluence of the Salmon with the Snake.
Legend for the map above.



There were five of us in three boats.

There were historical and (some) refurbished cabins along the way.

Scouting one of the Class IV rapids called Wild Sheep Rapids. This was only four miles from the put-in. There were four rapids of this size.

About 67.5 miles of the river is managed under Wild and Scenic designation, with the first 31.5 miles as Wild and the remaining 36 miles as Scenic. Still, upriver jet boats were grandfathered in as part of the 1975 compromise bill to designate. We saw many.

Native pictographs on river right.

There were forests high up on the cliffs and Ponderosa pines were common along the river in the first half of the trip. Grasslands dominated much of the run.

Waterspout Rapid. This was the last of the Class IV rapids we encountered. Note the hole on the far left known as the Green Room. At much higher water levels (we had relatively low water our whole trip of between 8,000 and 16,000 cfs) this is major hazard to boaters as it recirculates strongly. All guidebooks mention how it is necessary to miss the Green Room. As a passenger on my raft, I wax treated to a perfect run through the Green Room!

I wondered if the grassy environment we saw throughout the canyon might be evidence for prehistory fire regimes altering the ecosystem. It certainly seemed that could be the case.

First nights camp on Johnson Bar and our only camp on the Idaho side.

The fluctuating releases from Hell's Canyon Dam meant that our boats were often stranded in the morning. All of this was reminiscent of earlier days in the Grand Canyon before releases at Glen Canyon Dam were changed to preclude such wide swings in the river level.
 
Another old cabin along the river in Idaho, this one called Sheep Creek Cabin. The Forest Service places volunteers at these cabins to manage the property and boaters can rent them during the river trip. A fig tree here was full of fruit that the caretaker said was visited by a black bear the previous evening. A large branch was lying on the ground from the visit, denuded of fresh figs. I really enjoyed eating them too.

As we moved downstream Hell's Canyon began to widen out a bit. Then a tall terrace of debris began to appear on either side of the river. In this view of river left, it rises from the riparian zone near the raft, up the grass covered slope about 150 feet.

Here is a more obvious view on river right a bit further downstream. This terrace formed during the Bonneville flood, when Pleistocene Lake Bonneville spilled over its lowest rim and in a matter of a few days was lowered 300 feet. All of the runoff came through Hell's Canyon!

Map of Lake Bonneville and the path of the Bonneville Flood during the Pleistocene, some 14,500 years ago. Lake Bonneville began to overtop its rim in Red Rock Pass in southern Idaho and spilled northward toward present-day Pocatello Idaho where it entered the Snake River. Map taken from Fallschirmj├Ąger - based on a map by Laura DeGrey, Myles Miller and Paul Link of Idaho State University, Dept. of Geosciences. https://commons.wikimedia.org/w/index.php?curid=25056130.

The Kirkwood Cabin area and its caretakers get a visit by our group.

The Columbia River Basalts began to appear just before we neared Pittsburgh Landing. This area marks the end of the Wild portion of the Snake River. The Columbia River Basalt Group records an epic effusion of lava flows covering 81,000 square miles in the American Northwest. Eruptions were mostly between 17 and 14 Ma but smaller eruptions continued until about 6 Ma. These layered lavas sat on top of the basement rocks we encountered along the rivers edge.

Near Pittsburgh Landing, we saw a Cascade Range ash bed in the riverside alluvium. I am unaware of the provenance of this light-colored ash bed but our river guidebooks mentioned that ash from Mt. Mazama (Crater Lake) was present in the area.

Below Pittsburgh Landing the canyon became narrow once again as the Seven Devils Group was exposed. See an early USGS Professional Paper about this package of rocks here. These volcanic, volcaniclastic and marine rocks are Late Permian to Triassic in age and have been interpreted as being formed in the Panthalassic Ocean (early eastern Pacific Ocean), perhaps to within 18┬║ of the equator (north or south). These rocks were then transported tectonically to the north, ultimately colliding with the ancient western edge of North America. Some geologists ascribe these rocks as being part of the Wrangellia Superterrane.

Permian-age pillow basalts of the Seven Devils Group along the Snake River in Hell's Canyon.

Another view. Incredible to think of the geologic history these rocks contain!

In the distance looking downstream, note how far down the Columbia River basalts are. I wondered if maybe they have been erupted onto paleotopography? Another likely scenario is that the rocks were faulted low.

Some of the camps (not reserved in any instance) had picnic tables. This is Bob's Camp.

Looking upstream.

Rock bar.

Columnar basalt next to the river. The vertical joints form perpendicular to the cooling surface.

This is the confluence with the Salmon River, seen coming in from the east (left). The Snake River is shown on the right.

Panorama of our last camp at river mile 175.6 and within the state of Washington.

A large fire had scared the Idaho side of the river all the way from the confluence with the Salmon River and the take-out, some 17 miles of river.

At the take-out at Hellar Bar, the Columbia River basalt dominates the landscape. What a trip! Thank you to Mike, Tiffin, Sandy, and Gail for such a great journey down through Hell's Canyon.