Thursday, January 22, 2015

Museum of Northern Arizona to Offer Adult Learning Classes on the Colorado Plateau

The Museum of Northern Arizona will offer three different courses this winter/spring related to the natural history of the Colorado Plateau. This is an excellent opportunity for those who live within the Flagstaff area to expand their knowledge of this beautiful landscape. The price of each course is a fantastic deal as well. The courses will be taught by experienced and passionate instructors who have many years of formal training and educational experience on the Plateau. General information about the Museum's Adult Learning Program can be found here.

The courses offered this year are:

An Overview of the Colorado Plateau Geography and Culture - by Alan Petersen, Curator of Fine Art at MNA and Professor of Art, at Coconino Community College. Course dates and sign-up here.

The Natural History of the Colorado Plateau: A View from the San Francisco Peaks - by Dr. Gwen Waring, botanist and author of, "A Natural History of the Intermountain West" Course dates and sign-up here.

Outdoor Drawing - by Alan Petersen, Curator of Fine Art at MNA and Professor of Art, at Coconino Community College. Course dates and sign-up here.

I encourage readers of this blog who live near Flagstaff to take advantage of these offerings. The Museum of Northern Arizona is committed to enriching the lives of those who call this very special place "Home".

Image capture of Member's e-mail notice

Monday, January 12, 2015

Flying A Light Aircraft Over Northern Arizona's Great Landscapes

All photographs on this posting are copyright Wayne Ranney and Ted Grussing


On January 8, I was privileged to fly with Ted Grussing in his light aircraft over the canyons and volcanic fields of northern Arizona. To say that Ted is generous with his time aloft would not convey an idea of the numerous times he has taken anyone up to see the earth from this fantastic perspective. Even those who never ask to go - like me. I never asked Ted to take me me up in his motorized glider plane. He just said to me one day, "I'd like to take you up one day." So in the spirit that I've lived my life in, namely how I've never been able to say "No" to adventure, I said, "Sure"!

On a fantastic "blue-bird" day, I drove down the winding switchbacks through snow-covered Oak Creek Canyon to find Ted pulling his craft out of the mesh fabric hanger it resides in.

Here is a picture of Ted next to his beauty. If you are not aware of Ted or his stunning photographs, you can check them out on his web site here. His work has appeared Sojourns and Arizona Highways, magazines, as well as other well-known journals.

I've always enjoyed flying with anyone no matter what the craft or conveyance. One time on a whim in 1976, I said yes to jumping out of an airplane! It's true I do not always think things out thoroughly. My first inclination is always to say, "YES!" only to find out later that some things are just better left alone. Don't get me wrong - I did not have such thoughts before saying yes to Ted. But when I saw how small the cockpit was, I realized that this was no Cessna flight.

Outfitted with supplemental oxygen, since we were going over 10,000 feet. Heck, I never had supplemental oxygen on Kilimanjaro last summer at 19,000 feet. This was cool.

Taxiing for take-off!

We took-off on Sedona 23 and headed northeast over Oak Creek Canyon. The San Francisco Peaks are in the upper right and the canyon follows the Oak Creek Canyon fault south from their western flank. You can easily see that the west side (left) of the canyon contains colorful, upper Paleozoic strata, more well-known from the Grand Canyon to the north of here. But the east side exposes only basalt lava, suggesting that those rocks were eroded away before the lava flows filled an ancestral valley here. Also, the burn from the Slide Fire can be seen on top of the triangular peninsula on top of the sedimentary rocks. Ted says that he gets much additional lift when gliding over burned areas.

Speaking of burns, there was this a prescribed burn flaring south of Flagstaff. Ted has been outspoken in his opposition to the fires, purposely set to burn slash from forest thinning projects. However, the price to pay is in human health from the particulates and the tainting of otherwise pure mountain air. Ted believes the health risks warrant not burning the piles and suggests they could chip the wood instead. The forest does need thinning but he made me consider if burning is the only option there is to deal with the waste. Perhaps like most things these days, burning simply is the cheapest and easiest thing to do. But, is cheapest and easiest the most civilized thing to do?

There's Flagstaff! In all its clear brilliance on a clear winter day (with the smoke blowing southeast away from town). Note I-40 trending away from the bottom toward New Mexico. Mt. Elden can be seen as the curiously mountain with an "apron" beyond the city.

Here is a close-up of Mt,. Elden with its familiar "apron," actually lobes of dacite lava that formed when very viscous lava erupted from the vent on top. As the lava was extruded it flowed downslope but at an incredibly slow rate due to its viscosity. Tress today have a harder time growing on the solid dacite rock more than the rubble around it and that outlines the distal ends of these lava lobes. All of this occurred around 500,000 years ago in the heart of the Pleistocene epoch (the Ice Age).

Tipping the wings for an unforgettable view of the southwest side of Mt. Elden and its lava lobes.

Flying past the San Francisco Peaks for other volcanic treasures.

Northeast of Flagstaff are the cinder hills, where Apollo astronauts trained for their mission to the moon. Geologists had suspected that the moon would be volcanic and this was a good analog landscape.

There's Sunset Crater, proclaimed a National Monument in 1930 to save it from partial destruction in the filming of a Hollywood movie (it was a screenplay of the Zane Grey novel "Avalanche" and the script called for a western town being destroyed by a mountain landslide).

Note the scenic road that trends through the snow in the bottom left. Ted also pointed out to me the heart-shaped crater or vent on top of the cinder cone. Sunset Crater erupted in the latter part of the 11th century.

Further east we see The Sproul (the elongate cone bottom), Merriam Crater (the highest cone), and North and South Sheba craters. Note how the south-facing slopes are devoid of snow while the north-facing slopes still retain it. These photos were taken about one week after the New Year's Eve snowstorm in northern Arizona.

To the northeast still is Roden Crater, with the Little Colorado River gorge in the background. People familiar with this area will also note the dark colored lava flow in the far upper right-hand corner that may have come from near Merriam Crater to the Little Colorado River (see more about this below).

Zooming in on Roden Crater.

Right over Roden Crater with the wing-tip (upper right) titled almost to vertical for the view. The circular feature in the center of the vent area is a large work of art that is being constructed by James Turrell. You can view images from the ground here. I haver has the pleasure of touring the site and it is incredible but not yet open to the pub lic.

Remember the lava flow from the first Roden Crater image above? Well that flow extends from its source for seven miles to the north where it intersects and crosses the channel of the Little Colorado River, running in this image from right to left (southeast to northwest). The gorge of the river is about 200 feet deep here and when the flow arrived at the lip of the gorge, red hot lava began to pour into it eventually blocking it. The river was forced to find a new channel around the lava dam and in the process created Grand Falls.

I include a ground photo of Grand Falls here, taken on March 2, 2008. Water from the Little Colorado River flows over the Permian age Kaibab Limestone as it re-enters its original channel downstream from the lava dam. The lava dam can be seen at the bottom of the photo and in the far upper right. Note the vehicles and people for scale standing on top of the lava dam near the upper right edge of the photo.

Back in the air with Ted we look downstream from the lava dam to the northwest. Note a former channel of the Little Colorado River opposite (right of) the sharp bend in the modern channel. It is a linear feature likely filled with dark-colored tephra (cinders) from Sunset Crater. Abandonment of this channel occurred some time before the modern channel was deepened.

Strawberry Crater and its lava flow. The typical cycle for these eruptions is: 1) magma is extruded into the air forcefully as droplets by the contained gas; 2) the droplets cool and fall around the vent as tephra, scoria or cinders creating a scoria or cinder cone; 3) the magma eventually becomes degassed and lava then wells up inside the newly created cone; 4) eventually the lava "pool" leaks out of the cone to create a lava flow. Most of the features here in northern Arizona show this sequence of events.

Colton Crater with its resurgent cone (located on the shadow line) within the much larger obvious cone.

Colton Crater below and SP Crater in the distance. Let's go have a look!

SP Crater is obviously a more recent feature due to its fresh appearance on the landscape. Not enough time has elapsed for soil to develop on it or its lava flow. The rest of the area is also underlain by lava rock but those features are much older and have more soil. Thus, the golden grass grows on top of the older features and highlights the relative recent nature of SP Crater.

Great view from right on top of SP Crater. Note how the degassed lava pool that was in the crater leaked out such that the flow extended about four miles downslope to the north.

View of the lava flow only with SP Crater out of view on the right. When the lava flow was active, the margins of the flow cooled first as they were pushed outward. This created natural lava levees that contained the hot flowing lava within. However, in two places this lava overtopped the natural levee toward the west. You can clearly see here two extra lobes of lava that broke through the main levee and traveled downslope into a valley, only to cool and consolidate here.

Turning around over Colton Crater and heading to the main volcano - San Francisco Mountain.

The Arizona Snowbowl ski runs on the slopes of Mt. Agassiz. Mt. Elden is in the background.

The highest mountain is Mt. Humphrey's at 12, 633 feet. I have hiked to the top many times. The San Francisco Peaks are the collapsed remnants of a once much higher cone, perhaps 3,000 feet higher and known as Mt. Coconino.

Coming in on Sedona 3 with glide power. There was not enough thermal lift on this winter day to do much gliding (ratio on this craft is about 30:1) but we did glide from beyond the Mogollon Rim into Sedona. Quiet and fabulous. Many thanks to Ted Grussing who graciously took me up on this fabulous day. Ted, I cannot wait to see what else excites up there!

Some facts about Ted Grussing's Lambada Motorglider:


Wingspan 15 meters with a glide ratio 30/1, or about 6 miles per thousand feet. Empty weight is 750 lbs. (includes oil in engine but not fuel). Two-seat side by side powered by a Rotax 912 ULS 100 HP engine. It is a tail dragger with steerable rear wheel. My normal initial climb rate when alone on an average air density of 6,000' is about 1700 fpm. I have the version with flaperons and it is very sensitive on the stick. Made in the Czech Republic by Urban Air now producing second generation as the Sundancer. Two wing tanks have useable fuel of about 26 gallons giving a range of about 1000 miles under power. Usually cruise cross country at about 80 kts air speed at 12,000' or higher giving me a ground track around 100 kts or about 115 mph and burning about 2.5 to 3 gallons of fuel per hours. My longest pure gliding flight in this ship is around 300 miles +/-.

Wednesday, December 31, 2014

Southern California's Blackhawk Landslide - An Impressive Catastrophic Event and Deposit - A Final 2014 Blog Posting

I wish everyone a Prosperous and Happy New Year in 2015! Thank you for reading Earthly Musings.

My wife and I recently visited relatives for the holidays in southern California and to break up the monotony of eating way too much food and visiting with people in indoor (TV) settings, we took a trip to the Mojave Desert and the Blackhawk Landslide. Ever since I was made aware of this huge feature, I have wanted to see and visit it. The best way to view the slide is from the air and since we did not have our own plane or drone delivered by Santa Claus, I include images found on the web. My images taken on the ground during our visit are also shown after the aerial pictures.

View to the northwest of the Blackhawk slide which is the lobe-shaped feature in image center
Photo credit: USGS web site: http://geomaps.wr.usgs.gov/archive/socal/geology/transverse_ranges/index.html
View to the south of the Blackhawk slide - hummocky terrain in image center
Photo credit: USGS web site: http://geomaps.wr.usgs.gov/archive/socal/geology/transverse_ranges/index.html 
Closer in view of the Blackhawk slide with the San Bernardino Mountains in the background 
Photo credit: Kerry Sieh. Image found on: http://www.lucernevalley.net/history/blackhawk.htm
This is how the Blackhawk slide looks from the air. But before humans could take to the sky, how was the slide recognized? It was by looking at the rocks found upon the odd, hummocky mass and taking note of their size and texture, and the mapping the extent of these rock types. It would be easy to see something like this from the air first and make an interpretation that could be verified on the ground. But the slide was first described by Woodford and Harriss in 1928 before the advent of common flight, who likened the deposit to one left by a large landslide in Elm, Switzerland in 1881. It was not until 1959 that Ronald Shreve completed his dissertation at Cal Tech, revealing that not only was this a catastrophic slide from the San Bernardino Mountains but that it was emplaced on a trapped cushion of air that ran out over the alluvial fan at over 50 miles per hour (80 km/hr).

MapQuest image of the San Bernardino Mountains and the Blackhawk slide (yellow). Faults are shown as red lines, with cities: Victorville, red circle; Lucerne Valley, blue circle; and San Bernardino, white circle. As the western edge of the North American plate is shoved by the impinging San Andreas Fault, the San Bernardino Mountains are upthrust to the north.
First, an introduction to the area is in order. The San Bernardino Mountains have been uplifted in the last 5 to 7 million years as the San Andreas fault impinges on this westernmost edge of the North American plate. Volcanic rocks erupted near Victorville in the Middle Miocene (12 to 15 Ma) are also found as clasts in fluvial deposits near Lake Arrowhead on top of the range. This means that before the San Bernardino Mountains were uplifted, drainage was to the south.

The San Bernardino Mountains in the background (south) have been thrusted up and toward the viewer. The thrust fault breaks the surface at the base of the mountains where the rock mass has been shoved up and north many miles over the desert floor.
Photo credit: USGS web site with annotations by Wayne Ranney

The thrust fault at the base of the northern San Bernardino Mountains is shown in the photo above. This upper block is composed of metamorphosed limestone and dolomite (marble) that is Pennsylvanian in age (about 300 Ma). These rocks correlate in time with the Supai Group in Grand Canyon and the Bird Springs Formation in the Mojave Desert. The thrusting pushes these relatively weak rocks out into open space in the Mojave Desert. Thus the Blackhawk slide is the consequence of rapid thrusting of weak rock that has collapsed into the desert.

Annotated image showing the Blackhawk slide and its source area in the San Bernardino MountainsPhoto credit: Kerry Sieh with annotations by Wayne Ranney
Now let's take a look at the Blackhawk slide on the ground. These photos were taken on our visit there on December 22 where we met Dr. Norm Meek of Cal State San Bernardino University.

We stopped on California Highway 247 to observe the distal end of the slide. It is the low hills on the skyline. The Blackhawk slide is about 5 miles long and 2 miles wide (8 km long and 3 km wide). It is between 30 and 100 feet thick (10 and 30 m thick).

Norm points out the slide with the western margin of the San Bernardino Mountains in the far distance.

We drove on a small mining road to the top of the slide. In the distance you can observe light colored disturbed areas where the Pennsylvanian age carbonates are being mined for cement.

Close-up view of the carbonate mine at the base of the San Bernardino Mountain. The thrust fault is below the lowest seen mine. Photo by Norm Meek.

Here is an exposure of the limestone on top of the slide. Note the original bedding which is still intact.

View to the north and the source area of the slide on Blackhawk Mountain. Note the light colored area beyond the closest yucca plants. This is where radiocarbon dates on freshwater (pond deposits) gastropod and pelecypod shells were obtained giving an age of about 17,400 + 550 years for the slide. Dr. Meek thinks that native carbon in the slide breccia may make this date too old and he suggests an age of around 14,000 years. It is interesting to speculate if the slide was purely from a gravitationally unstable overburden on the thrust. Or was it activated by seismic processes either from the thrust itself or movement on the San Andreas fault. Or was it facilitated by the pluvial Pleistocene climactic conditions at the time? Or could it be a combination of all three playing into its ultimate collapse?

The undisturbed upper surface of the slide looking northeast.

An small quarry on the northwest lobe of the slide provides both a view into the interior of the deposit and a blight on the slide. Shouldn't the geologic community petition for this feature to be set aside as an "Area of Special Geologic Interest?" It is located on BLM land and certainly there are other nearby areas to obtain gravel or marble for the construction business.

I enjoyed seeing an interior outcrop of the slide but the quarry looks to be a fair place for parties, trash disposal and general disrespect.

The wall of the quarry shows the near 100% composition of the clasts as Pennsylvanian marble. Helen and I enjoyed our short visit to the Blackhawk landslide. This is one of the largest such landslides that was mobile on a cushion of trapped air. It deserves to be protected and I hope you get to visit it one day. Happy 2015 everyone and thanks for reading!

Thanks to Dr. Norman Meek who took time out from his holiday to show us around. For a great outline of the geology of the San Bernardino Mountains, check out this USGS web page.

References

Woodford, A.O., and Harriss, T.F., 1928, Geology of the Blackhawk Canyon, San Bernardino Mountains, California: University of California Publications in Geologic Sciences, v. 17, p. 265-304.

Shreve, R.L., 1968, The Blackhawk landslide: Geological Society of America Special Paper 108, 47 p.

Shreve, R.L., 1987, The Blackhawk landslide, southwestern San Bernardino County, California: Geological Society of America Centennial Field Guide - Cordillera Section, v. 1, p. 109-114.

Saturday, December 20, 2014

I Have Some Exciting Trips Planned in 2015 - Join Me!

Many of the readers of this blog have traveled with me before to learn a bit about earth history and the evolution of landscapes. In 2015 I have a fantastic line-up of trips planned, both internationally and here in the Southwest. You can view a pdf of all of my trips here. There is no better way to travel than with your own personal geologist to explain what you are seeing. I hope to see you in 2015!

The Grand Canyon of the Colorado River - April 9 to 16 and August 22 to 29, 2015

The Green River in Canyonlands National Park - May 17 to 26, 2015

Imagine Flying Around the World on a Private Jet! Mongolia, Lake Baikal, Spitsbergen, Iceland, Greenland and more - June 9 to 30, 2015

Patagonia with Smithsonian Journeys - February 27 to March 16, 2015

Alaska River Adventure - The Tatshenshini River - July 16 to 30, 2015