Friday, August 31, 2012

another year older

In the Company of Plants and Rocks has been blogging happily for a little over a year now, and so in the tradition of things (according to Metageologist Simon Wellings) I’m including here links to my more popular posts, and then my own favorites -- also popular, but not so much.  Like Metageologist, I’ve really enjoyed myself, and I think my writing has benefitted a lot.  I've learned so much about plants and rocks, and many other things as well.  Perhaps best of all, my enthusiasm for things botanical and geological has soared, thanks to kindred spirits in the blogosphere.

Now, I’m taking a short sabbatical, due to post-field season reports and the promise of a road trip after deadlines are met.  In the meantime, I will continue to follow and read my favorite blogs ... so keep posting everybody!

Most Popular
My most popular posts according to Blogger stats are (highest first, adjusted somewhat for date of posting, out of 135 total):

The Myth of Frozen Waves (ice, Laramie Basin)
Taxonomy of Agaves and Vino-mezcal  (agave, botany, mezcal, tequila)
Jack Frost’s Latest Artwork (hoar frost, ice crystals, Jack Frost, snowflakes)
Sunstone: Compass of the Vikings? (Iceland spar, sunstone, vikings)
El Tío -- god of underground miners (Bolivia, Diablada, El Tío)
Leaving Home (Glycyrrhiza lepidota, seed dispersal, wild licorice, Wyoming botany)
Will the real Yam please stand up ...  (sweet potato, taro, yam)
Trip Plans: the amazing Expanding Great Basin! (Basin and Range geology, Great Basin)
Still Life with Pebbles (California geology, life, pebbles)
High Desert Trees (desert trees)
Geology -- Antidote to Civilization (Accretionary Wedge #46, geology, life)
Apparently posts with information of wider interest have more staying power.  My road trip adventures seem to be less popular over the long term.

My Favorites
These are the posts I most enjoyed putting together, very roughly in order of pleasure:

We too are ephemeral ... just like mountains. (Colorado geology, Cutler Formation, Fisher Towers, Uncompahgre Uplift, Utah geology)
Plants & Rocks: ferns and granite ... and climbers... (Asplenium, Black Hills Needles, Herb and Jan Conn, rock climbing, spleenwort)
Trip Plans: the amazing Expanding Great Basin! (Basin and Range geology, Great Basin)
Still Life with Pebbles (California geology, life, pebbles)
but there s life in the old dame yet (bristlecone pine, California botany, Pinus longaeva)
The many views of Devils Tower (Black Hills geology, Devils Tower, Wyoming geology)
Paradox Exposed (halokinesis, Onion Creek salt diapir, Paradox Basin, salt tectonics, Utah geology)
Jack Frost’s Latest Artwork (hoar frost, ice crystals, Jack Frost, snowflakes)
What’s an old oak for? (California botany, coast live oak, life, Quercus agrifolia)
Plants and Rocks: columbines and granite (Aquilegia laramiensis, Aven Nelson, Laramie columbine, Laramie Range, Wyoming botany, Wyoming geology)
The Spiritual Side of Mud (adobe, mission church, mud)
Taxonomy of Agaves and Vino-mezcal (agave, botany, mezcal, tequila)
All My Relatives are Miocene Fossils (Channel Islands, island ironwood,Lyonothamnus, plant fossils, trees)

Wednesday, August 29, 2012

South Dakota’s contribution to the Death of Flat Earth

The Fall of Icarus, 17th century, Musée Antoine Vivenel; from Wikipedia.

For Accretionary Wedge #49, Out of this World, Dana Hunter of En Tequila es Verdad asks us to “head for other worlds” and write of geology from there.  But it is only recently that we have been able to do this.  Of course, several thousand years ago Icarus flew from Earth on wings of wax and feathers that his father constructed for him.  He actually got close enough to the Sun that his wings melted so he must have had some amazing views. But he plummeted to Earth and drowned in the Icarian Sea (right, click to view), and so we have no record of what he saw.

I suppose the story of Icarus teaches a lesson about the dangers of over-ambition, hubris, arrogance.  Fortunately, the drive and curiosity of the human race are irrepressible, and many years later, as soon as technology allowed, mankind was back in the air trying to go higher and higher, to see what could be seen.

In 1934, Capt. A. W. Stevens, Capt. O. A. Anderson and Maj. W. E. Kepner  of the US Army Air Corps almost met the same fate as Icarus when they ventured too far from Earth.  Instead of wings, they traveled suspended under the Explorer, a high-altitude balloon.  The launch site was a small deep valley in the Black Hills of South Dakota, christened “the Stratobowl” (aka Stratosphere Bowl) -- over 400 ft (120 m) deep, walled on three sides by steep slopes capped with limestone rimrock, and with a half-acre (200 sq m) meadow in the bottom.  This would be an excellent wind-free place for the balloon and its passengers to leave Earth.
South Dakota's Stratobowl is located about 1.5 miles north of US Highway 16 roughly 10 miles southwest of Rapid City.  Aerial view below from ArcGIS online; note peace symbol in bottom of bowl in closeup.
The balloon was launched successfully on July 28, 1934, and things went fine for awhile.  Then after seven hours of flight, the crew noticed erratic behavior, holes in the bottom of the bag, and gas escaping.  They went into a free-fall, the balloon was torn to pieces in the process, and finally the hydrogen gas exploded.  Amazingly, the three men bailed out and landed safely, uninjured.

The next launch, of a safer helium-filled balloon, was made on November 11 of the same year, and was watched by 20,000 spectators at the site.  A new world record for manned flight was set when Explorer II reached 72,395 ft (22,066 m).  Anderson, Kepner, and Stevens became the first humans to view the curvature of the earth, and then returned safely home, landing in a field 225 miles east of the launch site.  Stevens documented the Earth’s shape with a color photograph, the first taken from the stratosphere.
Photo of balloon launch at the Stratobowl by H. Lee Wells, Jr.

Additional Information

National Geographic co-sponsored the flights.  Read about the First High-Altitude Photo and the flight of the Explorer II at their website.

The Stratobowl has been featured at Earth Science Picture of the Day.

If you’d like to visit, Outdoors in the Black Hills posted about the Stratobowl Rim Trail.

Monday, August 27, 2012

The many views of Devils Tower

Ponderosa pine, against a backdrop of massive columnar jointing.
It’s impossible to ignore Devils Tower if it’s anywhere in sight -- to say it dominates the landscape is an understatement.  It’s huge, rising 800 ft above the sandstone platform on which it appears to sit.  It measures roughly 3000 ft around at the base, tapering with graceful curves to ca 800 ft at the summit.  For this rock monolith to be standing above the nearly-flat sedimentary rocks of the Belle Fourche River valley seems so improbable, and continues to strike me as very bizarre, even though I’ve seen it many times.
“It is somewhat of a geological puzzle, standing alone as it does, and rising directly out of a country entirely made up of sedimentary rock.”  Thomas Moran 1894
The west face -- 600 ft from shoulder to summit.
The Tower’s form is graceful, and suggestive of symmetry from certain perspectives, but it’s not symmetrical, not even close.  All you have to do is walk around it, fly over it, climb it or drive the nearby roads to appreciate the many different views.
Aerial view of Devils Tower, courtesy ArcGIS online.
View from grasslands in the northeast part of the park.
As one approaches Devils Tower, the fluted texture of it’s sides becomes apparent, and its beauty is even more striking.  Up close, the overall form of the Tower disappears from view, replaced by giant rock columns.  They can be 6 ft or more across, and many are hundreds of feet tall with few horizontal fractures.  According to the literature, Tower columns typically are 5-sided but may have as many as 7 sides or as few as 4.  [I wonder who did the inventory, and how.]
Why columns?  As the Park Service explains, when the magma that formed Devils Tower cooled and began to solidify, it shrank and cracked.  Cracks grew out and down, intersected other cracks, and formed columns.
From bottom to top, there are notable changes in the structure of the Tower.  The base or shouder is massive, up to 100 feet in height.  Immediately above it are large columns that lie close to horizontal.  Moving up, the columns curve and become “vertical” ... but not quite.  They taper upwards, some ending, some merging, and so the walls slope inward, generally 75º to 85º.  The upper part of the Tower is much more fractured, vertically and horizontally.  The rock is less sound, cracks are wider, and pigeons (rock doves) and pack rats nest there.  The summit is rounded, covered with grass and sagebrush, and feels like a hill top.  Only from a few places around the edge are there precipitous views.
View from the south.  The leaning column of the Durrance Route, the "easiest" route on the Tower, can be seen about a quarter of the way in from the left edge, just above the curving lower columns (click to view).
View from halfway up the west face amid not-quite-vertical columns, looking down on curving columns near the base and talus field below.
The upper third of the Tower is more fractured.  Maybe it was exposed to erosion longer, or cooled under slightly different conditions ... another of the many mysteries.
And what's on top? ... plants and rocks!

The base of the Tower is surrounded by fallen column fragments.  Many are large and boulder-hopping is a challenge.  Most of the talus lies close to the base, though scattered boulders dot the slopes all the way down to the Belle Fourche River.

Below:  Large fallen column along the Tower Trail, just above trees; note tiny tourists on either end (click to view).
Phonolite porphyry of Devils Tower.
The rock that makes up Devils Tower is phonolite porphyry, part of a “continental phonolite-trachyte-quartze latite igneous association” (Halvorson 1980).  I know so little about petrology that I will go no further in this discussion, except to share a possibly mythical fact about phonolite porphyry.  When I was a ranger naturalist, back in the day, the Devils Tower Visitor Center was furnished with a giant box, The Admatic, that played a short slide show about the park every time a visitor pushed the button.  Obviously, those of us at the desk heard that program over and over, especially on busy days.  After three years, its phrases were pretty much hard-wired in my brain, most notably:
“phonolite porphyry, named for the ringing sound the rock makes when struck”
In fact, it was still in my head walking around the Tower thirty-plus years later, so I decided to put the authority of The Admatic to the test.  Sorry to say, the closest I could get to a ringing sound was a metallic “plink”.

The Origin of Devils Tower -- also many views

With its distinctive structure and rock type, surely the Tower’s origins would be decipherable by geologists.  But the words that William L. Effinger wrote in 1934 still apply:
“There is a good deal of uncertainty concerning the mode of origin of Devils Tower and the type of igneous body it represents.”
Effinger was employed by the Park Service under the Civil Works Administration to compile “such pertinent information as will be helpful in the preparation of geological museum exhibits at Devils Tower National Monument and more specifically to outline the story to be interpreted by such exhibits.”  Too bad the story wasn’t more clear.  Much of the material below comes from Effinger’s review paper, available at ParkNet.
Bear Lodge Butte or Mato Teepee, viewed from the west, Bear Lodge Mountains in distance.  Woodcut from Newton and Jenney (1880).
The first to formally describe Devils Tower were Henry Newton and Walter Jenney, who visited the Black Hills in 1875 with a military expedition led by Lt. Col. Richard Dodge.  They described the Tower, then called Bear Lodge Butte or Mato Teepee, as a “great obelisk of trachyte”.  They noted that the various igneous bodies of the region appeared to have been forced up through sedimentary strata which were upturned around them.  They found no evidence of volcanic activity.

Carpenter (1888) considered Devils Tower to be the remnant of a volcano, calling it a volcanic plug.  Russell (1896) concurred, but recommended the term plutonic plug.  Pirsson (1894) disagreed; he felt that volcanic origin and the shallow cooling it implied were unlikely, due to the Tower's massive columnar structure.  He suggested it was a remnant of a much larger and possibly laccolithic body.
View from the southeast.  Click to view remains of a wooden stake ladder to the summit, built by local ranchers in 1893, and fixed up by the Park Service in 1976 (near middle of face).
Jagger (1901) also concluded that Devils Tower, along with the Little Missouri Buttes to the west, were the remains of a large laccolith, no longer connected due to erosion.  He believed that massive columns required slow cooling deep underground; the neck of a volcano would have been too shallow.  However, Darton (1909) pointed out that prominent columnar jointing had been found in volcanic stocks in northwest New Mexico.  In addition, he considered the amount of erosion proposed by Jagger unlikely.  For these reasons, Darton favored volcanic origins.

Effinger (1934) ended his paper concluding that it was most reasonable to view Devils Tower as a remnant of a small independent laccolith.  He drew this diagram (right) to illustrate his take on the Tower's origins (click to view).
Northeast face.
Aside from Effinger’s review, Devils Tower received little attention from geologists from 1909 until the mid-1950s, when Robinson (1956) compiled a detailed map of the area.  He concluded that the Tower “is a body of intrusive igneous rock, which was never much larger in diameter than the present base of the Tower, and which at depth (1000 ft or more) is connected to a sill or laccolith type body.” (A well drilled in a structural dome between the Tower and the Little Missouri Buttes had hit phonolite at 1400 ft).  He also made clear that much uncertainty remained:  
“even today after detailed geologic mapping of the area, no conclusive proof of its mode of origin can be presented.”
The volcanic stock hypothesis did not die, however, and in fact made a strong comeback in 1980 based on work by Halvorson.  He cited as evidence the presence of alloclastic breccia with a volcanic glass matrix, the depressions surrounding both the Tower and the Buttes probably representing collapsed magma chambers, contemporaneous volcanic activity nearby, and the clear resemblance to known volcanic necks, like those in New Mexico pointed out earlier by Darton (1909).

Most recently, Zavada et al. (2009) suggested that Devils Tower is the remnant of an eroded lava lake “emplaced into a broad crater of a phreatomagmatic volcano”.  Their conclusion was based on suspected phreatomagmatic units around the Tower, gravimetric studies and modeling.  They proposed that columns formed by cooling on "two thermal fronts originally representing the bottom and flat top of the original phonolite lava lake."
View from the north ... of the remains of a phonolite lake?  How do we explain that to the public??

So in spite of its distinctive structure and composition, and much study, the origin of Devils Tower remains a puzzle.  The debate continues over the nature of the intrusion -- shallow or deep? volcano or laccolith?  Meanwhile, 400,000 people visit Devils Tower National Monument every year.  Many take photos, and quite a few pay the money to drive up to the Visitor Center where they can buy a few souvenirs before they head off to Mt. Rushmore or Yellowstone, their next stop.  A minority walk around the base, looking up in awe.  I suspect only a tiny percentage contemplate the origins of this improbable rock.

But in my cynicism, I tend to underestimate visitors and their appreciation of Devils Tower.  One evening in the campground, I watched as folks set up their tents (yes, there still are many tent campers) and arranged table cloths and dinnerware on their picnic tables.  A man was on his phone with a child at home, trying really hard to share his excitement:  “You aren’t going to believe where I am! ... can you guess?  I’m looking at a giant rock!!  [pause]  you don’t know?!! get your mother ... she’ll know!”  Mom did know, and got to hear how unbelievably huge and beautiful and mysterious Devils Tower really is.

The many faces of Devils Tower, courtesy Google Images; click to view.

Literature Cited

Carpenter, F.R.  1888.  Notes on the geology of the Black Hills. Prelim report of the Dakota School of Mines, Rapid City.

Darton, N.H.  1909.  Geology and water resources of the northern portion of the Black Hills and adjoining regions in South Dakota and Wyoming. USGS Prof. Paper No. 65, pp. 68-69.

Effinger, W.L.  1934.  A report on the geology of Devils Tower National Monument.  Berkeley, CA:  National Park Service, Field Division of Education.  Available at:

Halvorson, D.L.  1980.  Geology and petrology of the Devils Tower, Missouri Buttes, and Barlow Canyon area, Crook County Wyoming: Grand Forks, University of North Dakota, Ph.D. thesis, 218 p.

Jaggar, T. A. Jr.  1901  Laccoliths of the Black Hills. 21st Ann Rep, USGS, Pt. 3.

Moran, Thomas.  1894 (January).  Artist’s adventures.  A journey to the Devil’s Tower.  The Century Magazine pp 450-455.  Available at:

Newton, H. and Jenney, W.P.  1880.  Rept. on the geology and resources of the Black Hills of Dakota. U. S. Geographic and Geologic Survey of the Rocky Mountains Region. Washington.

Pirsson, V. L.  1894.  Description of the character of the igneous rocks making up Mato Teepee and the Little Missouri Buttes.  Amer. Journal Science, Vol. XLVII, pp. 341-346.

Robinson, C.S.  1956.  Geology of Devils Tower National Monument, Wyoming.  USGS Geol. Surv. Bull. 1021-1.  Available at: 

Russell, I. C.  1896.  Igneous intrusions in the neighborhood of the Black Hills of Dakota.  Journal Geology.  Vol. 4.

Zavada et al.  2009.  On the geological origin of Devils Tower, Wyoming; a new hypothesis constrained by field research, analogue and thermal modeling data, and gravimetric survey.  Abstracts with Programs - Geological Society of America 41: 444.

Wednesday, August 22, 2012

My world is turning yellow

Bracken fern, Pteridium aquilinum
It’s mid-August in the Black Hills, and the time has arrived for yellow things.  But it has been such a hot summer that the sudden cold nights and yellow bracken caught me by surprise.  Lots of other plants are preparing for change as well.  Stands of paper birch have become mosaics of green and yellow.  Leaves flutter in the light breeze and float to the ground.
Paper birch, Betula papyrifera
See the falling leaf?  just right of the leftmost birch ...
I had no luck whatsoever catching falling stars during the recent Perseids “shower”.  I fared only a bit better at catching falling leaves (above), but at least I saw plenty of them, sailing through the air, beginning to cover the ground.

Hop hornbeam,  Ostrya virginiana
Leaves of hop hornbeam (ironwood) are still green and lush, but the elegant fruiting clusters are drying to buff, tan and yellow-brown.
Hop hornbeam nutlets are enclosed in inflated papery bracts.
Boxelder, Acer negundo
The boxelders are now decorated with clusters of yellow-green paired samaras (aka whirlybirds or maple keys).  In spite of their compound (divided) leaves, boxelders are indeed maples -- their samaras give them away.
Whirlybirds ... paired samaras, each of which contains a seed.
Boxelder bug on boxelder samaras ... this bug knows his place in the world.
The wild plums also are yellow ...
Wild plum, Prunus americana
... and a bit further down the trail, they're red!  Shake the little tree and the edible ones fall to the ground.  Luckily they are early this year.  Often wild plums here don’t ripen at all, as frost gets them first.

At lower elevations, it will be awhile before there are yellow leaves on trees.  But the wildflowers make up for it -- they are mostly yellow this time of year.
Curly-cup gumweed, Grindelia squarrosa, lines the roadsides; flowers (heads) ca 0.5 in across.
Velvety goldenrod, Solidago mollis, thrives in a prairie dog town.
There are lots of yellow composites in this dog town, like hairy golden aster, Heterotheca villosa
... and lacy tansy aster, Machaeranthera pinnatifida, above and below.

And here are my friends, the sunflowers, facing east to greet the morning sun.  What is that curious thing behind them?

ah hah ... it's a giant rock!
Wild sunflowers (Helianthus annuus); Devils Tower in background.