Saturday, October 30, 2010

A Bullet and A Fossil ~ Geology and the U.S. Civil War

During the U.S. Civil War, geology often set the stage and the direction for battle.  A small incident at the Battle of Wilson’s Creek (Missouri, 1861) involving a bullet and a fossil led me to this realization.  It’s embarrassing to admit it was really new to me despite having been a Civil War buff for years.  As I discovered, the intersection of geology and war has been the stuff of articles, conferences, and books (see, for example, Studies in Military Geography and Geology, edited by Douglas R. Caldwell, et al., 2004).  As one set of authors in another work puts it (citing still another author),
There are geological aspects of just about every battle on land, including those of the American Civil War.
(J.T. Hannibal and K.R. Evans, Civil War and Cultural Geology of Southwestern Missouri, Part 1:  The Geology of Wilson’s Creek Battlefield and the History of Stone Quarrying and Stone Use, in From Precambrian Rift Volcanoes to the Mississippian Shelf Margin: Geological Field Excursions in the Ozark Mountains, 2010 p. 45)
The underlying geology of the land over which the Civil War armies moved and fought is of interest, not just the geography of the surface of that terrain.  Geology explains why the landscape is the way it is and how that influenced the conflict.  It tells not only why mountains stand and rivers run where they do, but also why roads and railroads were likely to have been laid down where they were, why certain mountain gaps or passes were appropriate for moving wagons and artillery and others not, whether some hills on some battlefields were more defensible than others, and so on.  But, to be candid, the geology/geography distinction in this context is still blurry in my mind.

Even someone with only a passing knowledge of the Civil War is likely to know some portion of the litany of famous geological features of different battles, pivotal places on these battlefields which men struggled and died to attain or defend.

One of those famous geological features appears in the picture below, taken by Timothy O’Sullivan shortly after the Battle of Gettysburg in early July, 1863.  It shows Union defensive positions on Little Round Top, located to the southeast of the town of Gettysburg, Pennsylvania (Big Round Top is in the distance).  The success of Union forces in holding this rugged, steep hill on the left of the Union line during the battle was instrumental in the ultimate Union victory.  (The source of the photo is the Library of Congress.)

According to Andrew Brown, in his short and absorbing Geology and the Gettysburg Campaign (Commonwealth of Pennsylvania, Department of Conservation and Natural Resources, Educational Series 5, 1962), Little Round Top is part of a diabase sill, an outcropping of rock that intruded perhaps 200 million years ago into the Triassic sandstone of the Gettysburg Formation.  This diabase is described in a geologic map from the Pennsylvania Geological Survey (1980) as “dark gray, medium to coarse grained.”  The material making up these diabase outcroppings is more resistant to erosion than the rock that was originally above it or surrounding it.  As a result, the outcroppings stand above the plains that fall away on each side – hence their military importance.  The Union forces occupied a fish hook-shaped position anchored at one end by Little Round Top; in effect, the entire line was on this diabase sill.

Brown's booklet outlines “the extent to which the movements of the two armies toward Gettysburg, and the battle itself, were influenced by the geology of the region in which the campaign was conducted.”  (p. 1)  These influences played out, not only in which features of the terrain on the battlefield were contested by soldiers, but also in how the armies moved across the Virginia, West Virginia, Maryland, and Pennsylvania landscapes, and why an encounter in the Gettysburg basin became increasingly likely.

The geology of the land exerts its influence in another deadly way when bedrock lies fully or nearly exposed.  The defenses in the photo above consist largely of some extant walls of piled rock and diabase boulders.  This was the largely the only protection on Little Round Top and for much of the Union position.  As a result, casualties were dramatically greater for the Union defenders of this higher ground than was the case in most other battles in which forces defended elevated positions.  Why didn’t the soldiers use trenching tools and erect more substantial defenses?  As Brown explains,  “The resistant diabase sill is so close to the surface that it was impossible for the soldiers to ‘dig in,’ . . . . “ (p. 13)

As will be evident shortly, that brutal influence of geology is a natural segue to the Battle of Wilson’s Creek, getting us closer to the genesis of this posting.  The battle took place on a rolling Missouri landscape of the western Ozarks, captured in the newspaper illustration below showing Union General Nathaniel Lyon leading a charge of the First Iowa Regiment.  A key feature of the battlefield, a ridge that would become known as Bloody Hill, is what I think is seen in the background.  (The immediate source of this image is the Library of Congress and was copied from Frank Leslie’s Illustrated Newspaper.)

In the early morning of August 10, 1861, General Lyon, tired of waiting for reinforcements to counter a growing Confederate threat to Missouri, took the fight to a numerically superior enemy commanded by Generals Benjamin McCulloch and Sterling Price camped along Wilsons Creek.  Lyon marched from Springfield and launched a surprise attack from the north.  With their initial success, Lyon’s men occupied the ridge that, over a four-hour period, would earn its new name.  But Lyon’s advance faltered on that exposed ridge in the face of artillery fire, triggering a vicious struggle for control of Bloody Hill.  The other component of Lyon’s plan, an attack by Union Colonel Franz Sigel from the south, failed.  Then Lyon fell, the first Union General to be killed in combat in the war.  The battle ended with the defeated Federal troops retreating to Springfield.

As for the geology of the event, the bedrock for much of the most contested portion of the battlefield is Lower Mississippian limestones of the Keokuk and Burlington Formation.  The 1987 geologic map for the area published by the U.S. Geological Survey describes these limestones as “light-gray to medium gray, coarse- to fine-crystalline, massive-bedded, crinoidal limestone.”  That last adjective confirms the expectation we have of limestones – there are fossils here.

This is also a karst landscape in which water has eroded the underlying limestone bedrock, creating such features as sinkholes and rocky protuberances.  This would directly affect the ebb and flow of the battle.  And geology extended here a gory hand similar to the one that was offered two years later at Gettysburg.  As Hannibal and Evans write,

The terrain, since it was developed on karst, was also uneven in places in what was at the time a fairly open area.  Glades [open areas with limestone bedrock very near the surface] . . . affected the battle, most critically at the knob that would become known as Bloody Hill.  The shallow depth to bedrock would also have an effect on the ability to dig entrenchments and gave an advantage to artillery. (emphasis added, p. 46)
I have an image of many artillery shells and bullets hitting expanses of limestone at or near the surface of Bloody Hill and elsewhere on the battlefield.  With what result?  Flying fragments of rock and metal, ricocheting bullets, and deformed spent bullets?

Earlier in this decade, the Midwest Archeological Center, part of the U.S. National Park Service undertook an archeological inventory of the Wilson’s Creek Battlefield.  This involved using metal detectors, as well as visual inspections, to identify and collect artifacts from the battle in as systematic a fashion as possible over as much of the battlefield as was accessible.  The effort, headed up by historical archaeologist Douglas Scott, resulted in an in-depth report published in 2008, entitled “The Fire Upon Us Was Terrific:”  Battlefield Archeology of Wilson’s Creek National Battlefield, Missouri (Technical Report No. 109)
Among the kinds of bullets recovered were .69 caliber spherical balls; these bullets were made of soft lead.  One of the 154 fired spherical balls found is the inspiration for this posting.  Scott’s report notes, in passing, that

One impacted ball retains an interesting impact scar that of a tiny fossil shell where it struck a piece of limestone.  (p. 40; the photo below, copied from the report, suggests what the authors saw)

Additional Source
In describing the Battle of Wilson’s Creek, I drew on Scott’s “The Fire Upon Us Was Terrific”  and, among several books, Michael Weeks’ The Complete Civil War Road Trip Guide (2009), a surprisingly detailed treatment of the events at many Civil War sites.

Sunday, October 17, 2010

Ghosts of Evolution Past

When the clock stops on a life, all things emanating from it become
precious, finite, and cordoned off for preservation.
                                ~ Jennifer Egan, Dealing With The Dead
Fall is an apt time to reflect on the past.  It’s a territory that should be labeled “Here be ghosts.”

In her short essay Dealing With The Dead (The New Yorker, October 8, 2010), novelist Jennifer Egan reveals her penchant for gathering and wearing “loans from the dead” – her grandmother’s fake pearl necklace, sweaters from her father and her stepfather.  This wearing in her daily life of mementos from departed loved ones, she calls “borrowing from the dead,” and considers it “a way of keeping them engaged in life’s daily transactions – in other words, alive.”  To me, it’s a way of calling the ghosts.

This loss of an individual person, the loss of that yin to your yang, is wrapped up in expectation.  The expectation that the person will, any minute now, walk into the room and resume the life recently ended.  I suspect Egan’s tokens keep alive those expectations, those ghosts, much longer than is true for most people.

And now for ghosts with still longer lives.

These ghosts are called by a certain autumnal smell.  Yes, there’s the usual constellation of scents that signals autumn for me, including the sweet scent of wood burning and the musty one of decaying leaves.  But, this is also the time of year when a remarkably different fall fragrance comes to mind.   For many years, during my commute to and from work, I walked past the southwest corner of the block that the U.S. Supreme Court Building occupies.  It was there, particularly on late afternoons in Indian Summers, that I’d frequently catch the whiff of that villain of autumn aromas, the one emitted by the malodorous fruit-like product of the female ginkgo (Ginkgo biloba).  Nearly everyone describes that odor by invoking either excrement or vomit (or more colorful synonyms).  A most vile seed and covering.

Last week, I retraced that commute I used to make, looking for ginkgos, sniffing for that fetid smell.  I found ginkgos, but not the ones that would have generated the odor at the corner of the Supreme Court building.  The ginkgos that I visited this time stand across the street on the lawn of the main building of the Library of Congress.  I assume these are male trees (pictured below) because there were no seeds on the trees or festering on the ground, although, it takes a very, very mature female ginkgo tree to produce the seeds.  (The small twig with leaves was lying at the foot of one of the trees.)

Here is a picture of the seeds that would have appeared were these females of the right age.  (The picture was obtained via Wikimedia Commons and is identified as the “own work” of Love Krittaya and in the public domain.) 

Has the female ginkgo that pungently punctuated my fall commute for so many years been removed?  Did she fall victim to the odor police or to all of the new security fences and other barriers that have taken over Capitol Hill?  Still, as I went over familiar ground, I found it easy to revive the memory of that smell.

The noxious odor is only one of this seed’s several offenses.  The pulp is laced with urushiol which can cause serious skin rashes, just as this chemical does when you encounter it in poison ivy.  The nut itself, though edible in small quantities, is well-armed with toxins – cyanogenic glycosides (eating uncooked nuts releases hydrogen cyanide, a perfectly nasty chemical suitable for a plot crafted by Agatha Christie) and 4-methoxypyridoxine (highly toxic for children, depriving them of vitamin B6 – not surprisingly, the top of the Google hit list for this compound is a piece entitled Ginkgo Seed Poisoning appearing in the journal Pediatrics)  The various ills of the ginkgo seed are nicely reviewed in the Washington Post’s Urban Jungle column for October 12, 2010 (on the Urban Jungle page, look for #2 (how appropriate) in October). 

When a resident of San Jose, California, recently posted a notice on Craigslist asking (well, almost begging) people to come and harvest the produce from the female ginkgo tree outside his house, he ended his posting with this desperate stipulation – “All I ask is that you take the entire fruit away with you, and not just the nuts.”  There’s no point getting technical when the smell of vomit pervades your home, but, the ginkgo is a gymnosperm, which means, I think, that technically it produces a seed with a covering, not a fruit, though, I doubt that I will be consistent with my terminology in this posting

The ginkgo tree is often referred to as a living fossil, having a lineage that, according to the University of California’s Museum of Paleontology (UCMP), traces back to the Lower Jurassic, some 190 million years ago.  During the Cretaceous Period (which ended some 65 million years ago), there were possibly a half dozen different ginkgo species.  But, then, in short order (in paleontological time), there was but one, Ginkgo adiantoides, its fossilized leaves “virtually indistinguishable from modern-day Ginkgo biloba.”  Some 9 million years ago the ginkgo slipped out of the North American fossil record, and, finally, completely disappeared from all fossils records, according to the UCMP, by the Pleistocene Epoch (beginning some 2.6 million years ago).  The many ginkgos populating our urban areas owe their existence to Buddhist monks in mountainous areas of China who cultivated the trees and may have saved the species.

But, there are startling ghosts summoned by the ginkgo seed.

In their 1982 paper in Science entitled Neotropical Anachronisms:  The Fruits the Gomphotheres Ate, Daniel Janzen and Paul Martin hypothesize that the seed dispersal systems of many Central American plant species evolved so as to give herbivore megafauna a key role.  Among these megafauna was the gomphothere, a four-tusked, large (at least some 2.5 tons) mammal that went extinct, according to the authors, along with many other megafaunal species in Central America about 10,000 years ago.  Under this hypothesis, the disappearance of these megafauna left their flora partners dependent upon less efficient alternate dispersal agents.  A prime piece of evidence is the vast overproduction of edible fruit by some tree species with the result that much of the fruit rots on the ground.  Other evidence includes the production of fruits rejected by extant dispersal agents.  Janzen and Martin argue that such fruiting traits are anachronisms, developed for a faunal partner that is now gone.

Martin and others like science writer Connie Barlow are more than happy to label the extinct faunal partners of these flora as ghosts.  Indeed, Barlow’s marvelous book exploring the Janzen/Martin hypothesis is entitled The Ghosts of Evolution:  Nonsensical Fruit, Missing Partners, and Other Ecological Anachronisms (2000).  Fruits that are too big, too tough, too toxic for contemporary dispersing agents are prime candidates for the anachronism label and Barlow writes joyfully of her exploration of these flora and their ghosts.  How can one resist this? – “Grocery stores are excellent places to encounter ghosts.  They lurk in the fruit section, feasting on anachronisms.”  (p. 7)  (Papaya and avocado are among the anachronisms being devoured.)

The concluding sentence of Janzen and Martin’s article is part of their effort to expand the potential reach of their hypothesis.  This sentence has nothing to do with the Pleistocene megafauna, but it brings us to the ginkgo and the ginkgo’s ghosts:

The vesicatory [i.e., blister causing] ripe fruits and weak-walled nuts of Ginkgo biloba might even have been evolved in association with a tough-mouthed herbivorous dinosaur that not chew its food well.  (p. 27)

Ah, the ginkgo’s ghosts – dinosaurs – which, except for the avian variety, disappeared at the end of the Cretaceous.  Barlow entitles her book’s section on the ginkgo, The Tree Who Remembers the Dinosaurs.  But, Janzen and Martin may have had the wrong ghost.  Barlow describes how Peter Del Tredici, currently Senior Research Scientist at Harvard University’s Arnold Arboretum, wrestled with this ghost and ultimately reached a slightly different conclusion.  In Barlow’s words,

The first set of target dispersers could have been small scavenging dinosaurs that lived during the Jurassic or Cretaceous.  As Del Tredici sees it, the odor of a ginkgo seed, after it has lain on the ground for a few days, may mimic rotting flesh well enough to attract scavengers of all stripes. . . . Pegging partnership on carrion-feeding rather than plant-eating dinosaurs solves one very big problem.  The seed is physically protected by a shell too thin to withstand contact with grinding machinery. . . . Herbivorous dinosaurs of the Mesozoic had two kinds of machinery that might have crushed a ginkgo seed.  Teeth would have been an obstacle in some, and for the rest, a stone-filled gizzard would have threatened even more injury.  (p. 142-143)

Barlow adds a cautionary note,

Peter Del Tredici is the first to admit the weakness of the evidence on which the dinosaur hypothesis is based.  Still, nobody has offered a better supported explanation for the mystery of the ginkgo.  (p.146)

So, there it is.  The expectant ginkgo tree, waiting for those scavenging carnivorous dinosaurs to gather up her stinking seeds and start them on their productive journey.  But now only ghosts heed the call and gather beneath her.

Thursday, October 7, 2010

Risks and Rewards of the Fossil Hunt – Evolution of a Cautionary Tale

Last week, roofers began work on a house up the street.  They moved easily along the peaks and valleys of the roof, a dangerous dance to the staccato of nail guns and the steady hum of a compressor.  They also prompted the reflection that life carries risks, some activities decidedly riskier than others.

The risks of hunting for fossils?  It certainly doesn’t rank up there with such avocational activities as free-style mountain climbing, the sport of scaling mountainsides without ropes and the other tools used by climbers more concerned about gravity.  (Tragically, a week ago, a star of this world, Kurt Albert, lost his life in a fall.)  Still, the risks of the fossil hunt, though modest, are not zero.

When I first started hunting for fossils in a serious way, I heard a cautionary tale that was then making the rounds of the local amateur paleontology clubs.  An experienced collector here on the East Coast was digging into a hillside when the soil above him collapsed, burying and killing him.  Tellers of this tale highlighted that he was collecting in a quarry alone and without permission.  They made it clear that the risks of digging deeply into a hillside went almost without saying.  He was a good man, they noted in passing.

Over time I’ve heard several other such tales of dire events on the hunt for fossils.  Yes, these stories may be salutary if they change risky behavior, but the more I’ve thought about them, the more depressing I find them because, in the telling, these accounts typically leave the life led to that point as an afterthought.

And then I found a few items on the web about Rene Savenye.  Though his story might well have the ingredients of a cautionary tale (so it began in my eyes), the more I learned about him, the more his story reassured me, reaffirmed the value of the life led, putting the events of his passing into proper perspective.

Savenye, a retired high school science teacher in British Columbia, was the quintessential citizen-scientist, a man excelling at his many and widely varied scientific interests.  He was, among many other things, an environmentalist, a mycologist (studier of fungi) and, of course, a committed amateur paleontologist.  Savenye, over his lifetime, amassed a rich and extensive collection of fossils, gaining recognition for the 1995 find of what is the second oldest fossil of a bee on record (early Eocene epoch), and the first found in Canada.  (A nice piece on Savenye appears in the online Victoria travel guide.)

On July 26, 2002, the 63 year old Savenye, hiking alone near Lake Louise and on the hunt for fossils, was struck and killed by lightning.  [Later edit:  I relied on the stories I found on the web, but see comment below for the likelihood that he was not actually hunting fossils.]  As an obituary put it, "he left us exactly the way he would have wanted, wearing his hiking boots, on top of a mountain (Mount Fairview near Lake Louise)."  (From a tribute to Savenye by the Vancouver Mycological Society.)

But, no, this is not just a cautionary tale about the weather and mountain tops.  Rather, his is a story that continues to remind me of the life, not the death.  Among the legacies he left are a dedicated cadre of former students.  Over 3,000 fossil specimens, about a third of Savenye’s first-rate fossil collection, are now a valued part of the holdings of the Royal British Columbia Museum).  In Blackie Spit Park (Surrey, British Columbia) where he worked to remove invasive plant species, he is memorialized by the Savenye Environmentally Sensitive Area.  A monument to him there reads:
A man who cared, a man who shared.
And his name lives on in another way.  That early Eocene fossil bee?  It’s a new species named in early 2003 by M.S. Engel and S.B. Archibald as Halictus? savenyei.  (The Canadian Entomologist, January/February 2003, abstract .)  Bruce Archibald, one of the authors, kindly sent me a copy of the journal article.  Its warm acknowledgement to Rene Savenye is another apt memorial:

We are grateful to the late R. Savenye for the donation of the specimen reported herein.  Rene was a well-known and loved British Columbian naturalist and avid [a]vocational paleontologist.  He donated and loaned a number of significant fossil specimens for study.  One of us (SBA) spent many pleasurable days collecting fossils with Rene.  It is a great pleasure to name this species in his honour, and we are grateful that he learned of this before his passing.  This contribution is dedicated to his memory.
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