Archive | September 2022

Claude Moore Park: How Geology Won the Civil War

That is a grandiose title and I admit it’s only part of the story. Nevertheless, the movement of General Lee’s Army of Northern Virginia was tracked from a lookout tower constructed on the ridge that bounds the northern margin of Claude Moore Park (Fig. 1), from where his troops were observed to be moving north, towards Pennsylvania. Because of this tactical intelligence, Union forces converged on Gettysburg and were able to repel the Confederate invasion. Most historians refer to Gettysburg as the high tide of the Confederacy.

Figure 1. Map of northern Virginia (left panel) and detail map (right panel) of Claude Moore Park. The labeled locations are where later photos were taken. The ridge is where the observation tower was constructed that tracked the Confederate troop movements prior to the Battle of Gettysburg.

The study area is located near the Potomac River, where it drops from the Appalachian Mountains to Chesapeake Bay (Fig. 1). The ancient rocks that underly this area have been deeply eroded by streams, producing a labyrinth of hills and valleys. This post begins at the Uplands (Fig. 1) and shows the dramatic change in both ancient and modern sedimentation that results from such a landscape.

Figure 2. (A) steep southern slope of the ridge that defines the park and the local drainage system. (B) The sediment here is Tertiary in age, and it is a typical gravel stream deposit, with rounded cobbles (up to six inches in diameter) in a matrix of sand and silt.

The ridge probably follows the erosion-resistant channel of a river, with coarser sediment forming uplands because it is resistant to erosion. It is like a topographic inversion; what was once low (the bed of a gravel river) is now high because cobbles are difficult to move by water that is no longer focused in a river channel.

Figure 3. (A) Typical lowland view of young trees and muddy areas filled with grass. (B) The sediment here is silt and clay. See Fig. 1 for location.

The slope reduces southward and drains into a pond (Fig. 1), which is simply the lowest topography and thus wet year round. However, the entire area labeled as “Wetland” in Fig. 1 is probably periodically inundated during wet times.

Figure 4. (A) Incised stream in the wetland, indicating continuing uplift during the Holocene. Note the thick underbrush in this intermittently submerged area. (B) Fine-grained sediment is dominant but small boulders (this one is about 12 inches in length) are distributed, left over from a previous high-flow environment during the Tertiary.

This post has shown how sedimentation can change over short spatial distances, and topography can become inverted. The wetland area was once the flood plain of a gravel river (e.g. Fig. 2), but the silt and clay that collects on a flood plain is easily eroded and weathered when it is exposed to the elements, creating local wetlands surrounded by ancient river beds.

This interpretation is speculative because bed rock is never far beneath the surface in northern Virginia. We saw no outcrops on the ridge, however, which doesn’t mean that there is no resistant rock beneath the gravel-covered slopes, but it is consistent (geologists love that word) with my interpretation. Further support for the ancient stream-bed hypothesis comes from the orientation of the ridge, which doesn’t follow the regional structural trend of NE-SW for basement rocks. Note that the Appalachian Mountains define this trend (see Fig. 1), as have all of the Paleozoic and Mesozoic rocks we have encountered in the area. The uplands (see Fig. 1) ridge is oriented east-to-west, which goes against the grain, geologically speaking.

Thanks to an ancient gravel stream, the Union army was alerted to the movements of the Confederate invasion and stopped them at Gettysburg. Geology saved the day again…

Review of “The World of Lore: Dreadful Places” by Aaron Mahnke

This was another random read, this time picked up at a local bookstore’s bargain table. I didn’t even read the back cover, so I had no idea this was a collection of mystical stories. The author has a podcast and seems to be a diligent researcher, and he presents a balanced picture of what can be explained and what cannot. I’m not a fan of this genre, but I found the stories well written and fun, with lots of background information on the places where the stories originated. Some of the tales made my hair stand up. Some were boring, most were informative and well presented.

It is an easy book to read, but for some reason it seemed to take a long time to finish. I mean, if you’ve heard one ghost story, you’ve heard them all; nevertheless, the depth of research and skeptical storytelling kept me interested. There really are unexplained incidents. That is a repeated message in this collection.

There isn’t much else to say. The book’s premise is clear and it is informative, rather than just retold stories. If you enjoy the lore behind the scenes, in many different locations, then I recommend this book.

I can’t help but wonder why such stories don’t occur today, despite the widespread use of smart-phone cameras and social media…

Review of “The Man Who Died Twice” by Richard Osman

I didn’t know this was part of a series when I bought it at Copenhagen International Airport. It wasn’t a problem, however, because the references to previous exploits are vague and don’t directly impact this story. The personalities and relationships of the characters are presented in sufficient depth that a fan of the series would probably find the detail redundant.

One thing I found disconcerting is the use of the present tense with a third-person narrator for most of the chapters. This approach is so awkward and inappropriate that the author kept resorting to the past and present perfect to present past events, and they made a lot of grammatically clumsy (if not erroneous) constructions doing it. It just made no sense. There is a first-person narrator who shares her view periodically, and that works fine in present tense. Some people talk like that.

As you can imagine, there are a lot of cliches (English not American) and stereotypes for the characters, but they kind of seemed the same to me most of the time. Now and then, one of them would suddenly behave differently than they had before; that is a risk with an ensemble cast of characters, and I only mention it to be as complete as memory will allow. The central character (not the narrator) seemed to have a rush of inspiration at the end, realizing her fallibility; it made me wonder if she does it in every book?

The plot was obvious because there really was only one person with the resources required to pull off the crime; thus, a variety of red herrings were introduced to keep the reader from figuring it out, and show the weakness of egotism (I still don’t understand the title).

Overall, a fun romp with some elderly people, filled with anecdotal observations of aging and nonsense. I didn’t finish it on the flight, but I remembered to read a few chapters (they’re short) every day.

A final comment: One crime solved by the “Thursday Murder Club” is enough for me…

Review of “The End of the World is Just the Beginning” by Peter Zeihan

Many knowledgable reviews of this book have been written, and it started a firestorm of debate about the impacts of globalization, and its demise. That is the premise to all 475 pages. It is stated in the Introduction and repeated at least once on almost every subsequent page. The problem is: the author never explains why America would suddenly stop supporting an international convention it helped create. It is treated as an axiom, a given assumption from which all kinds of predictions can be made. There isn’t the slightest attempt to explain, much less justify, this fundamental premise. Because of this glaring deficiency, the scenario described in detail for many countries and industries is no more than an alternate history of a world that hasn’t appeared yet, like if the Axis powers had won World War II.

The details are culled from Zeihan’s experience as an international consultant, and he has plenty of them. They are reasonable, given the axiom of unilateral American withdrawal from the international scene. The strengths and weaknesses of various nations are interesting and will, of course, contribute to the future economic development of those economies. So, the book is worth reading, as a summary of the history and current state of various economic sectors (e.g. mining, petroleum, agriculture), and it is worth having around as a reference, a partial explanation of global trends. No doubt, many of his predictions will come true because they are based on facts, even if not supported with a bibliography.

I have another complaint, however; there are no references, and the footnotes consist of often witty comments rather than details not given in the text. There isn’t even a list of supporting sources. Nothing. I guess we’re supposed to trust the author, as an expert. Nevertheless, if taken in a humorous light (a perspective apparent in the author’s comments), like a conversation on the front porch with a beer in your hand (maybe a rum and coke), it is entertaining.

I enjoyed reading it, but I’m taking his predictions with a grain of salt.