Southern Proceedings: The Three Tennessees

Tennessee geologic map
Geologic Map of Tennessee, courtesy of USGS

This post comes at you live(-ish) from the Symposium on Geophysics for Environmental and Engineering Applications (SAGEEP) 2018. SAGEEP 2018 is in Nashville, home of great barbeque, live music on every corner, and one of the best state flags in North America. I’ll get into the flag a bit later, it’s actually important for this post.

One good thing about going to a geological/geophysical conference is that the conferences and attendees tend to be very grounded in the location of the meeting itself–literally, there were entire sessions on the ground in Tennessee.

There are a lot of things I do/did not know about Tennessee, but one interesting tidbit I learned on the first day of the conference was about the flag (see below):

2000px-flag_of_tennessee-svg
The Tennessee State Flag, adopted 1905. Image Source: Wikimedia Commons

I bet you were thinking: “Wow, that’s a pretty nice design. But I didn’t come here for pretty pictures–just get onto the vexillology already!” Alright, alright–I’ll move on.

So, there are people who rate flag design (i.e., the North American Vexillological Association), and they don’t play games. For example, here is how they described the new-at-the-time Georgia flag:

“Georgia’s flag [is] ‘a scalawag,’ ‘desolating,’ ‘simply awful,’ ‘hideous’, and ‘by far the ugliest.’ Its complex design violates all the principles of good flag design, incorporating a seal, lettering, and a series of miniature historic flags (in incorrect order).”

For a bunch of people who like flags, they sure burned that one! And not without clout: within two years, Georgia changed their flag.

The Tennessee flag–though it has remained the same since its adoption–is a relatively new flag, adopted in 1905, and it implies what this blog attempts to demonstrate–that our culture, economics, and society are largely shaped by the geology underfoot. The key to the flag is the three stars in the center representing the three “Grand Divisions” of Tennessee: East Tennessee, Middle Tennessee, and West Tennessee. These are geographically (and geologically, see image above) distinct regions that have shaped how Tennessee has come to develop.

The Three Tennessee’s

Tennessee is a long state–about 500 miles long from tip to tip–and it borders more states than any other in the U.S. (Virginia, Kentucky, Missouri, Arkansas, Mississippi, Alabama, Georgia, North Carolina = 8 border states). It’s got a lot of interesting history (the Tennessee Valley Authority could be a whole series of posts in itself), and even more interesting geology…but I don’t have time to get into all of that in this post. Just know that between the incompetent karst, the misty mountains, and the ramblin’ rivers, Tennessee lives up to the scores of songs dedicated to its natural beauty. Since I’m no Tennessee expert, I’m just going to give a brief overview of the three Tennessee’s and some of the history and geology of the regions.

East Tennessee


The Great Smoky Mountains are in the east, a beautiful and biodiverse range shooting off from the Southern Appalachians. Because it is a mountainous region, it has a distinct culture and economy from much of the rest of Tennessee. Plantations never flourished in the ridge-and-valley landscape east of the Tennessee River. As a result, during the Civil War and the formation of the Confederacy, East Tennessee largely opposed the actions of the rest of the state and even attempted to secede from the state to remain in the Union. Though this failed, the East Tennessee Convention did succeed in declaring the action of the state of Tennessee in seceding as unconstitutional (and was heavily occupied by Confederate forces almost immediately as a result).

The very existence of East Tennessee, the conflicts that emerged with the rest of the state, and the unique aspects of American culture it contributes to the melting pot can be  traced back to the Appalachian Orogeny, a series of tectonic collisions that roiled the eastern North American Plate up until about 260,000,000 years ago (at that time, it may be better understood as the central part of the Pangea Supercontinent rather than the eastern part of the North American Plate–though both are true). In a geologic sense, East Tennessee is the most cosmopolitan part of the state, having been formed and influenced by the intercontinental “culture” clashes.

Though the areas of Tennessee are distinct, they are not completely independent of one another.  The mountains of East Tennessee–Himalayan in scale as they were–had a lot of shedding to do before retreating to their relatively squat heights of today. But that sediment did not just disappear. Much of it went East, helping to form one of the largest coastal plains in the world. Some of it traveled west, however, making its way to the Nashville Basin in Middle Tennessee.

Middle Tennessee


The Nashville Basin is, confusingly, a geologic dome that eroded to such an extent that it formed a basin. In fact, it is the southern extension of the Cincinnati Arch. Imagine Mt. St. Helens, but much less dramatic and slowed down several millions of years, with normal erosion substituted for the explosive volcanic force that removed the top half of that mountain. You can get something of an idea of how basins form from arches.

You often don’t see the geology from the surface though. Just because something is in a geologic basin doesn’t necessarily mean the surface is any lower than its surroundings; in the case of Middle Tennessee, it actually is, but not nearly as deep as its subsurface counterpart.

Middle Tennessee is not quite wholly in the stable craton, but it is close. It is like the “beach” that marks the edge of sloshing water. As wave energy (or tectonic energy) comes in, the materials are crunched into themselves, tearing back and forth as it they are pushed by global forces towards the stable land. As the wave energy collides with the stable land, the materials push upward. As these mountains (or surf, as it may be) are pulled down by gravity, their remains sprawl out over the beach, depositing their litter upon an otherwise changeless shore.

This is not a perfect analogy, but the culture and economy of Middle Tennessee are defined by this transitional “beach” status where the orogenies and politics of the East pushed upon the center part of the state. Not quite dominated by plantations, but not mountain culture, the early American development of this region was dependent upon the large rivers that connected it to the established colonies. Fertile soils, underground water (both in aquifers and in caves), rich music, and large personalities are the trademark of this region that was home to Davy Crockett, Andrew Jackson, and countless country music legends and hopefuls.

West Tennessee


West Tennessee is situated contentedly in the stable craton. However, don’t let the continental-scale geology fool you–this region of Tennessee may be the most geologically active. This is the heart of the New Madrid Seismic Zone and the Reelfoot Rift; this is the crown of the Mississippi Embayment (a much larger arch-turned-basin); this is the where the Mississippi River really begins to pick up steam, just south of the confluence of the Ohio.

Mark Twain was a riverboat captain on the Mississippi before he became a celebrated author. In what may be one of his greatest books, Life on the River, he recounts some of the winding stories of the river and the people along it. In Life on the River, Twain rides down the river some 20 years after his piloting career has ended. He describes what it takes to navigate the River, what has changed, what remains, and the lasting stories from the fickle serpent. This excerpt is taken as he approaches Tennessee from the North, near historic “Island No. 10” (near the border of Kentucky/Tennessee/Missouri):

I found the river greatly changed at Island No. 10. The island which I remembered was some three miles long and a quarter of a mile wide, heavily timbered, and lay near the Kentucky shore—within two hundred yards of it, I should say. Now, however, one had to hunt for it with a spy-glass. Nothing was left of it but an insignificant little tuft, and this was no longer near the Kentucky shore; it was clear over against the opposite shore, a mile away. In war times the island had been an important place, for it commanded the situation; and, being heavily fortified, there was no getting by it. It lay between the upper and lower divisions of the Union forces, and kept them separate, until a junction was finally effected across the Missouri neck of land; but the island being itself joined to that neck now, the wide river is without obstruction.

In this region the river passes from Kentucky into Tennessee, back into Missouri, then back into Kentucky, and thence into Tennessee again. So a mile or two of Missouri sticks over into Tennessee.

Also in this region, Kentucky is simultaneously east, west, south, and north of Missouri. You can travel in a straight line west (and slightly south) and go from Tennessee to Kentucky to Missouri to Kentucky to Tennessee to Missouri. It would be a confusing place to live. Fortunately, few people do, for one obvious reason: the River is powerful. As Twain writes about New Madrid (the nearest Missouri town to Island No. 10, and perhaps the most famous town among midwestern geologists):

The town of New Madrid was looking very unwell…It was said that the recent high water had invaded it and damaged its looks. This was surprising news; for in low water the river bank is very high there (fifty feet), and in my day an overflow had always been considered an impossibility. This present flood of 1882 will doubtless be celebrated in the river’s history for several generations before a deluge of like magnitude shall be seen…it broke down the levees in a great many places, on both sides of the river; and in some regions south, when the flood was at its highest, the Mississippi was seventy miles wide! A number of lives were lost, and the destruction of property was fearful. The crops were destroyed, houses washed away, and shelterless men and cattle forced to take refuge on scattering elevations here and there in field and forest, and wait in peril and suffering until the boats put in commission by the national and local governments and by newspaper enterprise could come and rescue them.

West Tennessee is the land of water and cotton, which are twins in terms of the economics of the region. You need water to grow and ship cotton. Cotton remains an important crop in West Tennessee, though not like it was in the past. I happened upon this historic letter-to-the-editor from the New York Times’ archive. Written in 1864 at the height of the Civil War (from even my untrained eye, it looks to be a not-so-subtle form of propaganda), it not only mentions the importance of cotton to West Tennessee but also is emphatic about the delineation between Middle Tennessee and West Tennessee (see! I told you it was important). Even with the South united against the North, Tennesseeans appear to still be entranced by their intra-state differences.

The trip to Tennessee was enlightening, as was the conference. If you are involved in earth sciences or engineering, check out the Environment and Engineering Geophysical Society. They have some great programs, journals, and resources.

And a word of advice: if you are ever in Tennessee, make sure you know your longitude. It apparently makes a difference.



This year was the first time I've gone to the SAGEEP conference. It was as niche as it sounds, but also a really interesting venue to hear the stories of others' research, projects, and novel applications of new and old geophysical techniques. It was a one-stop shop for hearing scientists, engineers, and researchers' using geophysics in agricultural, education, science, dam-building, earthquake characterization, vulcanology and a whole slew of folks using it for marine and land-based military and munitions applications (there is a whole history of geologists in battle situations which I get into in my post Groundwar: Geologists in the Trenches). It was something of near-surface geophysical mecca.

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