Natural Bridge
It's a long trip from the GMU Fairfax Campus to Southwestern Virginia, so we'll stop on the way to get "grounded" in geology.
Natural Bridge is, first of all... natural. It was created when rainwater hit the ground, then became slightly acidic as it absorbs carbon dioxide as it seeped through the biologically-rich layer of soil. That carbonic acid (H2CO3) dissolved limestone (CaCO3) bedrock, carrying the calcium carbonate away in solution. In the process, cracks in the bedrock expanded to create an underground hole, forming a cave.
The cave grew along a crack, forming a tunnel with a rock roof. Further south near the Tenneessee border, there is a Natural Tunnel State Park - with a tunnel so large, a train track runs through it.
Ultimately, enough rock dissolved and the roof started to collapse. What we see today as a natural bridge is the last remnant of the roof, the part of the cave that has not collapsed yet.
The rainwater that seeped underground and etched the cave came back to the surface at a spring, and has formed Cedar Creek. Cedar Creek drains into the James River, ultimately flowing into the Chespeake Bay at Norfolk and then the Atlantic Oceean. But what happened to the rock that dissolved in the acid groundwater?
Some came out of solution, when the groundwater reached the surface and the carbonic acid released carbon dioxide into the atmosphere. In the chemical reaction, the calcium ions rejoin with the carbonate ions and precipitate, often in the form of the mineral travertine. At Natural Bridge, you can see travertine in the stream paralleling the steps from the visitor center/gift shop down into the valley of Cedar Creek. In caves, you can see the redeposited calcium, as the minerals calcite or aragonite, in cave formations or "speleothems" - stalactites, stalgmites, etc.
Most of the dissolved calcium carbonate dissolved underground at Natural Bridge was carried by Cedar Creek downstream to the James River. Ultimately, it reached the Chesapeake Bay and the Atlantic Ocean. There, the calcium dissolved in the water may have been absorbed by zooplankton (such as foraminifera) and incorporated into a microscopic shell - or even into a clam/oyster shell. When the animal died, the shell settled on the ocean floor and was incorporated into future limestone bedrock, or perhaps will end up as calcite veins in basalt bedrock. In the process, carbon was sequestered in the shell, and was removed from the atmosphere.
Natural Bridge has been private property since Thomas Jefferson bought it in 1774 from the colonial government in Williamsburg. Jefferson, an early American scientist, may have considered the site more than just a tourist attraction. He sought to counter European claims that America was a degraded environment by highlighting how America was "better" - animals were bigger, climate was sunnier, etc.
Natural Bridge, like Luray Caverens, is not a state or national park. It is a private, commercial tourist site. Unlike Mount Vernon and Monticello, Luray Caverns is a for-profit operation.
Re-creation of Monacan Town
| Since 2000, the Monacan Tribe has re-created an interpretive village at Natural Bridge. This was done in partnership with the commercial owners of the tourist site, who are trying to offer more attractions. For the tribe, the site offers an excellent opportunity to educate far more people about Monacan culture and heritage, beyopnd the small number of people who visit the Monacan Ancestral Museum in the Blue Ridge.
The building materials and construction techniques in the village reflect the technology and culture of the 1700's, except the reeds are not the local cane that would have been used 300 years ago. That cane is rare, due to overgrazing. The phragmites reeds used in most Indian village recreations is a non-native invasive species that is overwhelming natural marshes in the Chesapeake Bay.
The authenticity of the re-creation is affected by the location in the valley of Cedar Creek at Natural Bridge. The number of dwellings, the distance between structures, the size of the garden, and even the garbage midden are affected by the constraints of being a tourist atraction. At a modern tourist site, do you think you'll see a re-creation of how Monacans extracted sinews from a deer carcass, or experience the flies and other insects that must have been associated with human settlements?
And do you think any tribe would have built a village in such a valley? The pallisade of sticks and woven branches surrounding the village was major investment in security infrastructure, to deter attackers from racing directly into the village. (No, even before European settlement in North America, everyone did not live in peace and harmony.)
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ati (recreated Monacan dwelling) at Natural Bridge |
Today, reenactors and others debate whether a wall around the village would have included the horizontal branches woven to make a tight barricade. Village walls may have been just a loose fence of vertical logs with no horizontal branches, slowing an attack but allowing residents to escape by slipping through the gaps. Archeological evidence does not tell us; the postholes preserved in the soil do not document the design of the wall above the posts.
No matter how the wall was built, village leaders would have been conscious about locating the village in an easy-to-defend place. Putting a village in a dead-end narrow valley under Natural Bridge, where enemies could easily fire arrows and throw rocks from above, would have been foolish 300 years ago - but may be a brilliant outreach and marketing decision today.
Questions to consider:
- - Why did tourists first go to Natural Bridge? Why doesn't everyone in the world go now?
- - What are the seven most magnificent natural wonders you have seen in your life so far? What's on the list to see before you die?
- - What evidence justifies a claim that George Washington surveyed a tract of land including Natural Bridge, or carved his initials on the bridge?
- - Do you think Lost River is really "lost"?
- - Would Natural Bridge be less interesting, or attract fewer tourists, if the reference to Washington was revised?
- - If a rock falls off Natural Bridge and hits a tourist on the head, or a hornet stings a visitor... should there be a lawsuit?
- - Is Cedar Creek "pristine"? How far has it travelled, and through what sort of landscape, before arriving at Natural Bridge? What is the greatest threat to water quality of Cedar Creek?
- - Why are there ledges in Cedar Creek? Are they different from the ledges in the New River?
- - How would tourists at Saltpeter Cave affect the bats that produced the guano used to make gunpowder in the Civil War?
- - How does Natural Bridge keep tourists out of Cedar Creek? What sort of materials were used to surface the walking trail?
- - Should the native vegetation be protected from the native wildlife?
- - How much should the natural setting be modified for interpretation?
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recreated teepee at Mountain Lake - where Native Americans would have built a very different structure from bark and reeds, not a teepee
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For more background, read:
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bark-covered lodge recreated at Explore Park near Roanoke
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Links/Resources
Virginia From the Ground Up - Southwestern Virginia
