I grew up in Virginia, in the middle of the Blue Ridge Mountains. At 18, when I went off to Minnesota to start college, I had no intention of returning to Virginia except to occasionally visit relatives. Little did I know that, 11 years later, I would be working at a museum less than an hour’s drive from my childhood home.
In spite of my childhood interest in paleontology, I had no opportunities to take a geology class as a child, and almost all my formal geological training took place in Minnesota and Louisiana. As a result, when I returned to Virginia to work for VMNH I found that I knew very little about the geology of my home state. I’ve spent a lot of time over the last decade trying to rectify that deficiency, and I’ve found that as a child I was almost completely ignorant of the range of delightful geologic stories to be found in Virginia. This particular story begins with George Washington.
Long before he was a military officer or politician, George Washington was a surveyor. Prior to the American Revolution he proposed that a canal should be built to provide a water connection between the Atlantic Ocean and the Mississippi River. Washington considered several routes, but preferred a canal that followed the James River and connected it to the Kanawha River, a tributary of the Ohio and, thus, the Mississippi. Washington’s preference for this route was, at least in part, political; a James-Kanawha canal would be located entirely within Virginia (West Virginia was still part of Virginia at that time), while other possible routes would have to be shared with Maryland and Pennsylvania (Ennis, 2006). But there were other advantages to this route of which Washington was almost certainly aware, which I’ll get to in a moment.
In 1785 a company was formed to actually start building the canal (with George Washington as its honorary president), which would begin in Richmond and work its way west. The first stretch of the James River-Kanawha Canal opened in 1790, but building a canal is not a simple endeavor (even with the extensive use of slave labor), and progress was slow. It took 50 years for the canal to reach as far as Lynchburg, and by 1851 it had progressed as far as Buchanan, in Botetourt County (Ennis, 2006). From there the canal was supposed to continue to Eagle Rock, and apparently construction actually began on locks there, but this section was never completed. A combination of Civil War damage and competition with railroads resulted in the rapid demise of the canal. Much of the tow paths (barges on these canals were pulled by mule teams that walked on paths beside the canal) eventually became railroad beds. In more recent years parts of the canal have been resurrected as historical attractions, several miles of the canal have been restored in Richmond:
No remnant of the uncompleted canal or locks remains at Eagle Rock, but across the James River from the town in a well-known (among geologists) roadcut, which is a regular stop for my geology students. The bulk of the roadcut is made up of Silurian and Devonian sandstones that are common in the southern Appalachians. Some of these sandstones have a noticeable yellow, purple, or red color:
The color comes from the presence of abundant iron oxides, especially limonite and hematite. These are among the richest iron concentrations in Virginia, and some of these units contain enough iron to make mining them economically feasible.
There is essentially no iron industry in Virginia today, but at one time Virginia was a major iron producer. According to Gooch (1954), in 1850, the year before the James River-Kanawha Canal reached Buchanan, over 67,000 tons of iron ore were mined in Virginia, producing over 22,000 tons of pig iron. By the end of that century, Virginia was ranked 4th or 5th among all states in iron mining, recovering almost a million tons each year.
Remnants of Virginia’s iron industry are still present, scattered among the iron-bearing Silurian and Devonian rocks. Just a few miles from Eagle Rock the National Forest Service has preserved an iron furnace at Roaring Run (below): another furnace can still be seen on the side of US220 between the towns of Clifton Forge and Iron Gate, just to the north in Allegheny County.
Extracting iron from a rock and turning it into a useful product is not a simple process. The ore must be heated to about 2500 F before the iron melts. Naturally, this requires a large amount of fuel, and for these furnaces the fuel was charcoal from the surrounding forests. A single charcoal furnace at maximum capacity required about one acre of trees per day (Whisonant, 1998); the iron industry denuded the Appalachian forests, and most of the current forests through the Blue Ridge are less than 150 years old.
Iron ores typically contain a lot more than just iron; sulfur is among the other common components. When sulfur is present in refined iron it needs to be removed or the resulting metal will be too brittle to work. This is commonly accomplished by adding lime (CaO) to the furnace. The lime reacts with the sulfur, removing it from the melt and leaving the iron more pure. So the furnace was filled from the top with alternating layers of charcoal, iron ore, and lime, and air was pumped in from the bottom of the furnace to provide oxygen to the fire. The air was usually pumped in by bellows that were powered by water wheels, so the furnaces were often located next to streams (as was the case with both Roaring Run and Clifton Forge) (Whisonant, 1998).
So furnaces like Roaring Run were located in the iron-rich sandstones, near streams that could provide power for bellows and in forests that could provide fuel for fires. Lime is a different matter. The usual means of obtaining lime is by heating carbonate rocks such as limestone. Unfortunately, the Silurian and Devonian rocks in Virginia are poor in carbonates; the most common Virginia carbonates are from the Cambrian. Looking at a geologic map of the area, it’s clear that for furnaces in the Roaring Run and Clifton Forge area, the closest Cambrian carbonates are a few hundred yards south of Eagle Rock (data drawn from USGS and GoogleEarth):
Traveling south on US220, within a matter of meters after crossing the Cambrian-Ordovician boundary an abandoned limestone quarry is hidden in the woods beside the road (the quarry is inaccessible, but it’s visible on GoogleEarth):
These are lime kilns, furnaces for heating limestone to produce lime. The lime from these kilns was used for many purposes (in fact, these kilns were still operational into the 1950’s, long after the iron furnaces were shut down), but almost certainly one of their original primary uses was to supply lime for the iron industry.
That leaves only one more issue for the Botetourt-Allegheny iron industry. For all the iron production in the area, this was not a major population center in the 1800’s (or even today). How do you move the iron and lime (which had other industrial uses) to the city? Prior to railroads, you needed to use either a wagon or a canal boat to transport it to Richmond. I think the other reason George Washington wanted the canal to follow the James River was because it would run through the heart of Virginia’s iron region.
Even though the canal never made it to Eagle Rock, it did eventually reach Buchanan, about 20 miles away. It seems that at fair amount of iron was being transported along the canal, because along the canal in Richmond we find this structure:
This is part of Tredegar Iron Works, which up until the end of the Civil War was one of the largest iron manufacturing centers in North America. During the war almost all the Confederacy’s iron equipment, from musket balls to the armor plating of the CSS Virginia, was produced by Tredegar, using iron mined from the Virginia Appalachians.
Tredegar was largely destroyed during the war, as were many of the Confederacy’s iron furnaces; the James River-Kanawha Canal was also damaged. Technological progress and exploration did the rest. Railroads, often laid directly on the old canal tow paths, finished off the canals, while iron mining moved to areas like southwestern Virginia that had easy access to coal (which made smelting much more efficient), and later to areas with higher-grade ores such as the Proterozoic banded iron formations in Minnesota and Michigan. With the Appalachian furnaces shut down the forests began to regrow and, other than the rocks themselves, most of the components of Virginia’s once-thriving iron industry have either fallen into disrepair or entirely vanished.