Ball’s Bluff Battlefield Requiem

Figure 1. A Union artillery piece facing the Balls Bluff battlefield in its approximate position during the battle.

I reported on the geology of this area in a previous post, but I didn’t have much time to explore the area on that outing, so this trip I followed trails all the way around the park. This was the site of a battle early in the American Civil War, October, 1861. The cannon (Fig. 1) is a metaphor of how geology is always in front of us; it isn’t just about really old rocks, but also rivers and beaches, even gas and lava being belched out by volcanoes. That’s all geology too. For example, this battle took place in a field (Fig. 2) .

Figure 2. View from the Union artillery position. It wouldn’t have looked that different in 1861; instead of mowed grass, the field would have been filled with stubble from the recent harvest.

There isn’t much arable land along the Potomac River here because of the rocky soil, but there are a few pockets of land suitable for farming–flood plains left as reminders of the ancient river’s meandering, while it cut its way through rock, gravel, and mud to reach its current position (Fig. 3).

Figure 3. Google Map image of the study area. Our path took us from the end of Ball’s Bluff Road to the southern edge of the map along an inland route. We then followed the bluff (indicated by dark shading) to the north, following the river to the ravine that leads to the Veterans Park trailhead. We cut back to the south, following the gully NNW of the battlefield marker.

The bottoms of the gullies were paved with tilted layers of sandstone and siltstone (Fig. 4), sediment originally deposited in intermontane basins like those that occur in western North America (Fig. 5).

Figure 4. Photo at the bottom of the southernmost valley seen in Fig. 3. Layers of sandstone and siltstone form ledges like this, spaced very hundred yards or so, along the creeks that feed the Potomac river.
Figure 5. Image from the summit of Piestewa Peak in Phoenix, Arizona. The Ball’s Bluff Formation was originally deposited in a similar setting. Sand, silt and clay would have been washed down from local peaks that were probably composed of rocks like the schists comprising the Phoenix Mountains. (Think the Precambrian schists that outcrop along the Potomac River.)

I’d like to finish this post with a thought experiment: Imagine the sediments being carried away from the camera in Fig. 5, passing into the distance to collect in the wide valley that fronts the major fault-block mountain range, seen in the distance; now, imagine everything you see in Fig. 5 being worn down by water and wind and ice, until the sand and silt filling the lowlands in front of the camera is buried beneath the erosional product of Piestewa Peak; imagine that pile of sand and silt and clay being buried many miles beneath the surface, for millions of years.

Can you imagine the rocks seen in Fig. 4?

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: