Field-Trip #3c: Natural Chimneys

After spending the morning at the local Produce Auction and carefully choosing the perfect pumpkin from a local farmer's pumpkin patch, we headed to the Natural Chimneys.  

 

It's hard to imagine, but the Shenandoah Valley (part of Virginia) was once the floor of a great inland sea. Centuries ago, as that sea receded, the forces of nature carefully etched out an awe-inspiring formation of solid rock. The seven Natural Chimneys tower as much as 120 feet above the pastoral terrain of the Shenandoah Valley.  

Mac, Natural Chimneys

  

Izzie, Natural Chimneys

Izzie and Mac, Natural Chimneys 2012

Though they closely resemble a medieval castle, the term “natural chimneys” is the one most commonly used today. This reference to chimneys can be traced back to the early history of this section of the Shenandoah Valley. The region’s earliest settlers, mostly from Pennsylvania, constructed massive chimney-like structures in which to heat or burn the local limestone for use in agricultural endeavors. After the discovery of iron ore, smelting furnaces, or “chimneys” were built to extract the iron. Prior to the civil war, significant quantities of iron were produced in this area. At this time, the easily accessed ore deposits were exhausted and the men who worked the ore and furnaces left to fight for the Confederacy.  Although named for man-made structures, the chimneys were created entirely by nature.

 

Having been completely submerged by a vast, but shallow inland sea, the chimneys themselves are made up of numerous layers of compacted sediment. Within some of these layers, the fossilized remains of the sea creatures that once thrived here can be found. Equally as important to the formation, and perhaps more important to the preservation of the chimneys were the sponges that inhabited this area. As the sponges grew they secreted a silicone like substance which solidified to form a type of stone that is considerably harder than the sedimentary rock in which it is found. This material is referred to as chert. 

Exploring and learning about the different components that make up "chert".

The layers of the stone vary in both thickness and color due to the fact that as the temperature of the sea water fluctuated, so did the types and quantities of the marine life within the sea. The darker stone that caps the columns is chert, and since it is much harder than some of the layers beneath, it serves as a protective roof over the formations. Additionally, the chimneys contain a volcanic layer. Originating at a point about ten miles north of the chimneys, volcanic activity was so powerful that it was able to squeeze a layer of lava between two layers of limestone. Throughout the years, water also came into play in turning the chimneys into what they are today. When water flowed through this area, it deposited minerals such as calcium and iron which seeped down into the stone and further hardened it. Through the course of time the chert caps have played a vital role in preserving the chimneys.

Exploring the area around the chimneys.  

We had an amazing day full of field-trips!  We were completely exhausted, but had such a great day exploring the Shenandoah Valley!