Cavern Geology

Cave or Cavern?

Is there a difference between a cave and a cavern? This is a frequently asked question, and many people use the terms interchangeably. However, there is a difference. A cave is any cavity in the ground that is large enough that some portion of it will not receive direct sunlight. There are many types of caves (discussed in this lesson plan). A cavern is a specific type of cave, naturally formed in soluble rock with the ability to grow speleothems. So, although a cavern can accurately be called a cave (since it is a type of cave), all caves cannot be called caverns.

Caves

Caves can be classified into two main categories known as primary and secondary. This classification is based on their origin. Primary caves are developed as the host rock is solidifying. Examples of primary caves include lava tubes and coral caves (descriptions follow). Secondary caves are carved out of the host rock after it has been deposited or consolidated. Most caves fall in the secondary category. However, some primary caves may later be enlarged by the forces associated with secondary cave development.

Smoke Hole Caverns are a system of picturesque caverns in Grant County of West Virginia’s Eastern Panhandle. The caverns were opened to the public in the 1940s. They are located near Smoke Hole Canyon, a gorge, for which the caves take their name. Smoke Hole Caverns are located on WV 28 13 km west of Petersburg.

Some historians claim that Native Americans used the caves for smoking meat, hence the name of the gorge and caverns. The caverns served the same purpose for soldiers during the American Civil War. Folk Lore has it that the cavern was utilized during prohibition by moonshiners. There is only one entrance into the caverns which made it secure and with an ever present supply of fresh water it was a perfect place to produce moonshine. The cavern is also home to an artesian well.

Beginning of Smoke Hole Caverns

The separation of the Americas from the continents of Europe and Africa, or the continental drift, occurred about 600 million years ago. A broad shallow depression from Alabama to Newfoundland was formed. Then, for 400 million years, an ancient sea flooded the area that is now the Appalachian Mountains. Layers of water-borne sediments accumulated on the ocean floor, followed by limestone sediments composed of fossilized marine animals and shells. The weight of the sediments eventually compressed the two layers into metamorphic rock.

As a result of the eons-old shifting of the earth’s tectonic, or crystal, plates, North America and Africa collided. This elevated and fractured the sea floor, causing the older underlying layer of metamorphic rock to tilt upward and slide over the younger layer, creating a towering mountain range, the Appalachians.

Growth of Formations

Most caves result from a simple formula. It consists of a layer of limestone, a mildly acidic mixture of water and carbon dioxide and time – precisely, millions of years. The formation of Smoke Hole Caverns began after the limestone of the Seneca Rocks Area was formed as a result of the inland sea. The enclosing rocks consist of granular crystalline dolomite belonging to the lower part of the Beekmantown dolomite of Early Ordovician age.

The caverns contain no deposits that indicate the former presence of large flowing streams, and most of the cave deposits have been transported and deposited by very small discharges of water. Rain water picks up diluted carbonic acid when it seeps through decaying vegetation in the soil above the rock. The hollowing-out of a limestone cave begins as this acidified water percolated through the fissured limestone dissolving and eroding layers along the way. Water eventually fills all openings enlarging the existing crevices. Run-off soon descends into lower levels of the earth leaving huge limestone chambers.

As the large volumes of water subside and only slow seepage continues, nature’s decorating process begins. Upon entering the unique cave atmosphere, the solution of calcium carbonate gives up some of its carbon dioxide and allows a precipitation of lime to form. This precipitation begins as a thin deposit ring of crystallized calcite. As this process is continued, stalactites form from the ceiling. As the drops fall to the floor, deposits build forming stalagmites. When a stalactite growing down from the ceiling meets a stalagmite growing from the floor, a column or pillar is formed.

Smoke Hole Caverns is an active cave where new deposits accumulate at the rate of one cubic inch in 120 years.

Dripstone

Stalactites are formed often in a fluted and uniformed fashion from the ceiling down. Stalagmites build with distinct mounds and ridges on their way toward the ceiling.

Dripstone, in addition to covering the ceilings and floors, is also abundant on cavern walls. An often more massive decoration is formed when the mineral bearing water spreads over the limestone walls or builds its deposits from a protruding ledge. These crystalline deposits, or flowstone, form draperies and frozen waterfalls, veils and tents.