Day 6:  Natural Bridge & Caverns

Location:  Natural Bridge & Caverns is located in the Valley and Ridge province just outside of Lexington, Virginia.  From Blacksburg, we will take I-81 N to Route 11 (between exits 175-180).  This is about a 1.5 hour trip.

Equipment:  Walking shoes, notebooks, pencil, and camera.

Schedule:
8:00        Meet in hotel conference room in Blacksburg and discuss day's itinerary.
8:30        Check out of hotel and load vans.
9:00        Depart from Blacksburg, VA and head to Natural Bridge.
10:30      Arrive at Natural Bridge.  Admire nature's work, walk the nature trail (1 mile), and visit Monacan Village.
12:00      Eat lunch at Summerhouse Cafe.  (This is creek side and offers sandwiches.)
1:00        Explore the caverns.
3:00        Depart from Natural Bridge and head for Richmond hotel (where we will stay for the night).

Natural Bridge:
Natural Bridge is said to be one of the Seven Natural Wonders of the World.  As interesting as its existence is its history.  George Washington's initials remain on the wall of the bridge from when he surveyed the site in 1750.  In 1774, the bridge and surrounding 157 acres was purchased by Thomas Jefferson  from King George III for 20 shillings.  Since then, the bridge has remained privately owned.  However, the bridge attained resort status in the 1880's under the ownership of Colonel Henry Parsons. Natural Bridge has remained a vacation spot for intrigued guests around the world since this time . (Natural Bridge of Virginia, 2002)

Natural Bridge belongs to the karst topography typical of the Valley and Ridge province of Virginia.  The rock forming the bridge is a dolomite bearing limestone of upper Cambrian age.  Although some are still skeptical, most geologists believe that most of the cave roof  collapsed to leave only the part that is now the bridge.  Therefore, the bridge is a result of the limestone being chemically weathered.  The dimensions of the bridge are as follows:  height of lower surface of arch above Cedar Creek is 160 feet; width is 150 feet; thickness of rock span is 37-50 feet; and intrados of arch is 150 feet (Dietrich, 1970).

Cedar Creek Nature Trial:  This mile long trial begins along Cedar creek and ends at Lace Falls.  Along the beautifully scenic walk, you will see Saltpeter cave, The Lost River, and a small waterfall known as Lace Falls (Natural Bridge of Virginia, 2002).

The trial begins here at Cedar Creek:

Along the way you come to Saltpeter Cave, which was mined for nitrates to make gunpowder during the civil war:

Next, you will come upon the Lost River.  You will see its waters flow from an unseen cavern above to one below the creek.  It is visible through an arch in the side of the mountain:

Finally, the nature trial ends with a view of Lace Falls.  The waterfall is that of a small, but beautiful 50 foot drop:

Monacan Village:  At Monacan Village you will experience life 300 years ago in a typical Monacan Village.  You will learn about activities of the past including canoe building, gardening, fishing, etc.  Below is a picture taken at lunchtime in Monacan Village (Natural Bridge of Virginia, 2002):

The Caverns:  Caverns are underground "openings" or chambers typically formed from the chemical weathering of limestone (Tarbuck, 1999).  Limestone is a dominant rock type within the Valley and Ridge province and thus is part of the bedrock in the Natural Bridge area.  The caverns here formed as carbonic acid "ate away" at the limestone rock.  Carbonic acid is formed as carbon dioxide from the air mixes with water (from precipitation).  This weak acid then leaches into the ground, contacts the limestone, and begins to dissolve it.  After many years, caverns such as those at Natural Bridge result.  The icicle-like calcite deposits that form as the limestone is dissolved and hang from the roof of a cavern are called stalactites.  The calcite deposits that build up from the cave floor are called stalagmites.

Here is a good  picture of stalactites and stalagmites (Bewley, 1995).

Below are pictures of the Natural Bridge Caverns (Natural Bridge of Virginia, 2002):

After a day at Natural Bridge and Caverns, you should have an understanding of karst topography.  You should enjoy the beauty nature has offered as well as appreciate the science that explains these vast and mysterious structures.