This EarthCache will highlight the Natural Bridge, considered one of the "great natural wonders of the world," and three other features along the Cedar Creek Trail. These other stops will be the Saltpetre Cave, the Lost River, and Lace Falls. All of these features can be seen along the round-trip 1.75 mile Cedar Creek Trail.
Natural Bridge is located in Virginia's Shenandoah Valley in the Southern Appalachians.
The first stop along the way will be the Natural Bridge itself. This feature and the surrounding acreage was surveyed in 1750 by George Washington whose initials can still be seen today carved in the wall across Cedar Creek. Development of the area began in 1774 when Thomas Jefferson purchased the Natural Bridge and 157 surrounding acres from King George III. Two years into his term as President of the United States, in 1803, he constructed a small log cabin on the grounds for guests. It remained in his estate until 1833 when sold by his heirs.
The Natural Bridge is exactly what it sounds like - an arch of calcareous rock spanning the canyon above Cedar Creek. It served as a bridge for travelers both on foot and horseback when owned by Jefferson and still performs the same function today as the route of U.S. Highway 11.
Many geologists believe that the Natural Bridge was formed when the waters of Cedar Creek were diverted into a cave. The stream flowed through a natural tunnel, for a distance of several miles, before once again emerging above ground. Eventually the roof of the tunnel collapsed leaving Cedar Creek flowing through a canyon. The surviving bridge remains as the last stable part of the former tunnel roof.
Both before and after the tunnel you will notice that the layers of rock are inclined rather than flat lying. The fractures in these layers are a result of the uplifting of the Appalachian Mountains about 200 million years ago. Many of the breaks have been forced open by the freezing and thawing of water over the years. These fractures and the inclined angle of these layers are likely responsible for the collapse of this portion of the tunnel. Once under the bridge you will then notice that the layers of rock seen here are flat lying. The layers are inclined toward the bridge, both upstream and downstream because the location of the bridge is the axis, or center, of a downward fold in the strata known as a syncline. This is likely the only reason the bridge remains standing today.
The next stop along the trail is the Saltpetre Cave. During both the Civil war and the war of 1812, earth from this cave was mined and the nitrates formed in it from bat droppings were used to make gunpowder. The Saltpetre cave was formed mainly by stream erosion. Located on the outside of a curve in Cedar Creek, this area was undercut by the stream in periods of high water. Parts of the roof have since collapsed and the stream water has dissolved and smoothed the ceiling.
The next stop is the Lost River. This is a hole blasted open by the workers of the Saltpetre Cave in 1812 after hearing water behind the solid rock wall. From the opening you can here the stream flowing over cascade or waterfall a short distance under the ledge. Many attempts have been made to locate either the source of destination of this underground stream but none were ever successful.
Finally you will reach the end of the trail near Lace Falls. Just before the falls you will notice the creek flowing over many small cascades caused by the upturned layers of rock from the syncline. Lace falls is a result of those beds becoming more steeply inclined. The water flows over the edge of the upturned layers creating a waterfall. Lace falls can be either delicate veils of water or rushing plumes of white water depending on the season.
The Natural Bridge and Cedar Creek Trail are operated as a commercial attraction and require a fee for entrance. You may choose to take a series of steps to the bottom of the Cedar Creek canyon or a shuttle bus. The Natural Bridge is open every day. While it is possible to go at night, I will need to see what I have asked for in the pictures in order to receive credit, so daylight is best.
To claim this as a find:
1. How much (in US dollars) did Thomas Jefferson pay for the Natural Bridge and 157 surrounding acres?
2. What type of rock makes up the arch?
3. About how many pounds would the rock span weight?
4. How high is the top of the arch above the canyon floor?
5. How many bushels of "soak" and how many bushels of elm ash did it take to make 100 pounds of saltpetre? (Optional since the sign is missing. Can still be answered.)
6. What was used to try and locate the source and destination of the Lost River?
7. How far away are the headwaters of Cedar Creek?
8. How far does Cedar Creek drop at Lace Falls?
9. Take a photo of yourself and your GPS with the Natural Bridge in the background. (Optional)
10. Take a photo of yourself and your GPS with Lace Falls in the background. (Optional)
E-mail the answers (numbers 1-8) that you can find within a few days of your log.
Failure to comply with these requirements will result in log deletion.
Good luck and good caching.
- Rev Mike