The Arch!
To log your find, go to the posted coordinates and get a picture of you with your GPS in hand with the bridge in the background. Post the picture (optional) with your log and e-mail me the answers to the following questions.
1. The arch is made from what type of stone?
2. The arch span is approximately how many feet?
3. The arch is how many feet high?
4. How many bridge(s) do you see?
5. How many varieties of fern are located here?
6. The Canadian Hemlocks in the area are said to be dated back to what period?
Any claimed finds without proper documentation will be deleted within 24 hours! You must answer the questions to complete your find. If you don't submit your answers your log will be deleted within 24 hours!
A natural arch or natural bridge is a natural formation (or landform) where a rock arch forms, with a natural passageway through underneath. Most natural arches form as a narrow ridge, walled by cliffs, become narrower from erosion, with a softer rock stratum under the cliff-forming stratum gradually eroding out until the rock shelters thus formed meet underneath the ridge, thus forming the arch. Natural arches commonly form where cliffs are subject to erosion from the sea, rivers or weathering (sub-aerial processes); the processes "find" weaknesses in rocks and work on them, making them bigger until they break through. The choice of "bridge" vs "arch" is somewhat arbitrary. The Natural Arch and Bridge Society identifies a bridge as a subtype of arch that is primarily water-formed. By contrast, the Dictionary of Geological Terms defines a natural bridge as a "natural arch that spans a valley of erosion."
Natural Arch Formation As stated in the definition of what natural arches are, they are formed by the natural, selective removal of rock. The natural processes that lead to selective removal of rock from a rock exposure are almost exclusively processes of erosion. Erosion can selectively remove rock both macroscopically and microscopically. Both modes are effective, albeit on different time scales, because of the basic structure of virtually all types of rock. Rock of any type (with the sole exception of a pure crystal) is a complex matrix of small, interlocking, solid particles. These particles are mostly microscopic fragments of various mineral crystals known as grains. Under high temperatures and pressures, some of the crystalline grains fuse, especially the smaller ones, and act as a cement between the larger grains. Macroscopic erosion occurs when joints or fractures are first induced in this rock matrix through some (usually catastrophic) process, and then widened through a variety of other processes. This splits the rock into distinct macroscopic pieces that can then move relative to each other under the forces of gravity or water pressure. Microscopic erosion occurs when certain processes dissolve the crystalline cement, thus destroying the rock matrix and allowing other processes to disperse the remaining loose grains. Both types of erosion occur separately and in combination on all rock exposures. Only under very special circumstances will a natural arch form. These circumstances include the type, or types, of rock that are present, the shape of the rock exposure (especially in relation to the gravity gradient), and the combination of erosional processes that act upon it. Usually a very specific sequence of erosional processes must operate on a specific shape of rock exposure before a natural arch will form. Since some erosional processes are more effective on certain types of rock than others, the type of rock is also an important factor.
Lateral stream piracy. When two water courses, e.g., two streams, are separated at some point by a relatively thin rock barrier, this barrier may be breached, allowing one of the streams to shorten its path. In a sense, the water of one of the streams is ‘stolen’ by the other. This is known as lateral stream piracy. It can occur in two similar situations. One is at the neck of an incised meander. The other is where two tributaries run closely parallel to each other for a distance upstream of their juncture. The breach in the separating barrier may be caused by any of several processes, but most of these do not lead to arch formation. The process of interest here is wall collapse, which can lead to the formation of a natural arch. The opening created by wall collapse grows down to a level where water can flow through the opening when the stream is in flood. This clears out any debris in the opening and accelerates the growth of the opening. Eventually, the stream channel is re-routed through the opening, completing the process of lateral stream piracy.
Subterranean stream piracy. Water flowing over rock in a channel, e.g., a stream, will, of course, seep into any cracks or joints in that rock. In most cases, seeping water will cause chemical exfoliation and freeze expansion, enlarging the crack or joint. This allows a greater flow of water into the crack or joint which accelerates erosion. When cracks and/or joints combine to create a pathway through the rock through which the water can travel and rejoin the stream (or a different nearby stream), subterranean stream piracy can occur. Basically, the pathway is enlarged until most, if not all the water in the stream flows through it rather than the original channel. It has ‘stolen’ the water from the original stream. When this occurs at the lip of a waterfall, a waterfall natural bridge may form. In other situations, subterranean stream piracy can create long and extensive underground passageways. These may become caverns (a type of natural arch) or, if roof collapse occurs above the passageway, a variety of waterfall natural bridge.
Located in Winston County this natural bridge is the longest rock arch span East of the Rockies! This park is easy to find and is located off Highway 278. Bring your whole family, pack your lunch and have a picnic in the park. There is a hiking trail that will take you through the area. The trial is less than 1 mile round trip. There is a $10.00 entrance fee. Enjoy the cache and the beauty of this natural formation!
The park is open from 8 a.m. to sunset year round 7 days a week!
Sources:
NaturalArches.org
Wikipedia