Tafoni at Falls Mill EarthCache
-
Difficulty:
-
-
Terrain:
-
Size: 
(not chosen)
Please note Use of geocaching.com services is subject to the terms and conditions
in our disclaimer.
This cache is located near U.S. 19 in Falls Mill, Braxton County, West Virginia. After turning onto Pleasant Hill Rd. from U.S. 19, enter a public recreation area with a ball field, public parking and seasonal restrooms. The cache site is next to a walkway and easily accessible.
“Tafoni are ellipsoidal, pan- to bowl-shaped, natural rock cavities. These cavernous weathering features include tiny pits, softball-sized cavities, truck-sized caves, and nested and cellular honeycomb forms. Tafoni typically develop on inclined or vertical surfaces and occur in groups. These exquisite and fascinating cavernous weathering landforms are present on the surfaces of many different kinds of rocks located in a multitude of geographic regions around the world” (Boxerman, Tafoni.com).
Tafoni are unique geological phenomena. Such geological formation is commonly known as honeycomb weathering. Differential weathering of sedimentary rock, with cementing that is weak in some places and strong in others, leads to a honeycomb-like effect (McDowell).
Here is one explanation of how these kinds of pockets may have formed: Rain water soaked deep into sandstone and mixed with existing calcium. During the dry season, the water evaporated from the stone, carrying some of the dissolved calcium to the surface of the stone. This evaporation process caused any calcium remaining in the interior of the stone to be distributed unevenly so that there were some soft, low-calcium areas and some hard, high-calcium areas.
Later in time, if the outer surface of the sandstone is cracked or broken, the softer parts of the interior erode away more quickly than the harder areas, creating tafoni formations.
This type of weathering is not completely understood and geologists are not unanimous in their opinions. Because different weathering processes are involved and the results are many different sizes and shapes of pockets, it is not understood how tafoni start or what controls the size or shape of the cavities. The time span may be 100 years or 1,000,000 years.
Geologists do know that tafoni occur all over the world, both in saltwater tidal areas and on continents far from the sea, most commonly in granite or sandstone. The tafoni at Falls Mill are a beautiful example of this unique geological formation in sandstone.
In the same recreation site as this Earthcache are the falls of the Little Kanawha River. These falls form the northern end of Burnsville Lake. The falls, the cache location and the surrounding area lie within the Burnsville Lake WMA and are open to the public year round. Also available near the falls are picnic tables, an observation platform for viewing the falls, fishing, and a walking trail.
To receive credit for this Earthcache, e-mail us the answers to
Question #1: Estimate how far in feet the tafoni lie above the falls.
Question #2: How do you think these particular tafoni were formed? What weathering agent uncovered the outer surface of the sandstone and shaped these formations?
Additional Hints
(No hints available.)