Have you ever been driving and seen holes in rock walls and wondered what they were?
This earthcache will explain what these exquisite and fascinating holes are.
These geological features are called tafoni. They are deep circular or ellipsoidal rock cavities which vary from tiny pits, softball-sized cavities, and even truck-sized caves! Tafoni usually develop on inclined or vertical surfaces and occur in many different kinds of rocks and many geographical settings around the world.
Tafoni are found in a wide range of rock types such as gneiss, schist, basalt, granodiorite, andesite, eolianite, argillite, porphyry, tuff, conglomerate, lava, and limestone, tafoni are most prevalent on granite, greywacke, and sandstone
It’s not known for sure how tafoni form but it is known they are naturally formed. One theory is they form by moisture, dew or precipitation, which enters these rocks and dissolves some of the harder minerals. These minerals are leached to the surface, where the water evaporates leaving a coating or crust on the parent material. This exposed outer crust then tends to break off because of weather and wind. This is a rock weathering process followed by erosion that begins to eat away at the softer material below and eventually creates the tafoni.
GZ has a safe pullover and is just a small sampling of the area. As you go further south many more tafoni are present in the landscape.
To log this earthcache send us the answers to the following questions:
What type of rock are these tafoni present in at GZ?
What is the size of the largest and smallest cavities that you can see here at GZ?
Do you see a pattern, clusters, lines, pairs, etc., in the distribution of the tafoni? i.e. –If you do why do you think this is?
Do you see other forms of erosion in the area? If so what are they.
Pictures are always appreciated but not required.
References:
Tafoni: http://www.tec.army.mil/research/products/desert_guide/lsmsheet/lstafon.htm
Blackwelder, 1929; Boxerman, 2006; Hejl, 2005; Pestrong, 1988; Smith, 1982
Note: The background image is not from the posted coordinates.
Congrats to bob8bear for grabbing this FTF!