Earthcaches have no "box" to find. Rather, with this earthcache, you discover something about geology. For more information, see earthcache.org.
Overview
Welcome to beautiful Oakwood Cemetery, a place of peace and rest for thousands of citizens for more than 140 years. Oakwood Cemetery is the final resting spot of seven governors, five United States Senators, eight Supreme Court Chief Justices of North Carolina, four Civil War generals, two Secretaries of the United States Navy, numerous Raleigh mayors, and thousands of other individuals.
Have you ever visited a cemetery and tried to read the name on a headstone and could not? You can't because of a process called weathering. "Weathering is defined as the breakdown of rock in situ, that is, without being moved."
Weathering is often confused with erosion, but the word erosion implies that the rock has been subjected to transport processes which has worn it down
Weathering
Weathering falls into three categories: physical, chemical, and biological. It is common to see more than one type of process on a grave stone.
Physical Weathering
Physical weathering is caused by the effects of changing temperatures on rocks, causing the rock to break apart. The process is sometimes assisted by water.
Chemical Weathering
Chemical weathering occurs when water, air, and other substances react with the mineral grains in rocks. In chemical weathering, the composition of the rock changes. These reactions occur particularly when the water is slightly acidic.
Biological Weathering
Living organisms contribute to mechanical weathering through the growth of roots or the burrowing of animals.
Lettering Weathering
A useful assessment of the sharpness of engraved letters called Rahn’s Index. This index suggests that the alteration of carved lettering on headstones follows a sequence of deterioration with the lettering becoming progressively roughened and difficult to read. The edges of the carved surface at first become less distinct as granular disintegration occurs. The whole letter begins to merge into the surface of the headstone as weathering occurs. Eventually the lettering becomes almost indistinguishable from the surface of the headstone itself. Once the lettering is indistinguishable, the index becomes inappropriate to use. This index does not provide any absolute measurements of the amount of material lost, but it can provide a relative measure of deterioration.
Rahn’s Index
|
Visual Weathering Class
|
Visual Indicators of Class
|
|
1
|
Lettering is sharp and distinct. There is no evidence of change.
|
|
2
|
Lettering is slightly rounded. It shows evidence of some removal of grains. Lettering is still legible and clear.
|
|
3
|
Lettering is rounded. The edges are clearly being removed and some original edges have been removed completely. Lettering is still legible and clear.
|
|
4
|
Lettering is rounded. All or most of the original edges have been removed, but the lettering still legible, but it is increasingly becoming indistinct from the surface of the gravestone.
|
|
5
|
Lettering is disintegrating. Lettering is still just about legible, but it now is almost indistinguishable from the surface of the gravestone.
|
|
6
|
What lettering? Lettering has virtually disappeared.
|
Logging Tasks: (Required)
Please send you answers via geocaching message center (preferred) or email.
- Evaluate each of the following stones and tell me the following:
- What type of weathering is present here? Give some descriptions of what you are seeing.
- How you would rate each headstone based on Rahn’s Index. What visual indicators made you determine each choice? Use your best educated guess on these. Deterioration has a degree of judgement.
- Stage 1: Tarlton, "The Rubicon" N35 47.261 W078 37.542
- Stage 2: Barber N35 47.204 W078 37.656
- Stage 3: Ouida Hood Prikryl N35 47.215 W078 37.620
- Stage 4: Etta Ratliffe N35 47.249 W078 37.697
- Stage 5: Anneliese McCain N35 47.207 W078 37.441
- Please post in your "Found it" log a picture of you, your GPS, your group, an arm, your geo-pet -- at one of the 5 gravestones used in this Earthcache.
References