-
Difficulty:
-
-
Terrain:
-
Size: 
(not chosen)
Please note Use of geocaching.com services is subject to the terms and conditions
in our disclaimer.
Congratulations to srladybug as FTL (first to log)!
This Earthcache is within the White Tank Mountain Regional Park. An entrance fee will be required. There will be no reason to leave the designated trail, so please stay on it. As always, obey all of the Park rules and regulations.
Parking is at N33 35.385, W112 30.450. From here follow the Waterfall Trail to the Earthcache. The trail is paved for part of the way and is a fairly easy walk. Remember, however, that this is a desert hike and come prepared. Bring water and well constructed shoes. Most of the vegetation has either thorns or needles and should not be handled. Never place your hand where you cannot see it, as poisonous snakes, scorpions, and other dangerous animals are found here.
The granite rock found in this part of the mountains is white when a fresh break is exposed. However, looking around, most of the rock is colored from dark brown to dark mahogany. A closer look reveals that the exposed rocks are all coated with a thin, dark, shiny coating. This coating is known as ‘desert varnish’.
Much of the Park is composed of the rugged White Tank Mountains. The White Tanks are named for the natural water pools found in shaded canyons. The rims of these natural tanks have had the dark patina of ‘desert varnish’ removed by the scouring action of flash floods, exposing the white granite underneath. These white rims give the mountain range its name. A good example of this can be found at a nearby Earthcache, GC242ZE – A Tank In The Park.
The desert varnish is composed of manganese, iron, and clays on the surface of sun-baked boulders. Currently, desert varnish is believed to form from clay dust deposited on sun baked rock surfaces and then acted on over many years by bacteria. The bacteria live on the clay dust and absorb manganese and iron from minute particles in the air. Over time, the combination of the clay and the bacteria form the desert varnish. Varnish bacteria thrive on smooth rock surfaces in arid climates. These desert varnish coatings are very thin, being less than 8 thousandths of an inch. That’s less than two sheets of paper! According to some scientists, perhaps 10,000 years are required for a complete varnish coating to form in the deserts of the southwestern United States. In fact, dating of varnished surfaces is of enormous importance to the study of desert landforms and also in dating of archeological sites.
Another place where the difference between the desert varnish and the underlying white granite is noticeable is the numerous petroglyphs, which can be found along this trail. The Hohokam and earlier Indians took advantage of the startling contrast between the white granite rock and the dark desert varnish coating. Painstakingly, they removed the desert varnish to form geometric and natural shapes known as petroglyphs.
The main location of the Earthcache is known as Petroglyph Plaza. Figures of people, animals, and geometric shapes can all be found. Estimates of the relative ages of the various petroglyphs can be made by comparing the amount of the desert varnish that has formed in the lines of the individual petroglyphs. Using these observations and information about the rate at which the desert varnish forms, some of these petroglyphs are estimated to be on the order of 10,000 years old. Another good example of the petroglyphs can be found a little further down the trail at N33 35.110, W112 31.122.
Important notice from the Park: “Please do not try to make "tombstone rubbings" of the petroglyphs. It doesn’t work at all and you will erode the dark areas, making the petroglyph dimmer. Look at and photograph these figures and symbols of history, but please don’t touch the petroglyphs, skin oils can also damage them.”
Please take and post a picture of yourself at ground zero. Note, this is optional but encouraged.
In order to log this Earthcache, you will need to do the following:
1) Email the answers to 2) and 3) to the cache owner.
2) Examine the petroglyphs here and further along the trail. Remember, do not touch! Can you see a difference in the ‘whiteness’ of the lines between some of the individual petroglyphs? Since the underlying rock is the same color, what could be causing the difference?
3) Go to www.wunderground.com/history/airport/KLUF and record the minimum and maximum temperatures on the day of your visit. Email the cache owner and post in your log.
Additional Hints
(No hints available.)