This is an earth cache and there is no physical container for you to find. To log this cache, please visit the location and message me the answers to the questions listed at the bottom of the page.
Route 128 is listed on many websites as one of the most scenic routes in the USA for geological reasons and it did not disappoint when we visited it. The route has many unique features and this earth cache will bring you to a point where you can see a variety of them and also stretch your legs.
Now face the Colorado River, you may see some kayakers or river rafts on the river. In front of you is an impressive gap that was formed a long time and to the left and right of the gap you see some straight walls next to it with a unique coloring typical for this area.
This earth cache is about the impact of water on the area and how it has impacted every aspect of what you see here.
THE GAP / EROSION
Erosion is the process by which rock material is loosened and then transported away via run off during storms, by streams and by the wind. In many areas on the Colorado Plateau, and particularly in areas with steep slopes, erosion can transport rock fragments away more rapidly than bedrock can be weathered in place, leaving bare rock on the surface. This bare rock forms the cliff faces, domes and slickrock surfaces that dominate the country around Moab.
Roughly 70 and 30 million years ago, through the action of plate tectonics, the whole region was uplifted, resulting in the high and relatively flat Colorado Plateau. Beginning just 5-6 million years ago, the Colorado River began to carve its way downward. Further erosion by tributary streams led to the canyon’s widening around the river.
Research around southeastern Utah and Moab shows this landscape is eroding three or four times faster than the Grand Canyon. The rocks around Moab are measurably weaker. You can mechanically break them or a river can erode through them much more easily.
The Colorado River transitions from the high plateau at the downstream end of the Colorado Plateau, transforming into a cascading waterfall as it descends into lower terrain. This steep zone gradually moves upstream within the river systems due to erosion towards the Moab area causing a higher level of erosion in this area.
THE WALLS / DESERT VARNISH
Desert varnish, also called Patina, thin, dark red to black mineral coating deposited on pebbles and rocks on the surface of desert regions. As dew and soil moisture brought to the surface by capillarity evaporate, their dissolved minerals are deposited on the surface; studies indicate that the varnish materials generally are extracted from the surrounding rock and earth material. Wind abrasion removes the softer salts and polishes the patina to a glossy finish. The rate of varnish formation varies: it generally is thought to take about 2,000 years for it to form in arid areas, because it coats artifacts and natural objects known to be of such antiquity
The sources for desert varnish components come from outside the rock, most likely from atmospheric dust and surface runoff. Streaks of black varnish often occur where water cascades over cliffs. No major varnish characteristics are caused by wind.
Desert varnish often served as canvases for American Indians, who carved petroglyphs onto the shiny surfaces.
The color of rock varnish depends on the relative amounts of manganese and iron in it: manganese-rich varnishes are black; iron-rich varnishes are red or orange; varnishes with similar amounts of manganese and iron are some shade of brown. Varnish surfaces tend to be shiny when the varnish is smooth and rich in manganese.
LOGGING REQUIREMENTS:
1. What is the GC code of this cache?
2. Who are you submitting for (if you are submitting for a group)?
3. Estimate the following:
a) The height of the wall, see reference point, compared to the water level of the Colorado River.
b) The width of the gap, see reference point.
c) The width of the Colorado River at the center of the gap on the day of your visit.
4) What phenomena do you think you may have experienced millions of years ago when looking at the gap?
5) Do you think there is a correlation between the gap and the abundance of the desert varnish at this location? Why or why not?
6) What do you think is the evolutionary purpose of the desert varnish?
7) Why do you think the wall looks so straight and smooth compared to the area underneath the gap?
8) Please post a picture of yourself or your GPS with the river AND the gap in the background in your log.
REFERENCES:
https://www.britannica.com/science/desert-varnish
https://www.nps.gov/articles/desertvarnish.htm
https://www.abdnha.org/TSP-desert-varnish.html
https://spie.org/Publications/Proceedings/Paper/10.1117/12.509695?SSO=1
https://sciencemoab.org/colorado-river/
https://www.moabhappenings.com/Archives/Geology201803MoabAndTheColoradoPlateau.htm
https://moabsunnews.com/2020/10/09/the-edge-of-erosion/ https://www.nps.gov/grca/learn/nature/grca-geology.htm