Green River Formations Earthcache
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As an earthcache, there is no “box” or “container” to discover. Rather, with this cache, you discover something about the geology of the area. For more info, consult www.earthcache.org
For paperless cachers, the logging requirements are at the beginning of the description.
Getting There:
This earthcache is located just off the Green River / Flaming Gorge Range Way exit. It is accessible from either direction. The cords lead you to a local business' parking lot. There are also several wide shoulders (during non-snow seasons) that allow you to look UP at the formation.
There are four formations that are part of the Green River Formation that are easily visible from this parking lot: The Towers, Teakettle Rock, Sugar Bowl Rock, Giants Thumb. Attempt to figure out which one is which (its kind of like finding shapes in the clouds) for one of the logging requirements.
Logging Requirements:
Send the answers to #1-#5 to me through my geocaching profile. DO NOT post the answers to any logging requirements on this site.
1. List the name “GC2JPGQ Green River Formations Earthcache” in the first line of your email. Also, list the number of people in your group.
2. Viewing the formations:
A) Look up at the formation towering behind the village – from LEFT to RIGHT, list them in order (Sugar Bowl Rock, Giants Thumb, Teakettle Rock, The Towers).
B) Which of them appears “biggest” from your vantage point?
3. Geological Identification:
A) Based on the reading in this description, which LAYERS of the Green river Formation are visible from this point?
B) Describe the dominate color of the formations. Based on the descriptions of GRAIN SIZE described below, why has part of the formation eroded into such spectacular shapes while other parts have not been eroded very much?
4. (optional requirement based on GC.com guidelines, but it sure helps verify your smiley if your answers to the above are not “quite right”) Post a picture of yourself and/or your GPS with your log that shows You with the LODGING BUSINESS in the background behind you. Please don't show the formations in this picture since it would give away the answers to logging requirements!
I will only respond if you have incomplete logging requirements. Go ahead and log your cache
Geology:
"Eocene time is most noted for the accumulation of oil shale beds in southwest Wyoming and adjacent parts of Utah and Colorado. These organic-rich shales, called the Green River Formation, accumulated in large, shallow, playa lakes called Lake Gosiute and Lake Uinta. Countless fish skeletons, delicately preserved..., can be seen at Fossil Butte National Monument west of Kemmerer, Wyoming." “The Green River formation can be tought of as a giant lens of lake sediments surrounded by stream sediments of the Wasatch formation.” The sediments were deposited in very fine layers, a dark layer during the growing season and a light-hue inorganic layer in winter. Each pair of layers is called a varve and represents one year. Many scientists believe that the sediments of the Green River Formation present a continuous record of six million years. On any account, the average “varve” is about .18 mm thick, though some are as thick as 9.8 mm. As you look at the layers, you simply see what looks like a “texture” of light and dark. Aren't you glad that COUNTING the layers isn't one of the logging requirements!?
Beginning west of the GZ (west of the Interstate's intersection with US Hwy 191), you can see both greenish-brown sandstones and dark brown (and blackish) oil shales throughout the area. These all belong to the flat lying Eocene Green River formation. At the town of Green River, there are twin tunnels that have been cut through this formation. Also in the are is the famous Castle Rock as well as Palisades (that these formations are considered a part of). In some areas you can see a white layer sandstone layer, usually lower down in the formation. Other layers are much finer in nature, made of siltstone and usually darker. It is important to remember that the Green River formation is composed of hundreds of layers of sediment and thus it varies vastly in what it is composed of from “top to bottom”!
Terms:
Sandstone:
Sandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains. Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any color, but the most common colors are tan, brown, yellow, red, gray and pink, white.
Siltstone:
Siltstone is a sedimentary rock which has a grain size in the silt range, finer than sandstone and coarser than claystones.
As its name implies, it is primarily composed (greater than 2/3) of silt sized particles, defined as grains between 3.9 and 62.5 micrometres Siltstones differ significantly from sandstones due to their smaller pores and higher propensity for containing a significant amount of clay. Although often mistaken as a shale, siltstone lacks the structure (fissility and laminations) which are typical of shale. Unless the siltstone is fairly shaly, stratification is likely to be obscure and it tends to weather at oblique angles unrelated to bedding. Shale are rocks that contain mud, which is material that has a range of silt and clay. Siltstone is differentiated by having a majority silt, not clay.
Oil Shales: There are several different types of Oil shales and the mineral and chemical composition of oil shales varies by region. In summary, oil shales are sedimentary rocks (fine grained, similar to silt stone) that contain organic oil-rich compounds that could be/can be extracted as oil. They are not the same as the Petroleum rich sands common to Saudi Arabia and Alaska but with techonology oil can often be extracted. Oil is extracted through pyrolysis (heating of the rock) until the oil turns into a vapor and then is redistilled. The formation here is considered a siliceous shale since it contains significant silicate minerals (such as quartz) and merges/overlaps with the silicate sandstone so visible in the Green River formation.
Eocene time: This is the time period geologically that first has mammal fossils present within the formation. The end of the Eocene layers contain the distinct and abrupt extinction event which terminated the “age of the dinosaurs.” Some geologists place these geological period from 56 to 34 million years ago, while other would consider this the geological time period immediately preceding the biblical/historical “worldwide flood” event.
History/Extraneous Information:
The town of Green River was a Pony Express and stage station. Later, when the Union Pacific Railroad came to the area, it became a major stopping place for travelers. The first geologist to do extensive work in the area was John Wesley Powell 1869. Powell's exploration party is most know for their explorations of the Grand Canyon (Lake Powell).
Resources:
Lageson, david R. and Darwin R. Spearing. Roadside Geology of Wyoming. Mountain Press Publishing Company, Missoula: Montana. 1988.
Wikipedia en.wikipedia.org. Articles: “Sandstone,” “Siltstone,” “Eocene,” “Oil Shales.”
Local brochures and state park flyers
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