-
Difficulty:
-
-
Terrain:
-
Size: 
(not chosen)
Please note Use of geocaching.com services is subject to the terms and conditions
in our disclaimer.
In order to count this Earthcache as a find, you must complete the following tasks and email the answers to me.
1. Estimate the height of the “needle” and the size of the “eye’s” opening.
2. What type of weathering is taking place in this area, chemical or physical?
3. Besides the Needles Eye, what other type of erosion can be seen in this area?
4. How do you think erosion happened in such a specific and isolated area?
5. What element do you think had the biggest impact on the creation of the eye, wind, rain, freezing, or thawing? Why?
This Earthcache is located at The Needles Eye, along Needles Highway in Custer State Park. A daily or annual park sticker is required to enter the state park and visit the lake. Incredible scenery can be seen from the Needles Highway and there are several pullouts along the way for visitors to stop and capture the beauty on film. In addition to the scenery, those traveling along the highway will pass through a series of tunnels carved into the granite. As an interesting tidbit, this roadway was carefully planned by former South Dakota Governor Peter Norbeck, who marked the entire course on foot and by horseback. Construction of the road began in 1920 and was completed in 1922. Enjoy!
Geology provides the foundation of scenery in the Black Hills. The central area of the Black Hills is a region of rocks mainly composed of granite. The rocks found throughout Custer State Park are some of the oldest rocks in North America, dating over two billion years in age. Formed underground and now exposed at the surface, this region features a dome-like mass of resistant rocks.
The main focus at this stop is on the Needles Eye that has become one of the most well-known landscapes in the region. The opening in the granite, which resembles the eye of a needle, was created by wind, rain, freezing, and thawing through a process called erosion.
Erosion is the process by which the surface of the Earth gets worn down. Natural elements, such as wind and glacial ice, can both cause erosion. Water is one of nature’s most powerful elements and the most common agent of erosion, simply because there is so much of it on the Earth’s surface. Given enough time, even the greatest works of man will be washed away. The Grand Canyon is one of the best examples of water erosion.
Erosion is happening all around us. Even though you may not recognize it, the forces of erosion are constantly at work shaping our planet. Sometimes, as in a mudslide or avalanche, erosion happens quickly. More often than not, erosion happens so slowly that you can’t even see it. Over time, the simple act of water running downhill can not only carve out a hole the side of the Grand Canyon, but it can literally move mountains. Although erosion is a natural process, it has be increased dramatically by human land use, such as industrial agriculture, deforestation, and the growth of cities.
Before water and wind can carry material away, the sediments, soil, and rocks first need to be broken down through a geological process called weathering. As its name suggests, weathering is controlled by elements things like wind and rain, and it comes in two basic forms.
Chemical weathering happens when substances like water or acids get into the rock and react with the minerals that make up the rock. Think of the process like steel objects rusting when they are left out in the rain. The same thing happens to certain minerals inside rocks. After enough time, these minerals change so much that they simply crumble.
Physical weathering happens when things like ice physically break rock apart. If you have ever left a can of pop in a freezer for too long, you know that when the water freezes to ice, it expands so much that it may actually split the can apart. This same thing happens when rain gets inside rocks and freezes. This process is called “frost wedging.” Through this, solid rock can be reduced to tiny pieces in just a few years.
Once weathering breaks a rock down, it is then moved along by gravity, which leads to the process of erosion.
NOT A LOGGING REQUIREMENT: Feel free to post pictures of your group at the area or the area itself - I love looking at the pictures.
Additional Hints
(No hints available.)