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Read the lesson below, visit the location, answer the following questions and send them to me by e-mail:
1. In your own words, how does chemical weathering work?
2. Which type of chemical weathering is most likely in action on these rocks? Could there be more than one type in action?
3. What type evidence of chemical weathering are you observing on the rocks?
4. Bonus question…Lichen are covering nearly all of the rocks at this location. Check out the “Lichens of Georgia” site (listed in Sources below) and tell me which lichen you think are present. 5. With your "found it" log, include a photo of you or your group while at the overlook. Optionally, you can take a photo of a personal item such as a geocoin or a piece of paper with your geocaching name.
5. With your "found it" log, include a photo of you or your group while at the overlook. Optionally, you can take a photo of a personal item such as a geocoin or a piece of paper with your geocaching name.
If your answers are profoundly off, I’ll contact you. Otherwise, please log your find after you send an e-mail. In the e-mail, please indicate your geocaching name and include the names of other geocachers with you. Logs without accompanying answers sent will be deleted without notice. According to the guidelines, sending the answers is a requirement, not a request.
Weathering is the breaking down of rocks, soil, and minerals as well as wood and artificial materials through contact with the Earth's atmosphere, water, and biological organisms. While some sources indicate there are only two main categories, mechanical and chemical, other sources include biological as well. All three types truly “interact” and “support” one another and the weathering process overall. This EarthCache though will focus on how chemical weathering works.
Chemical weathering is the weakening and subsequent disintegration of rock, or the formation of new minerals by chemical reactions. Given enough time, chemical weathering can create dramatic results. Some, but not all, of the chemical weathering processes require water to be present and they happen more rapidly at higher temperature, so warm, damp climates best facilitate many of the processes. Chemical weathering can still take place in polar regions, just at a much reduced pace.
Chemical weathering only affects the surface of a rock, but as the rock is broken down by other means (i.e. mechanical and biological), more surface area of the rock is exposed, thus allowing chemical weathering to begin and occur in these new areas.
There are three main types of chemical weathering, with a fourth also discussed by some sources:
Oxidation – In this process, the rock minerals are interacting chemically with oxygen in the air, changing the mineral composition. When these minerals oxidize, the become less resistant to other forms of weathering. This is the same process that forms rust on tools.
Hydrolysis – Here we have water dissolving minerals in the rock, typically producing new compounds. This process is not always readily observable, but sometimes you can see the process in action, such as when water interacts with calcite in caves, causing them to dissolve. The calcite in the dripping water then builds up over the years, creating stalagmites and stalactites.
Solution – This is mineral interaction with various acids. During hydrolysis, acids may sometimes be produced, but it can also happen when water mixes with carbon dioxide. This creates carbonic acid which is important to the creation of caves and sinkholes where there is limestone. Stronger forms of acid are created when different polluting gasses, such as sulphur dioxide or nitrogen oxide, mix with rain, creating acid rain. Over time, these solutions can serious damage rock and building made of certain material.
Biological – This may seem a bit out of place since it is sometimes listed as a major category of weathering. It really comes down to biological weathering can be both physical or chemical. Lichen are a major component of biological/chemical weathering and consists of fungi and algae living together in a symbiotic relationship. Fungi release chemicals that break down rock minerals; the minerals thus released from rock are consumed by the algae, eventually creating holes and gaps that can be exploited by other means of weathering.
Depending on the geography, the geology of the region and the type of process occurring, chemical weathering can either be readily apparent or not. For oxidation, the clear sign that it is happening is the rusty colored hue that a rock will have. As described above, hydrolysis can easily be seen in caves, but it also occurs when water comes in contact with granite. Feldspar crystals inside the granite react chemically, forming clay minerals, which weaken the rock. The process of solution can easily be seen on many surfaces, as surfaces become pitted over time. Finally with biological, you can easily see the lichen on the rock, but you can also see the results as discoloration and pitting on the rock surface.
At 9,049 acres, Georgia’s largest state park is a hiker’s and backpacker’s haven. More than 40 miles of trails, including the popular 23-mile Pine Mountain Trail, wind through hardwood and pines, over creeks and past small waterfalls. Many visitors are surprised to find rolling mountains 80 miles southwest of Atlanta. Above King’s Gap is Dowdell’s Knob where President Franklin D. Roosevelt sometimes picnicked and pondered world affairs. A life-size sculpture of the president now welcomes visitors to the overlook.
Park Hours
7am – 10pm
Dowdell's Knob April–September 8 a.m.–8 p.m. October–March 8 a.m.–5 p.m.
Fees and Passes: Daily $5 parking fee but annual passes are available.
FDR State Park: https://gastateparks.org/FDRoosevelt
en.wikipedia.org/wiki/Weathering
www.thoughtco.com/examples-of-chemical-weathering-607608
georgiawildlife.com/sites/default/files/wrd/pdf/lichens_poster.pdf
www.geolsoc.org.uk/ks3/gsl/education/resources/rockcycle/page3564.html
passel.unl.edu/pages/informationmodule.php?idinformationmodule=1124303183&topicorder=5&maxto=6
Geology for Dummies
Geology: A Self-Teaching Guide
Understanding Earth, 6th Edition
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