At the posted coordinates, you will find a granite monument remembering Major General John P.C. Shanks located on the grounds of the Jay County Courthouse. While Major General Shanks is interesting for his biography, the weathering on the back side of the mounment is just as interesting.
Chemical Weathering
There are three types of external processes that help shape the earth:
- Weathering—the disintegration and decomposition of material at or near the surface
- Mass wasting—the transfer of rock material downslope under the influence of gravity
- Erosion—the incorporation and transportation of material by a mobile agent, usually water, wind, or ice
Weathering is one of the most common we see and that can be see in two ways
- Mechanical weathering - Breaking of rocks into smaller pieces
- Chemical weathering - Chemical transformation of rock into one or more new compounds
Chemical Weathering alters the internal structures of minerals by removing or adding elements. The most important agent is water. Oxygen dissovled in water oxidizes materials. Also, carbon dioxide (CO2) dissolved in water forms carbonic acid and alters the materials.
Chemical Weathering in Granite
Granitic Rocks are Igneous Rocks that are Felsic, which means they are composed of light-colored silicates—quartz and feldspar. Common ones are granite, rhyolite, obsidian. How granite weathers is through the potassium feldspar producing clay minerals, soluble salt (potassium bicarbonate), and silica in solution while the quartz remains substantially unaltered. Also, the Weathering of silicate minerals produces insoluble iron oxides and clay minerals.
Blackening can occur when acid rain, pollutants, and biological organisms such as algae and lichen make prolong contact with the stone’s surface. The growth of algae, moss, or lichen on the surface of the granite can create a dark, unsightly layer. The porous nature of granite makes it susceptible to the growth of lichen, moss, and algae. These organisms thrive in damp, shaded areas and can gradually discolor the stone.
LOGGING REQUIREMENTS
Please complete the tasks and questions below, and send me your answers. If logging for a group, please include the names of everyone in your group.
- Describe the backside of the memorial. What is different about it compared to the front? Why do you think this is the way it is? (Hint: you make want to look at the top of the memorial as well)
- Based on your observations, do you believe this marker has always been in this location? Why or why not?
- Take a photo of yourself (or personal item) with the bronze information plaque with Shanks' name on the front of the monument. Do not attach a picture of the back side since that could spoil people. You can attach it to your found it log (optional).