This earthcache will take you to a shale outcrop along a trail at the Ross Park Zoo. You will be looking for effects of biological weathering along this rock face.
Ross Park is owned by the zoo, but this cache is located outside of the actual zoo proper. There is an admission fee if you want to visit the zoo, but there is no admission fee to visit this part of the park. No night caching.
LOGGING REQUIREMENTS FOR THIS EARTHCACHE
At the given coordinates you will see a shale outcrop at the Ross Park Zoo which shows signs of biological weathering. Specifically, you will see the effects of plants, both large and small, on the wall.
In order to log this EarthCache, send me your answers to the following questions. Answer the questions below based on your observations at the cache site. I am looking for general answers, not specific. For example, trees are “trees” not “oak trees”.
DO NOT INCLUDE YOUR ANSWERS IN YOUR LOG OR IT WILL BE DELETED.
- List one large sized plant, one medium sized plant and one small sized plant that are probably contributing to the weathering along this outcrop.
- Consider the large sized plant you selected. Are there 1-3 of them, 4-10 of them or more than 10 present along this outcrop?
- Look at the medium sized plants and the small sized plants. Which of these two sizes is most prevalent here?
- Looking at the face of the outcrop. Is there more area covered by plants or more area showing bare rock?
- OPTIONAL – JUST FOR FUN (you can put this answer in your log if you want to, but do not include any information about what type of plant it is): Look at some of the larger plants that are on top and near the edge of the outcrop. Make a prediction about how long you think it will be before one of them falls off the ledge.
- Post a picture of yourself, your GPS or some other object that would identify you as being at the site. Try not to include any spoilers (do not include the outcrop in your picture). Take your picture looking away from the outcrop.
ROCK BREAKDOWN
Over time rocks wear away, and their size and shape change. Some of the processes that cause this might happen relatively quickly while others might take extremely long periods of time. Two general categories of processes are WEATHERING and EROSION.
Weathering is a process which breaks down rocks into smaller pieces. This process does not include the moving of the rocks to other locations. The ultimate result of weathering can be to disintegrate the rock into smaller and smaller particles until it eventually becomes new soil or is moved to a different location through the process of erosion.
Erosion is the process that moves the rocks. It might be seen as soil that has been moved along a streambank, rocks that have been moved downstream by the current, or many other examples. Weathering and erosion often work together. A rock can be weathered creating smaller pieces that can be moved away by the wind or water through the process of erosion.
This earthcache deals with WEATHERING.
There are several types of weathering. A common classification breaks down weathering into biological, chemical and mechanical.
Biological - Biological weathering occurs when living organisms begin to grow on the rock or when animals begin to burrow into the rock.
Chemical - Chemical weathering occurs when the surroundings react with minerals in the rock changing the chemical composition of the rock.
Mechanical - Mechanical weathering is anything that breaks apart rocks without changing their chemical composition. One common example is frost wedging in which water finds its way into cracks in the rock and then freezes. The water expands as it freezes and creates even bigger cracks in the rock. This can eventually lead to very large cracks, or even breaking the rock apart.
This earthcache focuses on BIOLOGICAL WEATHERING.
A Little More About Biological Weathering
There are two basic types of biological weathering – by physical means or by chemical means.
Physical means – Some type of force or pressure is exerted on the rock causing a break down of the material. This might be minor at first, but it exposes the surface to other factors that can speed up the process of degrading the rock. For example, a plant might begin to grow in a layer of soil above the rock, or seeds may fall into cracks in the rock. In either case the roots eventually grow across the area, get larger and over time and increase the size of the cracks. Animals can also contribute to the weathering process. They can create holes in the ground above the rock. Smaller animals can find their way into cracks and crevices which have soil in them. These holes provide a means for rock particles to move to the surface and help to enhance the weathering process. Even humans can add to the process by simply walking on the rock causing soil particles to be crushed into smaller pieces.
Chemical means – Biological organisms can produce a variety of acids and other compounds that tend to break down rock and enhance weathering. Limestone and marble are especially affected by mild acids. Acids can form when plants or animals die on or in the rock. As they decompose they produce organic matter which produces carbon dioxide. Combined with water this produces a weak carbonic acid which degrades the rock surface.
Some Examples of Biological Weathering:
Plants Causing Severe Damage to Grave Stones
Tree Roots That Could Lead to Serious Damage to the Supporting Rock
A Tree Whose Roots Created a Crack Then Widened by Frost Wedging
Lichens Taking Over a Rock