Dillon's Battle Earthcache
Dillon Hall.
Located on the campus of the University of Windsor, Dillon Hall was built in 1928 and named for Basilian priest Daniel Dillon, president of Assumption College from 1922 to 1928. It is listed on Ontario’s Heritage Register with a 2010 restoration project undertaken to preserve the building’s beloved cupolas, limestone roof towers, and stone walls. "Assumption College" is engraved above the arched stone entry surround of the main doors. Originally the high school building for the college, now the building is a centerpiece of the University. The coordinates bring you to the front of the building to appreciate its picturesque grandeur and learn about the battle with weathering.
Weathering.
Weathering describes the destructive processes where exposed rocks demonstrate a change in colour, texture, composition, firmness, or form, with little or no transport of the loosened or altered material. Weathering causes a rock to deteriorate over time into soil and rock fragments. Weathering happens in place. It breaks rocks down into substances which may be more easily transported (ie: rock fragments), but are not actually transported during the process of weathering. When those products of weathering are transported to a different location then we may say that erosion has taken place.
Weathering is a very slow process but the rate of weathering of an individual rock can, and does, vary, depending on how the rock was formed and what environmental conditions it is exposed to. The chemical composition of the rock, how hard the rock is, and how porous the rock is all impact on the rate of weathering of individual rock types in the same environment, and even to different parts of a single rock.
Types of Weathering.
There are three types of weathering; (1) Physical, (2) Chemical, and (3) Biological.
Physical weathering is caused by changing temperatures and causes rocks to fracture. It is most common in mountain regions or deserts. One example is when a crack in the rock fills with water. When it freezes, it expands and acts like a wedge widening the crack. As the temperature rises, the ice melts and the enlarged spaces left behind fill with water to continue the process.
Chemical weathering is caused by a chemical reaction with the mineral grains in the rock. One example of chemical weathering is a rock that blackens with pollution or reddens with oxidation. Rain, air pollution, oxidation are all examples of chemical weathering.
Biological weathering is caused by living organisms. Examples include plant roots growing into and expanding cracks in rocks. Algae and lichens that live on the rocks and produce chemicals that help break down rocks. Biological weathering may also be caused by animals burrowing into the rock.
Limestone.
A major building component of Dillon Hall is limestone. Limestone is a carbonate sedimentary rock that is often composed of the skeletal fragments of marine organisms such as coral, foraminifera, and molluscs. Its major materials are the minerals calcite and aragonite, which are different crystal forms of calcium carbonate (CaCO3). This rock surrounds the main archway as sculpted and carved stone. Additionally it comprises the cupolas of the building. Limestone areas of the building are predominantly affected by chemical weathering when rainwater, which contains a weak carbonic acid, reacts with limestone. This causes the limestone to dissolve. Evidence of chemical weathering can be seen in areas where limestone is exposed to the elements. This weathering is further increased by ‘acid rain’ (rain that is more acidic because of dissolved pollutants such as sulfur dioxide and nitrogen oxides).
References.
Limestone. Wikepeida (online).
How does weathering affect limestone?. https://www.internetgeography.net/topics/how-does-weathering-affect-limestone/ (online).
Tarbuck, E., and Lutgens, F. Earth: An Introduction to Physical Geology. Pearson Prentice Hall, 2005.
In order to log this Earthcache, you must email / message wiji (see profile) the answers to the following questions:
1. At the posted coordinates, you are at the entrance to Dillon Hall. Compare the colour and texture of two perpendicular sections of the stone around the entrance. Do you observe any color variations on the stone? How does the texture (run your fingers along the stone) of the exposed stone facing outward compare to the stone face perpendicular to it (the face of the stone that is under the entrance way). Why do you think these differences exist? What is the main type of weathering that contributes to your observations?
2. Prior to 2010, most of Dillon Hall was covered in lush green ivy, growing up to the roof top! Why do you think the ivy was removed? Based on your reading, what type of weathering is this an example of?
3. OPTIONAL - Take a photo of your GPSr or yourself/team with Dillon Hall in the background. You may include this photo in your log.
++ Congratulations to Eca_74 and MickieWalker on the FTF!! ++