of Ethan Allen Park

Monkton Quartzite: Our study of the geology of Ethan Allen Park began in the parking lot with the boulders that lined the parking lot perimeter. These rocks were classified as Monkton Quartzite. Monkton Quartzite is composed of silt, quartz, and traces of iron oxide, which gives the rock a maroon- purplish color. These rocks were not part of the natural bedrock of Ethan Allen Park, they had been transported there to landscape the park from a different area of Vermont.

Dunham Dolomite: Throughout our geologic study of Ethan Allen Park, we found that there is an overwhelming amount of the dominant rock type called Dunham Dolomite. Dunham Dolomite is a pinkish-tan to buff color and its formation is approximately 550,000,000 years old. There is evidence that the rock originated in an ancient warm shallow ocean because it is composed of limestone, which comes from that environmental condition. Other evidence is that there were sand grains from a beach found in some of the Dunham, as well as thin layers of sediments on weathered rocks. This is due to algae mats that had grown. The algae grows in warm shallow sea water, and traps sediments due to it's sticky texture, the algea then grows through the sediments. This process repeats, and overtime the algae disapears and the sediments remain. The compostion for Dunham Dolomite is...CaCO3---->(Ca, Mg)CO3. A method for distinguishing limestone vs. dolomite is the scratch test. If you pour a weak hydrochloric acid (1M HCl) on the rock and it fizzes, then it is limestone. If the rock only fizzes after it is scratched with a steel hammer, then it is Dolomite. This is a result of increasing the surface area of the rock.

Dolomite Outcrop

Hydrochloric Acid Scratch Test

Chemical vs Physical Weathering: Weathering is the process in which a rock breaks down. A rock can be broken down in two different ways, chemically and physically. Chemical weathing is when a rock's chemical compostion changes. An example of chemical weathering is if Dunham Dolomite dissolves overtime in acid rain. Physical weathering is when the type of substance the rock is made of does not change, but it can change shape. An example of physical weathering is when water gets into cracks in the rock and freezes. Water expands when it solidifies so it creates splits in the rock and serves to break down solid bedrock.

Soil: In studying the geologic compostion of the Ethan Allen Park we also looked at the soil. To examine the soil we dug a 1 meter x 1 meter hole in a soft area of the site. Once the hole was dug, we smoothed out the sides so that we could see the layers in the soil. Several soil horizons were clearly visible. It was found that the soil was moist troughout and the texture of the first horizon was a fine silt, or loam, with occasional stones. Also, the layers were veined due to plant roots and worm tunneling. We then took the Munsell Soil Color Chart and matched each layer with the proper color chip. On the color chart, we used page number 10yr. The rows and columns are of the corresponding color match is written as a ratio (ex. 2/4 = column 2; row 4). We found that the first third of the hole was 10yr 3/3. The second third of the hole was 10yr 4/4. The last third of the hole was 10 yr 4/3.