Preston Park Clock Tower EarthCache

Please read the following lesson, visit the cache site and answer the questions in order to find this Earthcache.

Granite is an igneous rock with a coarse-grained crystalline structure, consisting mainly of quartz and feldspar. Granite can be white, pink or grey, depending on the exact mineral makeup. Granite has been widely used throughout human history as a construction stone, due to its properties of being hard and tough.

Clay is a fine-grained sedimentary material containing particles with a grain size of less than 4 micrometres. It forms as a result of the weathering and erosion of rocks containing the mineral group feldspar (known as the ‘mother of clay’) over vast spans of time. During weathering, the feldspar content is altered by hydrolysis (reaction with water) to form clay minerals such as kaolinites and smectites. Clay minerals have a sheet-like structure and are composed of mainly tetrahedrally arranged silicate and octahedrally arranged aluminate groups. Typically, the erosion of feldspar is performed by streams and rivers, causing the clay minerals to accumulate on the riverbed.

Water is contained in the mineral structure of clay, giving it a plastic structure when wet and a hard, brittle texture when dry. This gives clay great advantages for sculpturing as it is quicker and easier to work with than many materials. The clay is initially soft and malleable, allowing a free and flexible approach with many different tools. Small details that would be difficult to produce using e.g. cast bronze or carved stone, can easily be accomplished in clay. The clay can then be hardened by allowing it to dry- a reversible process- or made even harder by firing it in a kiln, irreversibly converting the clay into a ceramic material. Because of these remarkable properties, clay is very useful as a decorative and building material. Different types of clay are used depending on the desired properties of the final product.

Terracotta (‘baked earth’) is an example of a clay-based material. It has a characteristic reddish colour which is produced when iron reacts with oxygen during the firing process; the exact colour can vary according to the iron content. Terracotta is valuable for outdoor items such as roof tiles and plant pots, because it is relatively heat resistant and water-proof. Terracotta has a long history of use by humans; archaeologists have found terracotta figurines dating from 3000–1500 BC. Architectural terracotta became popular in the West in the 19^th century.

The clock tower was gifted to Preston Park by Edward White, who formally asked the Mayor to dedicate the clock tower to the use of the public. It was designed by Francis May, in the Flemish Renaissance style. The tower is mostly made of red and pink terracotta. Frances May said he chose terracotta rather than white stone because that would have been too ‘sepulchral’ for a park and noted that it was the first clock tower of its kind to be constructed of terracotta.

In order to log this cache, visit the cache site and answer the following questions, which should be sent to the cache owner via e-mail or though the message center. I will respond to let you know if your answers are correct, but you do not need to wait for the response - you may log your find straight away.

Questions

1. On the West side of the clock tower, you will see a founding block laid by Edward White, what is the date on this block?
2. Examine the tower. Identify which parts are made of terracotta and which of granite, and describe their physical appearance. What sort of condition they are each in? Which material is most resistant to weathering?
3. Based on your observations, which do you think is the superior building material, in terms of resistance to weathering? Why do you think the entire tower isn't made of that material? Bear in mind the date from Q1.
4. Name the metal that is the main contributor to the colour of terracotta. Name the mineral that produces a pink colour in granite.
5. What types of rock are granite and clay? Metamorphic, Igneous or Sedimentary?
6. (Optional) Upload a photograph of yourself at the cache site.