Visiting Bridge of Allan, I walked past this attractive fountain. I have a few earthcaches where the fountain is made of more than one type of stone and a comparison can be made, but this one is only made from igneous granite. However, it is showing some weathering that's less common in a harder igneous stone.
There is plenty of parking available on the streets nearby.
1) Granite has been chosen for the fountain - given the purpose of the fountain, why would this be a good choice rather than sandstone
2) Describe any weathering you can see on the front of the fountain?
3) Using the information below, what type or types of weathering do you think has taken place here?
4) Take a photo of yourself at GZ, or an identifying item, being careful not to reveal any of the answers to the questions.
Please submit your answers via message though the Geocaching website or by sending me an email - there is no need to wait for a response before logging your find.
Differing permeability of rocks
Sandstone is a sedimentary rock. Sedimentary rocks are typically composed of particles that are loosely packed together. These particles, such as sand, silt, and clay, settle and accumulate over time through processes like erosion and deposition. Due to their loose arrangement, sedimentary rocks often have higher permeability, allowing fluids like water to flow more readily through their pores and fractures. However, this also means they are easier to carve, which makes them a popular choice for more ornate flourishes on buildlings.
The fountain is made from granite, an igneous rock. In contrast, igneous rocks form from molten magma that cools and solidifies either underground (intrusive) or on the Earth's surface (extrusive). This process usually results in a tightly interlocking crystalline structure, making igneous rocks less permeable compared to sedimentary rocks. The dense, crystalline nature of igneous rocks restricts the movement of fluids through them, resulting in lower permeability overall.
Types of Weathering
Weathering is the natural process by which rocks are broken down, decomposed, or their colors altered over time. This can happen due to the effects of water, air, chemicals, or the activities of plants and animals.
Chemical weathering occurs when the minerals within rocks undergo chemical changes, which can alter the rock’s shape, texture, or color. This type of weathering can be driven by substances like carbon dioxide, oxygen, water, or natural acids.
Mechanical weathering is the physical breakdown of larger rocks into smaller pieces without altering the rock's mineral composition. This type of weathering can result from forces like frost, ice, plant roots, flowing water, or heat from the sun.