This EarthCache takes you to Leeds Cathedral, though there is no need to go inside. We are here to look at the main entrance, which is on Cookridge Street, and the stone surrounding it. You are responsible for your own safety.
We are here to look at a type of limestone. Limestone is a sedimentary rock, formed from calcium carbonate. It can be formed by the accumulation of the shells of ancient sea creatures, and also from lime mud. Here there is a type of limestone which is formed by Ooids.
So, what are Ooids? Well, let's first set the background for the stone that you see in front of you. Imagine a tropical sea, and a very small piece of shell falls to the seafloor. The water in this sea, has a high concentration of calcium carbonate, as the small piece of shell is moved about by the current of the sea, calcium carbonate starts to form a concentric layer over it. Eventually, an ooid forms, its shape being circular due to the repeated movement by the sea current. Imagine this happening a million times, and a build up of ooids forms, which over time form a sedimentary rock, which in this case is oolithic limestone.
This being an EarthCache, in order to log it, I ask that you answer the above questions. Please send them to me, and do not include them in your log. You can send them to me by using the message facility or email, both of which can be found by looking at my profile.
1. Please examine the stone surrounding the doorway closely, please describe the oolithic limestone in terms of structure, and colour.
2. Please compare the oolithic limestone to the neighbouring stone which forms the structure of the church. How does this stone differ in terms of structure, feel and grain size?