This EarthCache is on George Street, Halifax, and is easily accessible to those in wheelchairs, mobility scooter, prams, and on foot. The location is the panels on the side of the building, the panels look like crazy paving, there is no need to look at the floor when doing this EarthCache. So what are we here to look at? Well Breccia. Now, depending on where you come from, Breccia may be pronouced differently, but for certain it is nothing to do with Breakfast.
So what is Breccia?
Breccia is a rock formed by pieces of other rocks, known as clasts, which are then cemented together in what is known as a matrix. Imagine a collection of different broken biscuits held together by chocolate - that is a matrix. In the case of breccia, the matrix is formed by a natural cement.
Breccia can be formed by a variety of ways :
Consolidation - such as the collection of material at the bottom of steep slopes.
Cataclastic -during the process of faulting.
Volcanic - composed of ash and chunks of lava.
Hydrothermal - caused by fluid fracturing the rock mass.
Impact - from when a meteor hits the ground, it fractures the rock at the impact site.
Classification :
Matrix supported - where the clasts do not connect with other, and the matrix surrounds each clast.
Clast supported - where the clasts touch other, and the matrix fills the holes.
Clast size -
The clasts which make up the breccia, can be described in the terms of their size:
Fine (2 - 6mm).
Medium (6 - 20mm).
Coarse (20 - 60mm).
Very coarse (> 60mm).
If all the clasts are mostly the same size, it can be said that the breccia is well sorted, if there is a mixture of clast sizes, then the breccia is poorly sorted.
Breccia is basically made up of a collection of rocks, thought his can also be described, as if there is more than one type of rock present, then it is polymictic, and if there is just one type of rock, it is monomictic.
Please look at the Breccia, and answer the following questions :
1. Please use the above information to classify what type of Breccia there is here.
2. Using a measuring tape, please measure across its diameter the largest clast how big is it. Please describe its shape
3. Is this breccia polymictic or monomictic?
4. Looking at the breccia, please describe the colours of the rock.
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.