St. Mary's Priory Church in Chepstow was founded as a Benedictine priory around 1071-1072, with its blonde Norman west doorway dating from the early 12th century. Following the Dissolution of the Monasteries, much of the original priory was demolished, leaving only the nave to serve as the parish church. Over subsequent centuries, it underwent alterations, including the collapse and rebuilding of its tower in the 18th century and further Victorian restorations, resulting in the mix of architectural styles seen today.
We were staying nearby and I often looked at the weathering on the front of the building as I walked in and out of town, it creates lots of interesting shapes in the stones.
As you'd expect, there are several different types of weathering all taking place at the same time.
1) Look at the front of the church - where can you find evidence of
a) spalling?
b) dissolution weathering?
2) Use the weathering on the carvings around the door to explain why carved areas are a good indication weathering is taking place.
3) Do you think all the blocks on the front are original? Why might they not be?
4) Visit the doorway on the east side of the church (see the waypoint - head left around the exterior of the church when facing the front entrance). The carving in the doorway here shows less weathering - give a reason why you think this is.
4) Take a photo of yourself at GZ, or an identifying item with the church clock visible.
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.
Weathering on Carved Areas
Intricate carvings often show more chemical weathering than flat blocks because they have more surface area exposed to the elements. The curves and bumps mean more of the stone can directly touch rainwater and air. This allows chemical reactions, like minerals dissolving, to happen faster. Also, the carved shapes can hold onto water and dirt for longer, letting these chemical processes work more effectively and cause more damage to the details over time.
More exposed areas of stone, such as protruding features or those facing the prevailing wind and rain, tend to weather faster than recessed areas like the inside of doorways, as they are subjected to the full force of the elements without shelter.
An example of chemical weathering on carvings in Bristol:
Spalling
Spalling is a common type of physical weathering where thin layers or flakes of rock break off from the main surface. This often happens when water seeps into tiny cracks or pores within the stone, then freezes and expands, pushing layers apart. Repeated cycles of freezing and thawing cause these layers to weaken and eventually detach. You can often spot spalling as the stone surface looks like it's peeling or has lost its outer 'skin'.
An example of spalling:
Dissolution Weathering
A type of weathering you might observe, especially in rocks like sandstone, is dissolution weathering. This is a chemical process where certain minerals within the rock are dissolved by water. Rainwater, for example, is naturally slightly acidic, and when it comes into contact with minerals like calcite (which can act as a 'cement' in some sandstones), it can slowly dissolve them away. In a coastal location, the presence of salty water can sometimes speed up this process, as the salts themselves can attract and hold moisture, or contribute to chemical reactions that further break down soluble minerals. This removal of material often leaves behind hollows, grooves, or a generally pitted surface on the stone, as the more soluble parts are eaten away, while the more resistant grains or areas remain.
An example of dissolution weathering:
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If you would like to add to the Church Micro series yourself then please visit
http://churchmicro.co.uk/
There is also a Church Micro Stats & Information page that can be found at
http://www.15ddv.me.uk/geo/cm/index.html
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