St Laurence's Church, Ludlow

To claim a find for this EarthCache you must visit the location given and make some observations. Then you must find the answers to the questions below and either email (for a quick reply) or use the geocaching message system, to send them to me.

I reply to email quickly and will endeavour to reply to the messages within a few days.

You are invited to log your find for this cache and send your answers simultaneously but if you can't you must send answers within 10 days of logging or face a possible deletion of your found log.

Also should you wish to include a photo that would be find but no spoilers of the wall please.

Right, that's the admin sorted, now to the EarthCache lesson.

The focus of this EarthCache is the walls of the church and the condition they are in, I will ask you to describe the walls and explain why they look like they do.

First a Little history of the church

Saint Laurence's Church was established as a place of worship when the Normans founded Ludlow in the late 11th century. It is situated in the centre of Ludlow on the hill around which the medieval town developed and can be seen from outside the town as it towers over the rest of the town. The church is a member of the Greater Churches Group and is the largest parish church in Shropshire.

There are original traces of a Norman church which were found beneath the south porch during excavations, indicating some foundations exist from the 11th century AD. After its initial construction the church was expanded and rebuilt by local support and subscription in 1199 to accommodate a growing town population. In 1400s considerable wealth accrued in the town based upon the local wool trade. Correspondingly the church underwent several further additions during that time. The major works occurred between 1433 and 1471 with a virtual re-building of the nave, the huge tower and chancel. The tower took on a Perpendicular style which was the preferred style of the late 15th century in England. Saint John's Chapel on the north side was the chapel of the Palmers' Guild, which thrived during this time. The Palmers' Window within St John's Chapel illustrates the legend of King Edward the Confessor and S John which is depicted by eight panels and was inspired by the Ludlow Palmers’ 13th century pilgrimage to the Holy Land.

So to the EarthCache (finally)

This church's façade is constructed from a red soft sandstone. Sandstone is formed as particles or grains of rock settle out of water or air over many thousands of years and compact under its own weight followed by cementation to form rock. Slowly it piles up deeper and deeper until all the water and air is squashed out, a cementation process occurs and rock is formed. A poorly cemented rock will weather quickly and not make a good building stone.

Depending on the donated material and grain size rock can be very hard or quite soft and though harder more compacted rock is better for building, often local stone is used for building despite it not being the best material. Economic pressures were present even in the 11^th century it seems. At this location a red sandstone has been used and this rock is not the hardest material so has suffered from erosion and weathering and this is the focus of this EarthCache.

Let me explain about the processes of weathering and erosion.

Weathering

Here is a simple definition of weathering

Weathering is the breaking down or dissolving of rocks, soil and minerals in situ on Earth's surface. There are three types of weathering and they are physical, chemical and biological. Weathering does not involve the removal of the materials, we'll come to that later.

Here is some information of how the three types of weathering occur.

Physical weathering

Physical weathering also called mechanical weathering is caused by the changing of volume of a material within or on the rock. This type of weathering occurs when rocks are broken down by physical factors in the environment, such as wind, water, and temperature change. Importantly physical weathering does not change the chemical composition of the rock. There are three types of physical weathering.

1. Frost wedging or freeze-thaw weathering primarily occurs in temperate humid climates. Water gets into cracks in the rock and when the temperatures fall the water will freeze. When water freezes it expands, by on average 9%, this puts pressure on the surrounding rock. This cycle will eventually put enough pressure on the rock to causes pieces to fall off.

    

2. Salt crystallisation occurs in semi-arid environments, where the evaporation of water from rock surfaces leads to the crystallisation of salts. Crystallisation leads to a dramatic increase in volume which exerts pressure on the surrounding rock, and can eventually fracture the rock having the same effect.

    

3. Thermal expansion usually occurs in arid regions. During the day temperatures rise and heat the rock. As the rock heats up it expands slightly. Then at night, when temperatures fall, the rock also cools and contracts. This cycle leads to exfoliation where the top layers of rock peel away.

All the three processes above result in small, or sometimes large pieces breaking off as the volume of the rock or minerals or water in and on the rock expand and contract repeatedly.

Chemical Weathering

Chemical weathering is the breakdown of rocks because of the interaction of air, water or acid with the chemical composition of the rock. There are four main different ways in which this can happen and here is a short description of each.

1 Oxidation occurs when oxygen reacts with minerals such as calcium and magnesium to form iron oxide. Iron oxide is reddish brown in colour and causes the decomposition of rock.

2 Hydrolysis occurs when water reacts with minerals in the rock causing the chemical composition of the rock to change and become more unstable. This reaction makes the rock more susceptible to decomposition.

3 Carbonation occurs when carbon dioxide from moisture in the air reacts with carbonate minerals found in rock. This creates carbonic acid which breaks down rock.

4 Solution occurs because many minerals are soluble and are removed when they come into contact with water as it dissolves.

Biological weathering

Biological weathering is the breakdown of rock by plants, animals and micro-organisms. For example plant roots can enlarge cracks in a rock as they grow and expand or animals can burrow or scratch into rocks or earthen materials causing pieces to be broken off or removed.

Erosion

Here is the simple definition of erosion

Erosion is the geological process by which earthen materials like rocks, soil or sand are worn away and transported by natural forces such as wind or water. The transportation element is important here because its the transportation of the materials that makes it erosion. Erosion is the removal of the particles to another location usualy by wind; blowing the particles away, water; washing the materials elsewhere or ice; breaking small or even large chucks off as the ice expands. Animals can also be responsible for erosion by their constant use of familiar paths or moving of materials during building processes,

Right so now you have looooooaaaads of information about weathering and erosion and it's time for a couple of questions about the walls of the church.

I'd like you to look closely at the walls of the church, you can observe the section close to the door or go into the gardens and look from there. You do not need to touch the walls and I'd like you to find a section that looks like it has seen many many years of hard wear.

1 Please describe the stones on the wall, concentrate on colour, shapes, and apparent texture.

2 Tell me what erosive and weathering processes the worn sections of the walls have suffered and remember to explain you thinking with examples from the text above.  

NB the lower sections of the wall, close to the ground, may have suffered more due to dampness from the ground, please bare this in mind when you prepare your answers.

Thanks for attempting this cache, I hope you found it interesting and informative.

Please send your answers and log your find at the same time and if you include a photo don't include the rock of the church.

treboR

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