Skip to content

Slate fencing EarthCache

Hidden : 08/14/2015
2 out of 5
2.5 out of 5

Size: Size:   other (other)

Join now to view geocache location details. It's free!


How Geocaching Works

Please note Use of services is subject to the terms and conditions in our disclaimer.

Geocache Description:

At the given coordinates, you will find unusual fencing formed of slabs of slate. Your task is to examine the slate and read the descriptions below, then complete the questions given below.

Slate Fencing

The best way to reach the coordinates is to start at Abergynolwyn railway station, which is a little way west of the village. There is free parking here, or you can catch the little train from Tywyn. There is a footpath towards Nant Gwernol, which goes from half-way up the drive, indicated with a red arrow labelled "Station's Link Path". Follow this path for about 300m until you reach the level crossing. Do not walk along the railway track! There are some steps on this path, so it is not suitable for buggies or people in wheelchairs. Alternatively, you can park in Abergynolwyn. From the village, walk out on the main road towards Tywyn, to a point shortly after the roadside footpath ends. Walk up the forestry road on the left to the level crossing, where the footpath from the station also crosses. Note that this is not a public road, so you cannot reach the cache by car.

When you reach the destination, you will find a fence made out of slate. This type of fencing is unusual, if not unique to this area of Wales. Please stay on the footpath side of the fence - trains may be running throughout the year, even if no passenger service is in operation!

Rock types:

Rocks can be generalised into three categories: Igneous, Metamorphic and Sedimentary.

  • Igneous rocks are formed from the cooling of volcanic lava or magma (molten rocks below the surface of the Earth), which solidifies into solid rock. They can be formed under the surface of the earth (intrusive) or on the surface after a volcanic eruption (extrusive). Over 700 types have been identified, with different properties depending on their composition and the pressure and temperature conditions in which they were formed. Typical examples of igneous rocks include granite (intrusive) and basalt (extrusive). Igneous rocks form approximately 65% of the Earth's crust.
  • Metamorphic rocks are formed from older rocks, of any type, being subjected to high temperatures (greater than 150°C) and/or pressures (greater than 1,500 bars) which cause the rock to change in form, in a process known as metamorphism. These extremes can be found due to magma intrusions heating the surrounding rock (contact metamorphism), pressure deep beneath the Earth's surface (burial metamorphism) or a combination of both (regional metamorphism). Metamorphic rocks often form layers of different widths, in a process known as foliation. Typical examples of metamorphic rocks include gneiss and marble. Metamorphic rocks form approximately 27% of the Earth's crust.
  • Sedimentary rocks are formed when particles of older rocks or organic materials (for example shells of sea creatures) accumulate and bind together in a process known as cementation. The sediments forming the rock can be caused by weathering or erosion. These particles are compacted at the Earth's surface, at lower temperatures and/or pressures than those required for metamorphism. Typical examples of sedimentary rocks include sandstone and limestone. Sedimentary rocks form approximately 8% of the Earth's crust.

About slate and Bryn Eglwys:

The use of slate dates back to Roman times, as its properties make it ideal for use as roofing materials. It is hard and durable, but may be easily split into thin sections. It was formed when older rocks such as mudstone or shale are compressed and heated. The pressure causes lines of foliation, perpendicular to the direction of pressure, which allows slate to be easily split, making it an ideal material for roof tiles. Slate may sometimes contain fossils; this is generally regarded as poorer quality and less suitable for roofing.

Slate mining at Bryn Eglwys near Abergynolwyn began in the 1840s, and reached a peak in the latter half of the 19th century. There are three veins of slate found at Bryn Eglwys, known as the "Broad Vein", "Middle Vein" and "Narrow Vein". The Broad Vein contains layers of shale with patches of slate. It does not split into thin sections, making it unsuitable for roofing. The Middle Vein contains low quality slate that contains a lot of fossils. The Narrow Vein contained the best quality slate, and was the vein most worked at Bryn Eglwys.

Production at Bryn Eglwys declined during the twentieth century due to introduction of cheaper manufactured roofing tiles and the increased difficulty in extracting the remaining slate. Some slate mining still continues at Penrhyn quarries in North Wales, though the quarries at Bryn Eglwys at Abergynolwyn closed permanently in 1946 after a serious roof fall.

About the railway:

The narrow gauge railway you will see here was built in 1865 to carry slate from the nearby quarries at Bryn Eglwys to the main line at Towyn (now spelt Tywyn). Previously pack-horses had carried the slates over the hills to Aberdovey, then a thriving port. The line was the first narrow gauge public railway to be steam-hauled from the start. In 1910, the railway and quarries were bought by the local MP, Sir Henry Haydn Jones. Although the line never made a profit for him, he determined to keep the line open, even after the quarries had closed. The line suffer from neglect and under-investment, so when Haydn Jones died in 1950 it seemed certain that the line would close. However a group of enthusiasts formed the world's first railway preservation society to keep the line open. They took over operation of the railway, rebuilt the track and acquired more locomotives and carriages. Nowadays the railway is an important tourist attraction in this part of Wales.

Information adapted from Wikipedia

Your tasks:

In order to claim this cache, you must visit the site and examine the slate. Also read the descriptions of slate and the different classifications of rock above, then complete at least the first three tasks below:

Task 1: Examine the slabs carefully, looking for evidence of fossils. Can you find any? What does this tell you about the quality of the slate?

Task 2: Describe the colour and texture of the slate. From your observations and the descriptions above, do you think slate is igneous, metamorphic or sedimentary?

Task 3: You will find another slab of slate at these coordinates of a similar size that does not form part of the fence. What is it used for? What does this tell you about the properties of this slate?

Task 4: (Optional) Post a photo of yourself or GPS unit at the site - though please don't give away the answer to task 3.

Logging this cache:

Once you have found the cache, make a note of the answers and send them to me by email or message (preferred). You may log this cache without waiting for a response, though I will reply to let you know if you are correct or not. I reserve the right to delete logs if I feel there is no understanding of the answers, or if I don't receive the answers within 14 days of your log. (If for any reason you cannot answer in this time, please indicate this in your log). Good luck!

Hall of fame:

  • FTF: The Gummidges
  • STF: ttTom
  • TTF: clare.unitt

Additional Hints (Decrypt)

Jura ybbxvat sbe sbffvyf, gnxr pner abg gb or pbashfrq ol znpuvavat znexf be yvpura

Decryption Key


(letter above equals below, and vice versa)