Pen y Fan Pond EarthCache EarthCache

This EarthCache has been developed with the intention of introducing the Geocacher to an interesting piece of geology located at Pen y Fan Pond, which is located north of Pen y Fan Industrial Estate in Oakdale, near Blackwood. The distance covered to complete this EarthCache is only a small part of the Pen y Fan Country Park.

The accuracy of the content of the EarthCache description is the responsibility of the EarthCache owners. Please let us know if you have any comments/corrections.

Pen-y-fan Pond is a popular summertime family destination which offers safe, flat, open spaces to picnic, fly a kite, kick a ball or take an easy ramble.

Experienced walkers can use the park as a base to explore the beautiful and historic countryside around Manmoel. Fishing is permitted on the pond but please make sure you get your day ticket (available from Pontllanfraith Leisure Centre) beforehand. Further water activities on the pond occur through the Caerphilly Adventure Group.

Parking Charges

Parking charges have been introduced, by Caerphilly County Borough Council / Cyngor Bwrdeistref Sirol Caerffili, at Pen y Fan Pond from the 11 August 2014. The charges apply to all users including disabled badge holders. If a vehicle is left unattended, with no obvious signs of a parking ticket having been purchased or displayed on the windscreen, or if the ticket is showing as being after its expiry time, the vehicle may be issued with an Excess Charge Notice. There is very limited parking outside of the Pen y Fan Pond park area. You are advised not to park on the main road.

2. COMPLETING THE CACHE

2.1 EQUIPMENT REQUIRED

You do not need any special equipment to complete this EarthCache just, if it is raining, waterproof clothes or an umbrella, a notebook and a pen or pencil. A camera, magnifying glass or hand lens and a grain size scale or ruler would be useful but are not requirements.

Hammers, chisels, acid bottles, trowels, etc, are not necessary and are not allowed.

Please upload as many pictures as you want as long as they do not provide any of the answers to the questions associated with this or other nearby caches.

The intention is that the features described in this EarthCache are fully accessible to all Geocachers at all times. However, some of the nearby facilities are seasonal. This applies to the toilets (which are accessible for people with disabilities) and the café kiosk. Basically these are closed at night and during the winter months.

2.3 DISTANCE/TIME

Completing this EarthCache involves a walk of about 300 metres as a minimum. This should take about 20 minutes (including collecting the required information). However, we would encourage all visitors to walk around the pond. There is a good footpath following, for most of the circuit, the water’s edge.

Where possible we have provided co-ordinates for the features described below.

The questions in this EarthCache relate to the geological features described and visited at this EarthCache site. Please visit the area and do not simply try to find the answers by Internet research.

To ensure that you visit the site there is one requirement to confirm that you visited the area (this is detailed in the LOGGING THE CACHE section below and at Location 4).

We have presented the questions and logging requirement within the cache description text and collected them together at the end to help Geocachers who want just a single question and answer sheet. However, you may need access to the full text of the cache description in order to answer them.

Pen-y-fan Pond is a canal feeder reservoir. It was used to hold water that could be added to the Monmouthshire and Brecon Canal which ran from Brecon to Newport Docks. As there is evidence of glaciation at this site this EarthCache is about glaciers and evidence of glaciation events.

The word glacier comes from French. It is derived from the "nonstandard" (as opposed to "classical") Latin glacia and ultimately from Latin glacies meaning ice. The processes and features caused by glaciers and related to them are referred to as glacial. The process of glacier establishment, growth and flow is called glaciation. The corresponding area of study is called glaciology.

A glacier is a large persistent body of ice that forms where the accumulation of snow exceeds its melting and sublimation (that is, the process of transformation directly from the solid phase to the gas phase without passing through an intermediate liquid phase) over many years, often centuries. The snow which forms temperate glaciers is subject to repeated freezing and thawing, which changes it into a form of granular ice called névé. Under the pressure of the layers of ice and snow above it, this granular ice fuses into denser firn. Over a period of years, layers of firn undergo further compaction and become glacial ice.

There are two broad types of glacier: continental glacier (or ice sheets) and alpine glacier. Only two true ice sheets exist today. These are in Greenland and Antarctica. Alpine glaciers form on the crests and slopes of mountains and are also known as "mountain glaciers", "niche glaciers", or "cirque glaciers".

The most recent glacial maximum peaked 18,000 years ago and is considered to have ended 10,000 B.P. (before present). However, little ice ages have occurred since then.

Following the little ice age, around 1850, the glaciers of the Earth have retreated substantially through the 1940s. A slight cooling led to the advance of many alpine glaciers from 1950-1985. However, since 1985 glacier retreat and mass balance loss has become increasingly ubiquitous and large.

This EarthCache looks at the evidence left behind by glaciers at Pen y Fan Pond.

There are a number of answers to this question. These include:

1. Glacial valleys: Alpine glaciers change V-shaped valleys to U-shaped. Continental glaciers remove all soil, plants, and small hills. When a glacier moves along its valley it will erode the surface beneath it. Areas of softer rock may be eroded more easily. Also, the glacier may be joined by a tributary glacier to increase its power to erode.

2. Fjords: Glaciers carve fjords in valleys where they travel. A fjord is a long, narrow valley with steep sides carved by glacial movement. A fjord represents the seaward end of a deeply excavated glacial-trough valley that was partially submerged by drowning after melting of the ice.

3. Ribbon Lakes: When the glacier retreats, the deepened sections fill with meltwater and become lakes. Deposition of moraine across the valley can also act as a dam, trapping the meltwater and thereby creating a ribbon lake. Ribbon lakes are long, narrow lakes found on the valley floors of glacial troughs. They can be formed due to a combination of erosion and depositional processes.

4. Corries, arêtes, pyramidal peaks and glacial troughs: These are all features created by glacial erosion. At the 'start' of a classic valley glacier is the cirque, which has a bowl shape with escarped walls on three sides, but open on the side that descends into the valley. In the cirque, an accumulation of ice is formed. These begin as irregularities on the side of the mountain, which are later augmented in size by the coining of the ice. Once the glacier melts, these corries are usually occupied by small mountain lakes called tarns.

There may be two glacial cirques 'back to back' which erode deep into their backwalls until only a narrow ridge, called an arêtes is left. The meeting of three or more arêtes creates pointed pyramidal peaks and in extremely steep-sided forms these are called horns. This structure may result in a mountain pass.

5. Drift: Drift is any material deposited by glaciers or their meltwater.

6. Glacial till: Till is that unsorted material that is deposited directly by ice. Glaciers leave behind deposits known as glacial till, which are unstratified, poorly-sorted sediments. Glaciers move a wide range of sedimentary particles from small clay-sized particles (sometimes referred to as ‘glacial flour’ formed by rock grains of a size between 0.002 and 0.00625 mm) to large boulders. When the glacier either melts or retreats, these poorly-sorted sediments are deposited. These deposits are known as tillite in lithified sedimentary rocks.

7. Drumlins: Drumlins are asymmetrical, canoe shaped hills with aerodynamic profiles formed of till. They are elongated features that can reach a kilometre or more in length, 500m or so in width and their heights vary from 15 to 50 meters. There is still some debate about how drumlins are formed, but the most widely accepted idea is that they were formed when the ice became overloaded with sediment. It is common to find several drumlins grouped together. A collection of drumlins is called a swarm.

8. Moraine: The term moraine is of French origin. Moraine is a type of landform, with linear features, that is created when a glacier deposits the material (till) that it has been transporting. It is made up of unsorted angular rocks. There are several types of moraine. A mound or ridge of till (unstratified glacial drift) is deposited when a glacier begins to retreat or melt. As the glacier grows and extends, it pushes glacial drift at its front forming a mound of debris. This glacial drift is then dropped in place when the glacier retreats or melts which creates a terminal moraine. Medial moraines, which are formed by the conjunction of two glaciers, are also deposited as a glacial melts. Glaciers erode the sides of the valleys in which they travel. Therefore, when two glaciers unite (in much the same rivers unite), a line of glacial drift (medial moraines) from both glaciers is formed.

9. Erratics: The larger pieces of rock which are encrusted in till or deposited on the surface are called glacial erratics. They may range in size from pebbles to boulders, but as they may be moved great distances, they may be of drastically different type than the material upon which they are found. Patterns of glacial erratics provide clues of past glacial motions.

10. Scrape marks or striations: Glaciers leave scrape marks behind on the rocks on which they travelled. Visible characteristics of glacial abrasion are glacial striations. These are produced when the bottom's ice contains large chunks of rock that mark scratches in the bedrock.

The above is only a short introduction to the evidence of glaciation. However, with this information you should be able to complete this EarthCache.

To complete this EarthCache you need to visit Pen y Fan Pond Country Park. If travelling by car the entrance to the park is to the north of the Pen-y-fan Industrial Estate, signposted from Oakdale on the B4251. As an alternative you could go by bus (Service 52 - Blackwood to Abertillery – but check times before setting out).

If travelling by car and parking on site, leave your vehicle at either Location 1 or Location 2. All Locations listed below are fully wheelchair accessible.

Location 1 N 51° 42.013 W 003° 9.737.

This point is the location of one of the two car parks at Pen y Fan Pond and is the recommended trailhead for this EarthCache. The approach to the EarthCache site (Location 3) and Proof of Visit Question site (Location 4) are slightly downhill from here.

Location 2 N 51° 41.964 W 003° 9.680.

Alternative car park. The approach to the EarthCache site (Location 3) and Proof of Visit Question site (Location 4) are slightly uphill from here.

Location 3 N 51° 41.981 W 003° 9.752.

Once at Pen y Fan Pond Country Park make your way to Location 3. Here you will find evidence of glaciation.

Question 1. Examine and describe the evidence of glaciation that you find at Location 3.

Question 2. How long has it been here?

Question 3. Based on the information given in this cache description what is this object?

Question 4. How do you think that Pen y Fan Pond was formed? Look carefully at its shape and location. If stuck go to Location 5 (N 51° 41.814 W 003° 9.801 – if in a wheelchair, travel around the lake in a clockwise direction to avoid a barrier) where the answer should be obvious.

Location 4 N 51° 41.972 W 003° 9.714.

Question 5. Here you will find an information board. Give four (short) reasons why Pen y Pond is special. This is the logging requirement and must be completed correctly.

Location 5 N 51° 41.814 W 003° 9.801.

You only need to come here if you have difficulty in answering Question 4. However, if you have time it is well worth completing the walk around the pond.

We have collected the questions and logging requirement together so that they can be copied and pasted onto a single sheet should you want a paper version. However, you will need access to the full text of the cache description in order to answer them.

Question 1. Examine and describe the evidence of glaciation that you find at Location 3.

Question 2. How long has it been here?

Question 3. Based on the information given in this cache description what is this object?

Question 4. How do you think that Pen y Fan Pond was formed? Look carefully at its shape and location. If stuck go to Location 5 (N 51° 41.814 W 003° 9.801 – if in a wheelchair, travel around the lake in a clockwise direction to avoid a barrier) where the answer should be obvious.

Question 5. Here you will find an information board. Give four (short) reasons why Pen y Pond is special. This is the logging requirement and must be completed correctly.

Email the answers to the Questions 1 to 5 to us via the link in our profile. Please do not put the answers to the questions in your log entry, even encrypted. You do not need to wait for a reply before making your log. However, we request that you email the answers to us on the same day that you make your log. Any logs that do not fulfil all requirements will be deleted.

Logging Requirement. There is one logging requirement to confirm that you visited the area. This requirement should be completed at Location 4 and is detailed in Question 5.

Photographs from your visit are very welcome with your log. Feel free to upload any, except those that assist in answering the Questions, photographs you take during your visit to the EarthCache site. We may even replace the current Figures using your pictures.

Please let us know (either in your log or through our profile) what you think of this EarthCache – was it useful in extending your knowledge of geology, was it too difficult, or any other constructive comments.

Picture credits are given under the appropriate Figure. If there is no credit we took the picture.

Note: the primary source of the material used to prepare the cache description was:

Wikipedia, the free encyclopedia.

Permission to place this EarthCache has been given by Countryside and Landscape Service / (Gwasanaeth Cefn Gwlad a Thirlunio, Caerphilly County Borough Council / Cyngor Bwrdeistref Sirol Caerffili.

Congratulations to PlasmaWave for their FTF.