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Cwmorthin Geology Trail 7 - Water Quality

A cache by North Wales 2016 UK Mega Send Message to Owner Message this owner
Hidden : 7/6/2016
5 out of 5
2 out of 5

Size: Size: other (other)

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Geocache Description:

The Cwmorthin Geology Trail is a short linear walk of 8 earthcaches exploring geological features of interest around the Cwmorthin mines and quarry area. 

Please note, pH paper is required to complete this earthcache, see 'General Information'.

General Information and Warnings

Note the difficulty rating of this earthcache. You need to bring your own pH paper to be able to perform the necessary task to log this earthcache. pH paper (litmus paper) can be found at pet-supply stores (to check the pH of aquariums) or cheaply from online suppliers, and it is simply a strip of paper that, when a sample of water is dropped onto it, turns a certain color, giving a rough estimate of pH.

We will leave some pH paper in Cwmorthin Miners Trail 4 - Peninsula (GC6MXD5). Please check recent logs to see if it is still there. *** There isn't any at the moment as the box has flooded, you will need to bring your own. *** We will try and re-stock it soon. We do always recommend you bringing your own as if you arrive and find the pH paper has been removed or damaged, you won't be able to complete the earthcache. If you use the provided pH paper, please use only 1 piece and be careful to keep the rest dry and in the sealed bag so it is in good condition for other people to use.

Here at Cwmorthin you will find a stunning glacial valley but geologically it can be confusing due to the vast amounts of slate mining and surface quarrying that have taken place here. The earthcaches on this trail focus on both the original glacial features of the valley, and also the interesting slate that has been exposed from underground by the workings. Always remember that the huge piles of slate you will frequently walk over and past were not placed here naturally, this is all the work of man. As you walk around, try and keep an image in your mind of how the valley would have looked before the slate was quarried.

Our earthcache trail keeps to the tracks around the old quarry and mine areas. The mines are extensive and should all be gated and locked. The mines were abandoned because they were too unsafe to work. It is not recommended to climb the spoil heaps or explore away from the paths as there could be hidden dangers, and it’s not recommended to let children or pets run off unsupervised. Also be aware that slate can have a very sharp edge and can cut very deeply, so please treat this area with the respect it requires.

Information about Water Quality

There's unlikely to be an announcement today. "Folks, today's pH value of Llyn Cwmorthin is 6.3!" But pH is quite an important measurement of water. Maybe for a science project in school you took the pH of water samples in a chemistry class ... and here we want to draw your attention to the important part a pH level plays in any water you come across. Not only does the pH of a stream or body of water affect organisms living in the water, a but changing pH in a stream can be an indicator of increasing pollution or some other environmental factor.

So what exactly is pH? pH is a measure of how acidic/alkaline water is. The range goes from 0 - 14, with 7 being neutral. pHs of less than 7 indicate acidity, whereas a pH of greater than 7 indicates alkaline. pH is really a measure of the relative amount of free hydrogen and hydroxyl ions in the water. Water that has more free hydrogen ions is acidic, whereas water that has more free hydroxyl ions is basic. Since pH can be affected by chemicals in the water, pH is an important indicator of water that is changing chemically. pH is reported in "logarithmic units". Each number represents a 10-fold change in the acidity/alkalinity of the water. Water with a pH of five is ten times more acidic than water having a pH of six.

Importance of pH

The pH of water determines the solubility (amount that can be dissolved in the water) and biological availability (amount that can be utilised by aquatic life) of chemical constituents such as nutrients (phosphorus, nitrogen, and carbon) and heavy metals (lead, copper, cadmium, etc.). For example, in addition to affecting how much and what form of phosphorus is most abundant in the water, pH also determines whether aquatic life can use it. In the case of heavy metals, the degree to which they are soluble determines their toxicity. Metals tend to be more toxic at lower pH because they are more soluble. 

As this diagram shows, pH ranges from 0 to 14, with 7 being neutral. pHs less than 7 are acidic while pHs greater than 7 are alkaline (basic). Normal rainfall has a pH of about 5.6—slightly acidic due to carbon dioxide gas from the atmosphere. You can see that acid rain can be very acidic, and it can affect the environment in a negative way.

pH and water quality

Excessively high and low pHs can be detrimental for the use of water. High pH causes a bitter taste, water pipes and water-using appliances become encrusted with deposits, and it depresses the effectiveness of the disinfection of chlorine, thereby causing the need for additional chlorine when pH is high. Low-pH water will corrode or dissolve metals and other substances.

Pollution can change a water's pH, which in turn can harm animals and plants living in the water. For instance, water coming out of an abandoned coal mine can have a pH of 2, which is very acidic and would definitely affect any fish crazy enough to try to live in it! By using the logarithm scale, this mine-drainage water would be 100,000 times more acidic than neutral water.

So what about a slate mine? The metals found in slate could affect pH levels and some types of rocks could affect the pH level. We want to know whether the water here at Cwmorthin is safe - is it safe to swim in or is it safe for fish and other life in the lake? It should be pointed out that there is more to consider than the pH of water when you are deciding whether to go for a swim. The temperature of the water is a factor - cold water kills. Here you will find very sharp pieces of slate under the water due to the spoil heap you are standing on, so swimming is not at all recommended regardless of your pH results.

Logging Requirements (Questions to Answer)

Please e-mail me the answer to the questions via my profile. I do read all answers and try to reply to them all; I may not reply immediately so please do not wait for a reply before posting your find. Ideally, please send your answers at the same time you submit your log, or within a few days of your visit. I do check answers have been sent for every log, if you do not send answers within a week your log may be deleted. You are not expected to have any previous geological knowledge, your best attempt at the answers is all that is required.

1. Please take a piece of pH paper and dip it into the water. Compare it against the chart that came with your testing set for the result. Please tell me the pH level of Llyn Cwmorthin.

2. Explain what the results of your test tell you about the water quality of Llyn Cwmorthin? Is the pH of the water safe to swim in? Would it be suitable for aquatic life? (The diagram above will help, remember, rainwater is slightly acidic at 5.6, neutral would be 7)

3. Briefly explain what result you were expecting. If you didn't get the expected result, can you offer a suggestion as to the reason why not?

4. What other factors would you need to consider before deciding if it was safe to swim here?

We always like to see photographs of you and/or your GPS device with the geological features - plus this also provides additional proof of your visit, so please include one with your log if you wish.

This cache has been produced especially for the

Additional Hints (Decrypt)

Guvf vf na rnegupnpur - gurer vf ab obk uvqqra urer, cyrnfr qba'g gel naq frnepu sbe bar. Ernq gur znva yvfgvat sbe zber vasbezngvba.

Decryption Key


(letter above equals below, and vice versa)



131 Logged Visits

Found it 127     Write note 2     Publish Listing 1     Owner Maintenance 1     

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**Warning! Spoilers may be included in the descriptions or links.

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Coordinates are in the WGS84 datum

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