Towerhouse Woods Bubbling Pond EarthCache
Towerhouse Woods Bubbling Pond
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Difficulty:
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Terrain:
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*Please bring a thermometer with you to this Earthcache if you can*
This cache highlights and explains the reasons why this pond bubbles in the way it does.
The pond in the south of Towerhouse Woods is unlike most ponds you will see. For many centuries, gas bubbles have always been seen constantly rising to the water's surface, 24 hours a day, 365 (or 366) days a year, without stopping. The river feeding the pond doesn't bubble, so why does this unusual phenomenon occur?
Many previous theories have been put forward and since rejected, including a mythical one that a dragon breathing out fire causes the pond to bubble!
From a more scientific perspective, analysis by a national energy company has found that the gas that rises from this pond is 92% air and 8% carbon dioxide. A further study by an environmental company found that the water in this pond was, on average, between 2°C and 10° warmer (dependent on time of year) than other nearby bodies of water, including upstream from the river that feeds it.
They concluded that the water had to be thermal in origin, and was likely heated by an underground hot spring- heat rises, so the naturally warmer bubbles to, and burst on, the surface. The water is only slightly thermal, averaging 15°C, which is hot enough to bubble but cool enough for pond life to comfortably live in the water.
Geothermal Springs
The South-West of England has unusually high levels of geothermal activity; the most well-known example is the city of Bath. Closer to home, Hotwells in Bristol is named after the hot wells that rise up from the River Avon.
However, this area is not near any plate margins, not near volcanoes. The water here is instead heated in a different way- the rocks that make up the underlying geology (Carboniferous Limestone) is permeable, meaning it allows the groundwater (old rainwater stored in the ground) in the pond to seep (percolate) into the rock until it reaches a depth where the rocks which are naturally hotter as they're closer to the mantle (the area of inner earth below the crust at a temperature of +500 °C). Underlying rock that is 1km below us can be 30°C hotter than the surface! As a result, the water becomes heated and rises to the surface without a considerable drop in temperature.
The underlying rocks also contain minerals which react with the water to produce air and carbon dioxide bubbles- which are rising to the surface causing the bubbles you see here.
To claim a find on this Earthcache, you must answer the questions below in an email/message to me within 24 hours of logging a find. Any drastically wrong or incomplete answers or any logs from a cacher without sent answers risks their log being deleted. Any photos that reveal answers will also be deleted.
1. To prove this is a thermal spring, the water temperature should be noticeably higher than average tap water temperature (5°C). Dip your finger into the pond, do you think this is the case? If you remembered to bring a thermometer, take a temperature reading.
2. Describe the plume of the bubbles. Do they rise slowly or quickly? Do the bubbles rise individually or as a group? Do they all burst at once or at different moments?
3. Are there any areas that bubble more than others, or don't bubble at all? Do you see any steam?
4. (Proof of visit question) Look at the small island in the middle of the pond. How many trees are on it?
Please also take photos of yourself/GPS as the cache site if you can. As well as being nice to see, it will help to strengthen the proof that you visited, to prevent armchair logging. However, to comply with Earthcache rules, this is optional.
As part of the 13th International Earthcache Day (October 2015) I challenged myself to place an Earthcache every month until Earthcache day 2016, kicking it off with GC62T8F. This Earthcache is the 13th and final in that challenge (October 2016).
Additional Hints
(Decrypt)
[Don't forget the thermometer!]
Treasures
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