Tunnel Vision EarthCache
Please note Use of geocaching.com services is subject to the terms and conditions
in our disclaimer.
This Earthcache is to be done from in the tunnel, looking up. DO NOT attempt to go onto the railway lines above the tunnel.
A simple Earthcache-and-dash, suitable for beginners as an introduction to Earthcaching. Of course, it's available for everyone to do!
There is no physical container; instead you must answer questions based on an Earth science lesson at GZ.
This Earthcache highlights the presence of, and explains the formation of, stalactites in this railway tunnel.
An example of stalactites growing at London's Victoria station. (Photo courtesy of Islalou*)
Stalactites (also called stonicles- 'stone icicles') are deposits of materials that hang from the ceilings of of structures made of rock- usually caves, but sometimes in man-made buildings like this tunnel.
They are formed on concrete structures when a soluble material or a material that can be carried in water (such as minerals, mud, sand, lava etc.) dissolve into, or is carried by, water. This water will then seep through the structure and begin dripping from the ceiling. When the water comes into contact with the air, a chemical reaction occurs, and the material deposits and solidifies. Over time, with repeated deposition and solidification, the stalactite grows.
In this case, the material is limestone and it has been dissolved into the water. For anyone interested in the chemical equation for this reaction, it is:
You can see all over the inside and outside of the tunnel, white material (calcium carbonate) has been deposited, but not yet formed stalactites.
Note: Some stalactites are within arm's reach. Please do not touch them- not only might they snap, but a single touch can permanently stop them from growing, as skin oils can alter the chemical reactions that make them grow.
To claim a find on this Earthcache, you must answer the questions below and email/message me (via my profile) within 24 hours of logging a find. Any drastically wrong or incomplete logs or logs from a cacher with unsent answers will have their logs deleted. Any photos that reveal answers will also be deleted.
1) Stalactites in these conditions grow, on average, 1cm per year. Using this information, estimate how many years the longest stalactites have been growing for.
2) The bridge is not made of limestone. Where do you think the limestone for the chemical reaction comes from? Think about what is above the tunnel.
3) a) What colour(s) are the stalactites?
b) Are the tips of these stalactites pointy or rounded?
4) What features usually grow directly below stalactites and why won't they grow here?
5) To prove you visited: What is the code for this bridge? This is the series of numbers and letters that follow the word 'Shrubs' on the red and white sign.
6) (Optional) Add a photo of you/your GPS in the tunnel WITHOUT SHOWING ANY OF THE STALACTITES.
A torch would be required in evenings, nights, and other times of low light, hence the attribute.
As part of the 13th International Earthcache Day (Oct 2015) I challenged myself to place an Earthcache every month until Earthcache day 2016, kicking it off with GC62T8F. This Earthcache is number 5 in that challenge (February 2016, published very late).
Additional Hints
(Decrypt)
Dhrfgvba 4 znl erdhver n yvggyr erfrnepu. (Gur srngher'f anzr nyfb ortvaf jvgu fgnyn-)
Treasures
You'll collect a digital Treasure from one of these collections when you find and log this geocache:
Loading Treasures