Clifden Caves 🇳🇿 EarthCache
Hidden : 1/1/2019
Difficulty:
2.5 out of 5
Terrain:
4 out of 5

Size: Size: other (other)

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Geocache Description:


Limestone caves

Limestone caves are the most common type of cave in New Zealand and the world. Limestones are rocks containing high levels of calcium carbonate. The limestone at Clifden formed in the early Miocene time (c. 22-18 million years ago) from the accumulation of shell fragments, sand and pebbles in a shallow sea. This sediment was buried and compressed beneath further layers of sediment and later folded, uplifted and eroded to form the present land surface.

Limestone caves form over a long period of time when acidic groundwater seeps through cracks in the rock and dissolves the calcium carbonate in the surrounding limestone. This creates passageways and unusual formations such as stalactites and stalagmites that gradually become larger and form cave systems.

The Clifden Caves feature some spectacular formations on the ceilings and walls. Refrain from touching cave formations as they have taken millions of years to form and are very fragile.


Dripstone

The most common stalactites (A) and stalagmites (B, C) are speleothems, which occur in limestone caves. They form through deposition of calcium carbonate and other minerals, which is precipitated from mineralized water solutions. Limestone is the chief form of calcium carbonate rock which is dissolved by water that contains carbon dioxide, forming a calcium bicarbonate solution in underground caverns.




Limestone stalactites

Stalactites (A) are the spikes hanging from the roof of a limestone cave.

An average growth rate is 0.13 mm (0.0051 inches) a year. The quickest growing stalactites are those formed by a constant supply of slow dripping water rich in calcium carbonate (CaCO3) and carbon dioxide (CO2), which can grow at 3 mm (0.12 inches) per year. The drip rate must be slow enough to allow the CO2 to degas from the solution into the cave atmosphere, resulting in deposition of CaCO3 on the stalactite. Too fast a drip rate and the solution, still carrying most of the CaCO3, falls to the cave floor where degassing occurs and CaCO3 is deposited as a stalagmite.

All limestone stalactites begin with a single mineral-laden drop of water. When the drop falls, it deposits the thinnest ring of calcite. Each subsequent drop that forms and falls deposits another calcite ring. Eventually, these rings form a very narrow (≈4 to 5 mm diameter), hollow tube commonly known as a "soda straw" stalactite. Soda straws can grow quite long, but are very fragile. If they become plugged by debris, water begins flowing over the outside, depositing more calcite and creating the more familiar cone-shaped stalactite. The same water drops that fall from the tip of a stalactite deposit more calcite on the floor below, eventually resulting in a rounded or cone-shaped stalagmite. Unlike stalactites, stalagmites never start out as hollow "soda straws". Given enough time, these formations can meet and fuse to create pillars of calcium carbonate known as a "column".

Stalactite formation generally begins over a large area, with multiple paths for the mineral rich water to flow. As minerals are dissolved in one channel slightly more than other competing channels, the dominant channel begins to draw more and more of the available water, which speeds its growth, ultimately resulting in all other channels being choked off. This is one reason why formations tend to have minimum distances from one another. The larger the formation, the greater the interformation distance.


Limestone stalagmites

Stalagmites (B, C) are the spires projecting upwards from the floor of the cave.

Stalagmite formation occurs only under certain pH conditions within the underground cavern. The partial pressure of carbon dioxide in the water must be greater than the partial pressure of carbon dioxide in the cave chamber for conventional stalagmite growth.

If stalactites – the ceiling formations – grow long enough to connect with stalagmites on the floor, they form a column.

Stalagmites should normally not be touched, since the rock buildup is formed by minerals precipitating out of the water solution onto the existing surface; skin oils can alter the surface tension where the mineral water clings or flows, thus affecting the growth of the formation. Oils and dirt from human contact can also stain the formation and change its color permanently.


Glow worms/titiwai

Glow worms/titiwai (Arachnocampa luminosa) are a feature of some cave systems. New Zealand glow worms are the larvae of small flies called fungus gnats which undergo a four stage life cycle: egg, larvae, pupae and adult fly. Only the larvae can feed and produce light. This ‘glow’ is used to attract prey which is caught in sticky silk threads that hang from the glow worm nest. These silk fishing lines are then hauled in and the captured insects devoured. The glow worms grow up to 2.5cm before developing into pupae and adult fly stages.

The Clifden Caves provide a natural habitat for the glow worm, which requires a damp environment with little or no wind.


Questions:

1. When walking through the cave, how big is the largest stalactite and stalacmite you can see?
2. Have a closer look at the largest stalactite you can see. Please describe its features (e.g. length, colour, form, etc.). What do you think, how long did it take for the stalactite to be formed?
3. Pick a stalactite. How many drops can you count within 3 minutes?
4. There are 3 ladders in the cave. How many rungs does each one of them have? (optional)


Log entries:

"Clifden Caves was a memorable experience as I love an underground adventure"
"It was truly impressive and a lot of fun. (...) Another real highlight of our vacation." 💙
"This was a very cool spot to explore." 💙
"A cracking cave walk 🤩🤩🤩"
" Wow! This is just a brilliant location." 💙
"Fave point worth earth cache that’s for sure" 💙
"A beautiful place and an amazing experience of a lifetime." 💙
"Great fun" 💙
"Definitely one of our favorite NZ spots so far, (...) thanks for the epic EarthCache!"
"These caves were the unexpected and unplanned highlight of the whole NYs road trip for me!" 💙
"And if someone would ask me now what was the best part I would for sure say Clifden Caves!!" 💙
"An amazing cave - not what we expected at all."
"This is an amazing place and just a wonder of nature."
"Wow this was quite an adventure." 💙
"Very cool place, (...) seeing mostly no one but a few glowworms." 💙
"Wow what an adventure." 💙
"What a great place to explore."
"A wonderful experience and a {FTF} as well." 💙
"Thanks for the earthcache was a great one and we look forward to returning again." 💙
"Clifden Caves - one of the best experiences in New Zealand!" 💙


sources: https://www.doc.govt.nz/parks-and-recreation/places-to-go/southland/places/clifden-area/; https://en.wikipedia.org; https://de.wikipedia.org

Additional Hints (Decrypt)

znc

Decryption Key

A|B|C|D|E|F|G|H|I|J|K|L|M
-------------------------
N|O|P|Q|R|S|T|U|V|W|X|Y|Z

(letter above equals below, and vice versa)


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