This Earthcache is in the Carnarvon Gorge NP, a sandstone gorge full of natural wonders to explore. The other Earthcaches in the area will give you a good idea of what to expect.
To get to the posted coordinates, park your chariot at the parking coordinates and follow the main trail for about 10km. About 100m past Cathedral Cave follow the clearly marked path towards Battleship Spur lookout. For a more relaxed visit, book a campsite at the Big Bend remote camp and make it an overnight experience. If you are doing the Great Walk, you will pass this location.
This is not an easy walk, come prepared, check the QPWS website for park updates, and bring plenty of water for the walk.
The Tufa that you can observe here is a modern rock, which means that is currently forming - that is pretty cool considering that most rock that we encounter are formed tens or hundreds of million years ago.
Tufa is a kind of limestone that is formed when minerals precipitate out of cold water, forming carbonate deposits.
Not to be confused with the volcanic Tuff or the Tavertine produced by hot springs.
Tufa will almost always form in the presence of plants, the formed rock is highly porous with a high content of biological matter.
Tufa can form in a wide variety of environments, ie
- Fluvial deposits include Springs or Seeps, Braided channels, Barrages, and Cascades
- Speleothems, Tufa formations in caves include Stalactites and Stalagmites, these lack the biological component and are closer to travertine
Modern tufa is formed from alkaline waters, supersaturated with calcite. As the waters exit the rock CO2 gas is released, resulting in an increase in pH. As carbonate solubility decreases with increased pH, precipitation is induced. Supersaturation may be enhanced by factors, for example, increased air-water interactions at waterfalls may be important, as may photosynthesis.
Tufa can be observed forming at a few locations if Carnarvon Gorge, to claim this Earthcahe, follow the Boowinda Gorge and head up towards Battleship Spur Lookout. At the posted coordinates you can observe Tufa close-up as you make your way up the narrow canyon from Boowinda Gorge. The Tufa here forms a horizontal band, clearly different from the surrounding sandstone.
A few simple questions to answer based on your observations at the coordinates.
- What is the colour of the Tufa? Why do you think it has this colour?
- What texture does the Tufa have? How does this compare to the surrounding Sandstone?
- Why do you think the Tufa is formed here?
- Can you observe any Tufa on the other side of the narrow canyon? Why do you think this is?
Please include a picture of yourself or your Geocaching name and the large boulder at the coordinates in your log.
The creator of this Earthcache at the posted coordinates, boulder in background
You may log your find straight away but remember to send your answers within two weeks of logging your find.
Source:https://en.wikipedia.org/wiki/Tufa