I was in the area for other caching purposes and was intrigued by the local geology so did some research in a nearby facility, and later at home. At GZ you may have had to cross a small stream, or use the often placed stepping stones. Depending on time of year, and/or your balance, you may need to get your feet wet.
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The local mythology.
Maori legend provides two stories as to the origin of the red rocks. The first describes Kupe, a famous Polynesian explorer, who cut his hand while gathering paua (a shellfish), his blood staining the rocks red. The second describes how Kupe’s daughters feared for their father’s safety during a long voyage, and so cut themselves in their grief and worry, their blood tinting the rocks.
Pariwhero/The Red Rocks.
The Red Rocks (“Pari-whero” in the local Maori language) are given their name from their distinctive coloring. The Red Rocks are made of pillow lava produced 200 million years ago by undersea volcanic eruptions, with iron oxide giving the rocks their unique color. The lava became embedded in younger greywacke stone, giving the stones a beautiful grey and red coloring.
The Red Rocks themselves were formed during the Torlesse period when lava erupted from fissures on the sea floor. As it emerged its outer surface chilled to form a coherent but still plastic envelope which filled with molten lava to form a pillow-like structure. The repeated occurrence of this produced a stacked layer of these structures termed pillow lava. Various iron oxides which were leached as clouds of superheated steam were released into the ocean and formed the red colour we see today. All of this occurred on the sea floor and subsequent uplift has raised the land to where it is today.
Rock colours.
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RED - Whero - Haematite, which forms when the ratio of ferric (oxidised) to ferrous (unoxidised) iron is >40%.
GREEN - Kakariki - This reflects a ratio of ferric to ferrous iron between 25-40%
GREY - If the ratio is less than 25%, the rock will appear grey in colour.
However heat, such as that produced by a beach BBQ, can turn greywacke rock a rusty brown colour. The colours of the South Coast rocks depend on the relative abundance of iron in the rock and how oxidised it is.
The quarry face at GZ and further West is a streaky mixture of greywacke and argillite rocks, as is most of the Wellington region. Pariwhero/Red Rocks is an amalgam from another time, scrapings of subducted seamounts off one tectonic plate and embedded into another.
Earthcache tasks.
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Using the information above and standing at GZ please view the cliff face in front of you;
Q1. What percentage (approx) is the ferric to ferrous here. Please explain your reason for this choice. (in your opinion is it more red (whero) or green (kakariki))?
Q2. At the beach below the area where you are currently standing the gravels and stones are unexpectedly a different colour to the rock face at GZ. In your opinion, how do you think they got there, and what colour would you describe them to be?
Q3. The rock face in front of you has noticeable wedges and terraces cut into it, why do you think these were made?
Please send your answers to these questions to me via Geocaching message, then you may log your find. If you need any further help with the answers please contact me.
Question 4. Please provide a photograph (with a 'Red Rock' somewhere on the foreshore) of yourself or a personal item to prove you visited the site. A personal item such as a handwritten name, or trackable is an option for those who do not want to photograph themselves. This picture should be uploaded with your found it log.
You can log your find as soon as you like after your visit, and your answers have been submitted, don't forget - if you need any help with the questions please let me know.