An easy Earth Cache that mightn’t show you the most spectacular rocks you have ever seen but it will teach you a little and enable to you collect a smiley for your troubles.
I read about the Rosedale Horst while researching another EC awhile back, GC5R118 here Coorabin Clay. We often stop in Rosedale for lunch (try the Bakery it is great) and hadn’t noticed anything remarkable in the way of rocks, so we were keen to check it out on our next visit.
I tried to do some research form home but came up empty handed; I made several attempts to contact the Rosedale historical society but no reply. Armed with the knowledge given to me by Google I arrived in town with Geo daughter (4) to find and view the Horst, as we drove down Prince street she yelled “Look Mummy there it is”, proudly pointing at the Patrobas monument (the only Gippsland racehorse to have won a Melbourne Cup). I had a good chuckle and had to explain that was a Horse and we were looking for a HORST! She screwed her face up and said: “What is that?”
I stopped at the Newsagency and ask if the newsagent knew about the Rosedale Horst, he said with great confidence that it was just at the other end of the block in the park and all the information was on the sign. Excitedly arriving at the park I was once again looking at Patrobas….the frustration must have shown on my face as an old timer walking past ask if I needed assistance, I explained I was looking for the Rosedale Horst. His reply with a cheeky grin… “ I think you mean Horse love and it’s right behind you!”
Sigh!
So to answer the question, "What is a Horst?" we have turned to Wikipedia;
In physical geography and geology, a horst is the raised fault block bounded by normal faults or graben. A horst is a raised block of the Earth's crust that has lifted, or has remained stationary, while the land on either side has subsided. Horst is Dutch and German for heap.
The Vosges Mountains in France and Black Forest in Germany are examples of horsts, as are the Table, Jura and the Dole mountains. The word is also applied to larger areas, such as the Russian Plain, Arabia, India and Central South Africa, where the continent remains stable, with horizontal table-land stratification, in distinction to folded regions such as the Eurasian chains.
In geology, a graben is a depressed block of land bordered by parallel faults. Graben is German for ditch or trench. The plural form is either graben or grabens.
A graben is a valley with a distinct escarpment on each side caused by the displacement of a block of land downward. Graben often occur side-by-side with horsts. Horst and graben structures indicate tensional forces and crustal stretching.
Graben are produced from parallel normal faults, where the displacement of the hanging wall is downward, while that of the footwall is upward. The faults typically dip toward the center of the graben from both sides. Horsts are parallel blocks that remain between graben; the bounding faults of a horst typically dip away from the centre line of the horst.
We eventually did find the Horst, we were a little underwhelmed when we found it and now understand why so many locals had no idea what we were looking for. Although not spectacular we felt it was still a good Earth Science lesson.
The nearby Cliffs of the Horst have a large content of Kaolin. kaolinite, Al4(OH)8[Si4O10, and other related clay minerals such as nacrite and dickite. Kaolin is considered to be the most important and common mineral in clay used in pre-historic pottery. Kaolin is still very important today, it’s a part of our daily lives and we don’t even realise.
Kaolin deposits are commonly classified into two types Primary (residual) deposits formed by in-situ hydrothermal alteration and/or leaching and weathering of such feldspar-rich rocks as granite, syenite or gneiss. Secondary (transported) deposits, these are composed of detrital clay derived from residual deposits formed by sedimentary processes.
To successfully log this Earth Cache we require you to consider the information given, check out the reference points and perhaps if you need to do some research of your own, then message us with the following answers to the best of your ability;
1. At the published coordinates you will see a sign 9. Geology of the Ridge at Rosedale. What are the cliffs comprised of? Can you see any signs of this when you look at them in the distance? What colour is it?
2. Are you standing on the Graben or the Horst?
3. To answer this question you need to visually compare the water in the nearby Latrobe River and nearby Dam. What is the colour difference and what does that indicate with regards to the nearby cliffs?
4. Exposed rock face reference point S 38° 08.445 E 146° 47.608 : No need to stand right at this point or cross the road, view it from a safe distance and please watch littlies near the road. What can be seen in the exposed rock face, what has caused this exposure and colour?
5. A photo of your team or GPS nearby. (Optional)
You are welcome to log your answers straight away to keep your TB's and Stats in order but please message us with your answers within 24 hours. Cachers who do not fulfil the Earth Cache requirement will have their logs deleted.
,
Source: Wikipedia