Teddy's Look out, overlooks the Great Ocean Road, most people miss the Earth Lesson on the way to the lookout. This EarthCache will highlight the natural errosion technique known as Concretion.
The Concretion Bowls.
At the listed coordinates, you will see a number of small rock platforms, within these platforms you will see the 'Bowls' (refer to picture above).
This rock outcrop is part of a distinctive series of sedimentaary rocks that formed during the Cretaceous period, around 100 to 120 million years ago. A unique property of these sandstones is that they are composed mostly of Volcanic rock fragments, derived from an arc of active volcanoes to the east.
After they were buried, these rocks were saturated with water that contained various chemical compounds - including calcium carbonate - which slowly percolated through pore spaces and fractures, and precipitated around local features in the rocks. These points became the nucleus for more carbonate to grow over time, layer by layer, into a ball shap. This is 'concretion'.
Here at Teddys Lookout, rainwater is likely to be the main chemical agent in weathering - and you can see the concretions have been completly hollowed out, leaving hemispherical depressions. (Bowls)
There is a different feature with a related earth science lesson about 8km away. You may care to visit GC8GGC8 Cannonball Concretions to see another result of these processes, although with a very different conclusion
How to log this Earthcache
Feel free to log your find, and email the CO your answers to the following questions. (within 5days)
Q1. - With the information above, what period of time were these rocks formed? and how long ago?
Q2. - What are they composed of?
Q3. - What is the main chemical agent known to be the cause of the weathering at this location?
Q4. - Walk around the rock feature, how many 'Bowls' do you see?
Q5 - Touch and Feel the bowls, describe and explain the texture that you feel.
* Photo's/Selfies of the area are optional but always welcomed.
I hope you have enjoyed learning about these rock formations.
* Information courtesy of Professor Andrew Gleadow of the University of Melbourne, in conjunction with the Great Ocean Road Coast Committee Inc.