Geologists are experts in the art of....
An easy walk across the sands, however a bit of climbing over the rocks will be required once you get there so sturdy footwear is recommended. (I was able to do it in thongs okay).
Welcome to Geurilla Bay!
Guerilla Bay rocks are some of the oldest rock formations on the east coast of Australia - dating as far back as the Ordovician period some 450 million years ago (some debate this particular fact as 510 million years ago!). These rock structures were laid down possibly during an interval of subduction in what was the ancient Pacific Ocean, before becoming part of the Gondwanaland continent incorporating Australia, Antarctica, India, South America and Africa.
What is a Subduction Zone?
A subduction zone is an area where tectonic plates collide together, with one plate overlapping and overriding the other; the subducted plate - the plate underneath - can sink to great depths in the Earth's mantle. Through the high temperatures and pressures associated with this process, seabed sediment is converted to rock. Although plate movement only occurs at a rate of centimetres per year (comparable to fingernail growth rates), an active zone such as in Japan or New Zealand, can cause massive tsunamis and earthquakes.
Rock formations at Guerilla Bay
The rocks at Guerilla Bay consist mainly of feldspathic greywacke, chert and shale of the Wagonga Group that has been squeezed, bent and broken after formation, possibly as a result of compressive movement within the ancient subduction zone. The Guerilla Bay rocks now contain of a mix of fragments called tectonic melange. Also evident in the chert rocks are tooth-like microfossils (less than 1mm) from the gut of extinct eel-like animals: however a microscope is needed to see these minute fossils. What can also be found is some quartz. a hard mineral consisting of silica, found widely in igneous and metamorphic rocks and typically occurring as colourless or white hexagonal prisms.
What is Shale?
Shale is a fine-grained, clastic (composed of broken pieces of older rocks) sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments (silt-sized particles) of other minerals, especially quartz (crystal structure - the second most abundant mineral in Earth's continental crust, after feldspar) and calcite (basically calcium carbonate crystals). The ratio of clay to other minerals is variable. Shales are typically composed of variable amounts of clay minerals and quartz grains and the typical colour is gray. Addition of variable amounts of minor constituents alters the color of the rock. Shale rocks are those that are made of clay-sized particles and are have a laminated appearance. They are a type of sedimentary rock. Shale is the abundant rock found on Earth. They are usually found in areas where gentle waters have deposited sediments that become compacted together.
Logging Requirements:
1) Take a photo of yourself (or something that identifies you is perfectly ok) up on the top part of the rock formation (like the example in the description - great views here too!)
2) Describe the rock prominent at GZ and identify it.
3) What colours can you seen in the rock formations at GZ? Why do you think they are this shape?
4) Much of the shale has veins that run through it. What colours are the veins? Which abundant mineral is predominately seen in the vein?
Please MESSAGE your answers to me using the the link at the top of the page underneath the name of the cache.
This method is preferred and I will reply promptly upon recieving your message. Otherwise an email is OK too!
Feel free to log your "Found It!" in the meantime, if any problems occur I will let you know
Enjoy your time caching here!