Welcome to
Peterborough's Hidden Geo-Gem
A very simple EarthCache to highlight the landform that has been formed through weathering action of wind, rain and wave
"The soft limestone rock of these cliffs was formed between 10 and 25 million years ago,when the area was under the sea. The sea retreated and deep, vertical joints formed in the rock. Rainwater and spray percolated down the joints, dissolving the rock and widening the cracks. The sea advanced again at the end of the last Ice Age, reaching its present level about 6000 years ago. Since then waves have been attacking and undermining the rock, producing the cliffs that are present today. Harder rock remains as the headland. Waves continue to erode the softer underlying rock, causing caves and arches." - Parks Victoria
What you'll discover here is what is in the process of happening along the coast here and what has been occuring along the Great Ocean Road over thousands of years, but on a smaller scale.
Here you'll find two more examples of arches and sinkholes that have formed here over many, many years.
Sinkholes are common where the rock below the land surface can naturally be dissolved by water and as the rock dissolves, spaces and caverns develop underground. The land above the cavern usually stays intact until there is not enough support and that is when a collapse of the surface will occur.
Questions to log this EarthCache
Q1 At the listed coordinates, estimate the height from the rocks below to the bottom of the arch, also, estimate the thickness of the arch.
Q2 At WP1, estimate the dimensions (depth and width) here and what can you also see at the bottom towards the ocean?
Q3 Comparing GZ and WP1, in your own words how have they formed and which do you think has formed earlier - GZ or WP1 and why?
Hope you enjoyed this EarthCache & please feel free to upload a photo too 
Please send your answers to
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through Message Center or through email.
Please feel free to log this cache once you've completed the EarthCache requirements while waiting for a response to your answers.
You will need to send me your answers to verify your find for this EarthCache and will most likely hear from me within 24 hours or if in the unlikely event, a correction or more detail is needed
