The coast in and around Port Hughes and Moonta Bay are lined by steep cliffs of Hindmarsh Clay, these cliffs line the coast for 3km and range from 10-20 metres tall in parts.
These cliffs are known as a "sea cliff" and are formed by wave erosion. Waves crash against the cliff until a notch is formed, eventually this repeated action leads to the cliff becoming unstable and collapsing. The process continues and causes the sea cliff to retreat.
Evidence of this process can be seen by the aforementioned notches, a distinct indentation which range from a few centimetres up to several metres in height and depth. These are most commonly found in steep cliffs like the ones at Port Hughes as the gradiant makes it more susceptible to notch formation. However, can form in any cliff under the right conditions. The presence of salt and tidal oscillations (the back and forth movement of water) also increase the chances of notch formation.
These cliffs are also vulnerable to another form of erosion known as gullying, caused by rainfall. This process is especially bad after heavy storms as rock faces can become extremely weak due to the volume of water flowing over it.
This has a profound impact on area's surronding the cliff face, such as vegeation vital to protecting the sandunes. It also impacts other risks of the shoreline and wildlife:
♦ Public safety
♦ Loss of animal habitat
♦ Loss of cliffs of geological significance
♦ Loss of heritage listed sites
This and the notches formed by wave erosion mean the cliff is being eroded away by two different forces, hence the double whammy. This creates an issue for the geological signifance and animal habitats located here.
Logging Requirements:
Observe the cliff face from the beach and answer the following questions:
1. How many notch layers can you see? What does this mean?
2. Describe the colour and texture of the cliff face. Please use more then one word.
3. Can you see any evidence of gully erosion? If so where and what has it done to the cliff face?
4. Can you see what may help the stop the cliff erosion?
5. Take a photo of you, your stamp or personal item with GZ in the background.
Please send answers via the Geocaching message centre or to my email, answers posted in the logs will be deleted.
You can log the find immediately, if answers are supplied to CO within 14 days.
Happy caching!
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