There was a fair swell, with the low pressure system off-shore, but a few of us never-the-less were on that rock ledge (the wave-cut platform below Boiling Pot) for the highest tide for this year. Dronehack Dan filmed the event, with commentary from me. To be sure to know when this little YouTube is online subscribe for my irregular emails.
WHAT ARE MARINE POTHOLES?
Marine potholes are formed by the relentless grinding of boulders – of a harder material perhaps granite – into softer sandstone, after being caught in a depression.
Pounding surf will cause the harder rock to swirl round and round, eroding away and creating a circulation marine pothole.
The grinding, that created these potholes, could only have happened when sea levels were higher: when this platform was underwater.
Marine potholes like this can be found along seashores around the world, with a particular width to depth ratio.
It is a fact, that while the chattering class is concerned with sea level rise of about 36 cm over the last 100 years, but the more significant trend is sea level fall of some 1.5 to 2 metres since the Holocene High Stand some 7,500 years ago. The presence of these potholes in platforms above the high tide mark is evidence of this sea level fall.
HOW ARE PLATFORMS FORMED?
Wave cut platforms form just below sea level, in the intertidal zone, where the cutting action of waves will bring down great lumps of rock from above.
The debris will be removed by the wash, beyond the intertidal zone.
The headland will recede landward, as the sea eats into the cliff-face.
And so, cliffs are formed, with wave-cut platforms at their base.
As the cliff retreats landward, the platform will become wider.
It is evident that the waves, even on the highest tide, do not reach to the base of the cliff or across the wave cut platform. This platform is above the highest tides, and quite wide, suggesting that sea levels were much higher and for a period of time.
I wasn’t washed away on Monday 10th February at 9am
This foreshore can be slippery, and it is uneven. Further, to get beyond the pot holes to the cliff face (below Boiling Pot), it is necessary to climb down a vertical sandstone edge with about a two metre drop. So, while it is the case that I encourage everyone to come and see how high the waves break on the highest tide each month, this adventure does require a level of fitness.
Also, rock fishing is one of the most dangerous sports in Australia with 158 deaths in the 13 years to 2017. To reduce the risk of injury Surf Life Saving Australia urges all rock fishers to:
• Wear a lifejacket
• Check tides weather and surf conditions
• Take personal responsibility, think twice and assess your safety
• Plan an escape route in case you are washed into the water
• Wear the right gear i.e. lifejacket, appropriate footwear, lightweight clothing
• Never fish alone, and make sure you tell someone where you are going and when you will be back
• Look for Angel Rings or someone other floatation device to throw to someone in trouble
• Call 000 if assistance is required.
Observation is the most basic form of science, it can also be so cathartic – watching how high the highest waves reach on the highest tide along the seashore.
If you are interested in coming to see this platform on highest tides each month, then I will likely be at the marine potholes 30 minutes before the highest tide, I will then walk on to the cliff face.
The potholes are best accessed by walking to Tea Tree Bay first via the coastal track, and then heading north west along the shoreline.