Welcome to Bellambi Point
Bellambi Point is one of Wollongong’s most scenic coastal spots, where sandstone meets the sea. The rock platform here has been shaped for millions of years by wind, waves, and salt a perfect place to see nature’s slow but powerful work in action. Before you head out, make sure to check the surf and tide forecast twice. Conditions here can change quickly, and it’s safest to visit at low tide with calm seas.
Overview
Bellambi Point is made up of sandstone from the Late Permian Pheasants Nest Formation. The rocks here sit right in the firing line of salt spray, wind and sunshine. Over time, salty water from the ocean soaks into tiny cracks and pores in the rock. When the water dries up, salt crystals are left behind. As those crystals grow, they push the sand grains apart, slowly breaking the rock down. This natural process is called salt weathering, or haloclasty.
You can see the effects all around this platform. Some areas look rough and pitted, others have thin flakes peeling away or a white, powdery coating of salt. It’s an ongoing process that shapes the rock a little more every day.
What Is Salt Weathering?
Salt weathering happens when seawater gets into the pores of the rock. As the water evaporates, the salt starts to form crystals. These crystals take up more space than the water did, putting pressure on the rock from the inside. Eventually, small grains loosen, flakes lift off, and the surface becomes rough and crumbly.
Because the sandstone here is quite porous and always exposed to sea spray, Bellambi Point is a perfect place to see salt weathering up close.
Why Bellambi Point?
Bellambi Point has everything needed for this process: constant salt spray, strong sunlight to help evaporation, and porous sandstone full of tiny spaces for saltwater to soak into. Each day, the rocks are wet and dry several times over, giving the salt plenty of chances to grow and expand.
This is different from thermal weathering, which happens when rocks expand and contract from heat and cold. Here, the main cause of change is the growth of salt crystals, not temperature.
Logging Tasks
Answer the following questions by observing the rocks at Bellambi Point. Please message or email your answers within two weeks of logging your find.
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Pitting: Find an area where the rock surface looks pitted or rough. Describe what you see. Are the holes small or large? Does the surface feel gritty or crumbly?
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Wet vs Dry Areas: Compare a spot closer to the water with a drier spot further back. Which one looks more weathered? How does repeated wetting and drying affect the rock?
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Explain the Process: In your own words, explain how salt causes sandstone to break down at Bellambi Point.
Logging Instructions
Take a photo with Bellambi sign in background.
Please send your answers via email or Geocaching Messenger within 10 to 14 days.
Logs may be deleted if answers are not received.
References:
"Physical Geology" by Stephen Marshak. Available at: https://www.wiley.com
"Geology of Australia" by David G. Roberts & S. Ian Smith. Available at: https://www.cambridge.org
"Weathering and Erosion" by the Geological Society of America. Available at: https://www.geosociety.org
"Geology of the Illawarra Region" by Paul E. V. Williams, University of Wollongong. Available at: https://ro.uow.edu.au