This was one of our favourite beaches on our recent WA trip, it isn’t soft, it isn’t luxurious, it isn’t white but it’s pebbly and pink! Each little pebble has its on unique story to tell. Pebble beach was once mined for the pebbles on the beach but is now protected. Our aim with this particular Earth Cache is to take you to a beautiful spot and teach you some basics, we have presented this earth science lesson on a basic level to accommodate those who avoid EC’s ‘cos they are too hard’ and also to accommodate those travelling with Children (TAWKers) who incorporate Earth caches into their curriculum.
A short dirt access road to the beach with plenty of parking if you have a 4WD can drive on to and along the beach.
By definition a Pebble is a clast of rock with a particle size of 2 to 64 millimetres based on the Krumbein phi scale of sedimentology.
A beach composed chiefly of surface pebbles is commonly termed a shingle beach. This type of beach has armoring characteristics with respect to wave erosion, as well as ecological niches that provide habitat for animals and plants.
Pebbles can give Geologists and insight into their past, the size suggests how much energy was used to transport them, the texture suggests the amount of chemical weathering they have endured and the colour suggests the composition, indicating their possible original source and time spent in particular location.
The majority of Pebbles on the beach here at Exmouth have come from the nearby Cape Range. The simplified series of events that has led to this beautiful beach is as follows: The pebbles were originally much larger pieces of rock which due to weathering were broken from Cape Range. Further weathering and erosion has transported them into streams and finally into the bay.
The four erosional processes that enabled this to happen were:
- Hydraulic action this is the erosion that occurs when the motion of water against a rock surface produces mechanical weathering. Most generally, it is the ability of moving water (flowing or waves) to dislodge and transport rock particles.
- Abrasion is the mechanical scraping of a rock surface by friction between rocks and moving particles during their transport by wind, glacier, waves, gravity, running water or erosion. The intensity of abrasion depends on the hardness, concentration, velocity and mass of the moving particles.
- Attrition is a form of coastal or river erosion, when the bed load is eroded by itself and the bed. As rocks are transported downstream along a riverbed, the regular impacts between the grains themselves and between the grains and the bed cause them to be broken up into smaller fragments. This process also makes them rounder and smoother.
- Solution is the process in which acids contained in sea water will dissolve some types of rock.
To log this Earth Cache we require you to wander around and look at the area, consider the information given and perhaps if you need to do some research of your own, then message us with the following answers to the best of your ability;
1. Immerse yourself in the pebbles, sit down, enjoy them, run your hands through them, indulge your eyes and look at the interesting patterns and designs. Describe what you see and what do you find visually pleasing about them?
2. Do you find any curiosities or anomalies? Describe them.
3. Considering the information given and the chart below, where would you place the Pebble Beach Pebbles on this chart? What does that suggest about the length of time they have spent here?
4. At the marked reference point S 22° 02.513 E 114° 06.924, what Geological feature can you see here? Bonus points if you can correctly name it.
5. A photo of your team or GPS near GZ, we can't get enough of this place so upload as many photos as you like! (Optional) Source: Wikipedia, Exmouth.com.au
