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Our first outing - Cervantes back to Burns Beach

Day 4 - the return trip

sunny 24 °C
View Sam Smart in World War II & Back to Oz on SteveJD's travel map.

After a comfortable night's sleep, we decided to have a walk around Lake Thetis before heading for the Pinnacles and home. As with the last few days, the weather was fine and warm with little breeze, so the surface of the lake was quite still. The lake was not far from where we had stayed and had a variety of interesting wildflowers but the main focus is on the stromatolites which are found a short way along the walk. Stromatolites are 'living fossils', bulbous rocky lumps formed by the deposition of calcium by microbes which are a species of cyanobacteria. Fossils of stromatolites have been found in rocks dating back over 1 billion years, hence the 'living fossil' description. These strange objects are found in few places and in some locations are called thrombolites; the difference between the two is fine and technical and is not as significant as their mere existence (i.e., I do not really fully understand the difference, certainly not well enough to describe it!). The lake is shallow and the combination of this and the lack of wind made it possible to take some reasonable photos of the stromatolites. While approaching the stromatolites, we spotted a red-capped dotterel (or red-capped plover) which obliged us with some good poses. Both before and after seeing the stromatolites we saw a variety of wildflowers including several yellow tailflowers, new flowers for us.


Once we had completed our walk, we drove down the road about 15km to Nambung National Park, the primary attraction of which is the Pinnacles Desert. When we lived in WA, the general consensus was that the pinnacles had been formed by the accretion of limestone around ancient tree roots. However, on this visit we discovered that there are now different theories and I quote selectively from Wikipedia "..they formed as a result of a period of extensive solutional weathering...Focused solution initially formed small solutional depressions, mainly solution pipes, which were progressively enlarged over time resulting in the pinnacle topography."

Or another "..theory states that they were formed through the preservation of tree casts buried in coastal aeolianites [windblown sedimentation in English], where roots became groundwater conduits, resulting in the precipitation of..hard calcrete. Subsequent wind erosion of the aeolianite then revealed the calcrete pillars."

A third theory ".. suggests that plants played an active role in the creation of the Pinnacles, based on the mechanism that formed smaller “root casts” in other parts of the world. As transpiration drew water through the soil to the roots, nutrients and other dissolved minerals flowed toward the root—a process termed "mass-flow" that can result in the accumulation of nutrients at the surface of the root, if the nutrients arrive in quantities greater than that needed for plant growth. In coastal aeolian sands that consist of large amounts of calcium (derived from marine shells), the movement of water to the roots would drive the flow of calcium to the root surface. This calcium accumulates at high concentrations around the roots and over time is converted into a calcrete. When the roots die, the space occupied by the root is subsequently also filled with a carbonate material derived from the calcium in the former tissue of the roots, and possibly also from water leaching through the structures."

I think the second theory is the one with which we were familiar although perhaps in less scientific language. I still like this idea but have no scientific basis for my preference! The calcrete referred to is a form of limestone comprised of broken-down seashells "..from an earlier era that was rich in marine life.".

As we were coming to the end of the 4km drive around and through the Pinnacles Desert, we found a western grey kangaroo browsing on a parrotbush, unworried by passing cars.


As we drove from the Pinnacles towards Lancelin, we passed large areas which were thick with grass trees. The proper name for these is xanthorrhoea and one or more varieties grow in all Australian states and territories, other than the ACT. They used to be known as 'blackboys' as the plant and flowering stem were said to resemble an Aborigine standing with a spear. This is now politically incorrect so they are either called grass trees or balga (one of the Aboriginal names in WA) or, in South Australia, yakka, another Aboriginal name. The plants are slow growing but can live through fires, so many plants are hundreds of years old. As with many bush plants, the Aborigines have a number of uses for the flower shaft, nectar from the flowers and resin. Europeans also use the resin for a variety of purposes.


In Lancelin we stopped for drinks and a light snack before continuing homewards. Lancelin is a small town with the primary occupation being fishing and catching crayfish although it is becoming more popular with tourists, particularly as Perth continues to expand northwards. Lancelin was named after a French scientific writer when Captain Nicolas Baudin was exploring the area in 1801.

Posted by SteveJD 01:29 Archived in Australia

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Looks like you are having a wonderful time. So pleased that Steve is getting about now.

by Gillian Geraghty

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