Monday, 20 April 2015

20 April 2015: The Pinnacles, WA

20 April 2015: The Pinnacles, WA 
We took the Indian Ocean Drive north from Perth, to Cervantes. Spent a couple of hours in Nambung National Park, stopping to wander through the spectacular Pinnacles. 

The Pinnacles are limestone formations; the raw material came from seashells in an earlier era that was rich in marine life. These shells were broken down into lime-rich sands that were blown inland to form high mobile dunes. 

The manner in which such raw materials formed the Pinnacles is the subject of debate and three theories are proposed:
·         (1) They were formed as dissolutional remnants of a period of extensive solutional weathering (karstification). Focused solution initially formed small solutional depressions, mainly solution pipes, which were progressively enlarged over time. Some pinnacles represent cemented void infills (microbialites and/or re-deposited sand), which are more resistant to erosion.
·         (2) They were formed through the preservation of tree casts buried in coastal aeolianites, where roots became groundwater conduits, resulting in the precipitation of indurated (hard) calcrete. Subsequent wind erosion of the aeolianite then exposed the calcrete pillars.
·         (3) On the basis of “root casts” in other parts of the world, the third proposal suggests that plants played an active role. As transpiration drew water through the soil to the roots, nutrients and other dissolved minerals flowed toward the root 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 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. (courtesy Wikipedia)
     We discovered to our dismay that good rains in this part of WA to date have not only produced green vegetation along the coastline, but also hatched a plague of the most annoying flies ever! As we drove on through Leeman, Port Denison, and past Geraldton, 
     we were on the urgent hunt for fly-proof hat nets....


From Red Bluff lookout


Stopped overnight at Kalbarri. Fueled up and had to scrub the windscreen and front of the hire car vigorously to remove the hundreds of dead insects. Located two hat nets at the local supermarket to assist in managing the flies - they said this was their third shipment @600 nets a time! Drove along Kalbarri’s shorelines, stopping to walk and admire the evening views, flora and fauna of Pot Alley, Mushroom Rock, and Red Bluff.

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