Saturday, 27 August 2016

Caiguna Blowhole

I thought a blowhole was on a rocky cliff where ocean waves pressurise and erode a hole though to the surface inland just far enough that you could see ocean spray or hear the waves thumping through the cave.

But, I have been educated. There is a rest stop on the Eyre Highway where a small hole in the ground about 15km inland from the cliffs and waves along Great Australian Bight called Caiguna Blowhole.

Caiguna Blowhole
The Nullarbor is flat, it is huge and it is limestone. Cave systems throughout the Nullarbor have been formed for millennia by rainfall weathering even though it is one of the driest limestone areas in the world. Some of the caves have collapsed to form large depressions, some like Caiguna have just a vent leading to the surface. And all caves breathe due to air pressure. When air pressure is high the caves breathe out and when air pressure is low they breathe in.

When we were at Caiguna the cave was breathing out. the breeze was cool and strong so we tied a handkerchief onto a piece of cotton to demonstrate. Family visited the cave a few years ago on an extremely hot day and saw numerous birds flying in and out of the blowhole to take advantage of the cool air.

I also took the opportunity to photograph the plants around the carpark area. So, these are my final photos of our truncated trip to the west. (See previous blogpost.)

Emu Bush Eremophila sp.



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