Saturday, 17 November 2007

Beyond the bend

The absence of the Artemis website and GPS tracker today makes posting just a little harder. However, as there really is only one road crossing the Nullarbor, it doesn't take a genius to work out where Mark has gone today. Assuming that he made it to the end of the longest straight yesterday, he probably overnighted at or near to the roadhouse at Caiguna..... The image is borrowed from Google Earth and shows the Caiguna roadhouse and the first slight deviation from the 90 mile straight. And here are part of the extensive facilities!

As I am saying so often on this geographical journey, it really is a 'voyage' of discovery for me and one of the facts I've learned in the last couple of days is that the Nullarbor is the largest expanse of limestone in the world. Having just completed a few lessons on limestone with senior pupils in school and having visited the limestone features in Yorkshire last weekend, it is strangely coincidental that I should now be reading so much about limestone in Australia. Limestone is a rock which is subject to chemical (mainly solutional) weathering. Although rain is scarce in this part of Australia, when it falls, it goes to ground down joints and along bedding planes in the rock. As rainwater is a very dilute form of carbonic acid, over time this will dissolve these lines of weakness in the limestone creating passageways and underground cave systems. And it seems that when it comes to caves, the Nullarbor has some of the largest (of which more shortly).

Near Caiguna, however, there are many blowholes such as this one (formed by rainwater dissolving its way into the ground) and here the explanation of why they are called blowholes....the name blow hole refers to the fact that these natural features breathe air in and out as high and low pressure weather systems pass accross the Nullarbor. The periodic reversal of air flows is a result of pressure equalisation between the underground caverns and the above ground air pressure.

Some 64km east of Caiguna on the Eyre Highway is Cocklebiddy where I am reckoning Mark had his morning coffee! If you follow the link, it leads to some interesting information about the area. Remember when you learned about those Australian sheep stations which were as big as Europe....... well, this is where they are! According to the info I have just read ....Cocklebiddy lies on the southern edge of Western Australia's truly vast sheep grazing belt. Within the area are several large scale sheep grazing operations, some larger than a number of European countries. One such station is Arubiddy which spans an area over 3200 square kilometres. With limited rainfall sparse stocking rates of about 8 to 10 sheep per square kilometre are the norm. And here, after a lot of searching, is Arubiddy itself..Learning about sheep stations in Australia when I was at school was definitely not what ignited my passion for Geography. However, I am thinking how much more interesting sheep stations could be these days with access to a real one like this, courtesy of Google Earth.

Sheep stations apart, Cocklebiddy's other claim to fame are the vast limestone caverns which underlie the area. 90m below the Nullarbor saline lakes occupy endless cave systems ....In 1983 a French caving expedition created caving history by exploring Cocklebiddy Cave to an unprecedented distance of 6.4 kilometres. This record was later broken in 1995 by an Australian named Christopher Brown - bettering the 1983 record by a mere 20 metres. Cocklebiddy cave system is unique in that the cave system extensively penetrates an aquifer that lies 90 metres below the Nullarbor Plain. Within Cocklebiddy cave are a number of vast limestone caverns, rockfalls and saline subterranean lakes that extend for several hundred metres. Amazing to think that all that water lies beneath the Nullarbor!

And finally, yesterday we did the 90 mile straight in a 2CV. Today, here is the view from a road train crossing the Nullarbor.....

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