Monday, 3 December 2007

Volcanoes and on to Victoria

It's a strange title but all will become clear... I hope! Firstly, however, it's probably time to take a broader view again to see exactly where in Australia Mark is. So, here is the 'big picture'..... Mark is now just over half way between Adelaide and Melbourne, having crossed the border between South Australia and the state of Victoria earlier today.
Victoria is the smallest state of mainland Australia (second smallest in the whole country after Tasmania) but it is the most densely populated and urbanised. 70% of its population live in Melbourne, the capital.

Marks' route today saw him cycle the last 50 kilometres of South Australia and then on about another 110 kms into Victoria to the town of Portland.

This morning he passed through Mount Gambier which is located beside a most interesting volcanic feature - a maar volcano. If I am honest, I can only very vaguely recall hearing of maar volcanoes. Basically a maar is a volcanic crater produced by the interaction of rising magma and groundwater. What happens is that the magma and water produce strong steam explosions that blast up through the surface. The result is a crater that may have very little of a built-up rim. Here is a closer view of the maar lakes at Mount Gambier ......The lakes are a major tourist attraction not least because of the fact that the water of the larger one (aptly named the Blue Lake) turns a vivid cobalt blue during the summer.
As the Wikipedia entry for the Blue Lake states, "The exact cause of this phenomenon is still a matter of conjecture". However the explanation given sounds convincing (if just because I can't claim to understand it!) There are also some other images of the 'blueness' including this one.

For much of the second half of the day Mark cycled through miles of commercial forestry (see yesterday's posting about Southern Pine fluff pulp) interspersed with agricultural terrain which has much evidence of salinisation.

By this evening he had reached Portland and was back to a small 'patch' of high res imagery. Mark has been to several locations in the last week or so which remind me of the Dorset coast... firstly there was the Cove at Elliston on the west side of the Eyre peninsula which was so like Lulworth, then there was the Coorong which was like Chesil beach and the Fleet lagoon and today there is the peninsula at Portland which is so like the Isle of Portland in both name and geography. Here's the Isle of Portland with Portland, Victoria for comparison......
...and just as Portland stone (limestone) has been quarried from Portland in Dorset, so limestone has been quarried from the peninsula at Portland in Australia.

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