Sunday, 25 November 2007

Near Catastrophe

Don't worry - all will become clear shortly!

As I type, Mark is hopefully tucked up for the night at Tumby Bay on the east coast of the Eyre peninsula...
...having cycled to almost the tip of the peninsula and then turned north at Port Lincoln. I am hoping therefore that for at least part of the day, those troublesome southeasterlies might have been less head on. One of the problems at this time of the year in south Australia is that the southward shift of pressure belts and winds (as explained previously) will bring winds from the south east across the continent. However, added to that is the daily microclimatic effect when the land heats up and air above it rises. This 'pulls' winds in from the sea. This will become more pronounced as the day progresses and probably explains why Mark has been commenting on the much slacker winds in the morning.
I have mentioned the problem of salinisation in Australia in a couple postings and this morning again today Mark passed by another of those shallow salt lakes which stand out so starkly on the aerial photos. This one is Lake Greenly and despite what the tracker says, I think it is more likely that Mark skirted it on the road!
By mid afternoon Mark had reached Port Lincoln (where the Google imagery is disappointingly low res) and at that point he was closest to the southern tip of the Eyre peninsula, which an atlas has revealed as 'Cape Catastrophe'. The detail here on Google Earth is stunning and goes a long way to explaining how it came by its name....
The cliffs, battered by waves from the Southern Ocean are clearly treacherous. The inlets are called 'geos' and have been deeply eroded by wave erosion along joints and cracks in the cliff face. The promontory earned its name back in 1802 when 8 seamen were lost when Flinders, who was exploring the coastline of south Australia, sent a small boat ashore to fetch freshwater. There is a poignant account here of what happened.
Port Lincoln was also named by Flinders after the city from which he originated with the addition of 'port' in recognition of its excellent harborage. Today Port Lincoln is the home port for Australia's largest commercial fishing fleet. Today, the seafront of Port Linclon is dominated by this vast grain handling facility. Apparently, though the low res imagery is too poor to pick it out from the air, Port Lincoln is the railhead for a narrow gauge railway network which brings wheat from a wide agricultural hinterland to the port.

As you can see from the aerial photo of the southern tip of the peninsula, the coastline is marked by a series of promontories and bays and I'm afraid I feel another lesson on coastlines coming on! You may recall that yesterday I explained how coves are formed on concordant coastlines. Today it's the turn of headlands and bays on discordant coastlines. As I couldn't find a nice simple diagram on the Internet, I've drawn one for you..... After turning north from Port Lincoln, Mark has been cycling a discordant coastline where the rocks meet the coastline at right angles. Differential erosion (which erodes soft rocks faster than hard ones) produces the capes and bays. And so, having avoided catastrophe, Mark made it to Tumby Bay... a 'seaside resorty' sort of place judging from this..

1 comment:

Anonymous said...

Woah! You must be tired Mark. Only another 3 legs of the journey to go!
Good Luck!