I've kept this blog, on and off, since 2006. In 2015 I used it to chart daily encounters, images, thoughts and feelings about volcanic basalt/bluestone in Melbourne and Victoria, especially in the first part of the year. I plan to write a book provisionally titled Bluestone: An Emotional History, about human uses of and feelings for bluestone. But I am also working on quite a few other projects and a big grant application, especially now I am on research leave. I'm working mostly from home, then, for six months, and will need online sociability for company!

Tuesday, March 10, 2015

My Year with Bluestone: Au Natural

Today we move away from the examples of built and re-built bluestone to focus back on the arrival of bluestone in Melbourne, along volcanic basalt flows, past my house, along the Merri Creek, down towards the junction with the Yarra river.

This is the more geological aspect of my project where I am most outside my comfort zone, and where it is convenient to remind myself that this blog is a place-holder for some more sustained research in second semester.

Some of the geological sites and books I have started to look at were very difficult to understand, so I am delighted to discover the website of the Merri Creek Management Committee, a body formed in 1989 to protect and manage this vulnerable waterway (lined with industrial sites and subject to heavy erosion by the planting of European trees: truly, I wept when the willow trees were removed, but I'm over that now and glad to see more and more birdlife coming back to the creek).

I was going to post just my two pictures of basalt piles along the Creek in Clifton Hill,

but then found this site with its own pictures and analysis of what we are seeing here, though I confess I can't quite match up my images with theirs of Sites No. 3 and No. 6 (there are at least 45 listed on their website). Here's a paragraph of geological description: I need to find out more about "vescicles" and also need to go back and find ... the Cave!!

The principal feature is a very clear exposure of at least two lava flows or flow units that form a vertical cliff face adjacent to the low level crossing of the Merri Creek by the Merri Path at the west of Creek Parade, The lowermost sections of the flows exposed are at creek level 30 metres east of the low bridge on the Merri Path. This flow is ropy with many large aligned vesicles and probably represents a thin cooling flow unit (or several units) with rapid gas escape forming aligned and elongated gas bubble holes. The flow is well exposed as it is frequently washed clean of weathered debris by floods in the Merri Creek. Overlying this and well exposed adjacent to the bridge is a massive non-ropy lava flow with complex jointing and weathering features. The lower 3 metres of the flow has persistent vertical joints with a spacing of 40 cm to 50 cm giving a distinct columnar form. Closely spaced but irregular horizontal joints divide the columns into angular sub-blocks. Overlying the columnar section with a disjunct boundary, the upper part of the flow has disorganised jointing giving an irregular fractured surface

The websites also register concern about graffiti and souveniring from the sites: people do seem to want their own little bit of bluestone, even if it means putting the natural site at risk.

No comments: