Derwent River: A Beautiful Geology

But Where Does the Beach Start, and Where Does it End?

beach near trywork

At first I thought I’d simply visit each sandy beach, but within the first few minutes of our initial walk at South Arm I’d scrapped that plan.  Beaches are not disconnected from their rocky platforms or the coastline that surrounds them; it’s not possible to see the whole magnificent geology by looking at grains of sand even though they say a lot.

I was also immediately confronted by the question about what makes a beach.  Bedrock geology occupies about 60% of the shoreline so there’s a lot of hard rock.  The remaining 40% of the coast comprise sandy beaches; some tiny, waveless coves, some long surf beaches, each with their own sandy signature.

On walks with the geologist, we got to talking about how beaches are made.  We’re a tiny island hammered by the Roaring Forties.  Weather passes through and clearly subscribes to the view that when visiting, more than three days and you stink like a fish.  The cold fronts run hasty circles around the Southern Ocean.  I’m glad to see one go, I’m enjoying the mellowness that confirms my belief that there’s no better place on earth to live than on this island, when goddamit, that warm weather is shoved out by another cold front arriving in a temper and I have to down traveller and reef, close windows and crank up the woodstove, add another layer of thermals before heading down to the marina.  But our beaches face every which way, so for each one exposed to the prevailing wind another provides a safe anchorage or a sheltered nook be you human, seal or seabird.

A ripple becomes a wave, the moon entices then releases the ocean making a yo-yo of the tides, currents wend their way through the oceans deep and deep below the layer we’re a part of, magma schmoozes through fissures and cracks melting all opposition, adding its power to the building and destruction of coastlines.   With humankind intent on weighing in, turning tropical our polar waters and usurping the earth building roles of rivulets and the like, we’re bringing the Holocene that nurtured us to a climactic close.

I went looking for a definition of a beach.  I found long, technical ones that sounded far too complex for me so I decided a beach was where there was enough sand that the word ‘beach’ popped into my head.  Still, I would have to become attuned to where a beach began or ended and was going to learn that it was no easy matter.

That’s why I’m glad I started with the Derwent River beaches.  I’d no sooner get home than uncertainty about what I’d noticed – or, more usually, failed to notice – would assail me and back I’d go.  I’d go back often just for the pleasure of revisiting or to take a friend to see what I had found.  I’d go back because I’d begun to doubt my point of view, wanted to confirm the beach’s perspective both literally and figuratively, and because, the way I see it, neither the beach nor I are different and neither are we the same each time we meet.

Percentages sourced from Short, A.D. 2006.  Beaches of the Tasmanian coast and islands.  Sydney University Press, Sydney.

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