Saturday, October 06, 2012

The Granites of Girraween

"As hard as granite." It's a saying so common it's almost a cliche. Granite's a hard rock, made of large, interlocking crystals. Granite bodies form when hot material from deep in the Earth's interior melts the underside of the crust. The semi-liquid mass of minerals rises into the overlying crust and cools slowly, over millions of years. When erosion wipes away the weaker host rock, the granite is left. Granite can form mountain ranges.

But over time, even granite is worn by water and ice. The minerals decompose, and with little cement between the crystals, the rock flakes away.

The southeasternmost portion of Queensland is called, with typical Australian directness, the Granite Belt. The granite was formed in the Triassic, and was first uncovered in the Jurassic. It's been slowly rising and being eroded ever since, and so the landscape we see today is in truth an ancient one. However, despite the long period of erosion, the rolling landscape is still about a kilometre above sea level. As a result the climate is typically hot in summer and cold in winter. The native vegetation is adapted to the conditions, and European settlers quickly saw the potential of the area for fruit and wine production. The Granite Belt's valleys are famous for their vineyards and orchards, but granite forms poor soils, and so large swathes of hillside are entirely bare, like ribs poking through the skin. I've just spent a few days walking around Girraween National Park, admiring the geology, the landscapes and, not least, some of the local Shiraz.

The rock in question - granite. This granite is composed mainly of quartz, pink and white feldspar, and black biotite.

Spring means wildflowers, and Girraween means 'place of flowers'. They're not big and bold, but the pink, white, purple and yellow flowering shrubs added touches of colour to the Australian bush. And the sound of bees!

The first big balancing rock had me grabbing for my camera before it fell over. By the time I'd seen a few hundred more, they didn't seem so remarkable. The boulders have been left as the surrounding granite flaked away along planes of weakness. Eventually they do roll downhill, but it's a rare event.

The Pyramid is one of the most fun climbs in Girraween National Park. It's not high, but the final stretch is steeeeeep.

The view from the base of the exposed rock face.

About halfway up, looking east. And no, the camera is not on its side!

A dyke crosses the face of the Pyramid, a good place to stop and catch your breath.

And when you get to the top, you can see the Second Pyramid. It's not climbable without rock-climbing experience.

Balancing Rock, on the peak of the Pyramid.

And more boulders, seemingly perched ready to roll off the Pyramid into the valley. Not today, though.

A Cunningham's Skink, enjoying the view, or the sun. He didn't say.

The next walk was to a formation called the Sphinx. I thought it looked like a koala, but Koala Rock doesn't have the same ring.

Someone's made a pretty decent sleeping platform at the base of the Sphinx. No idea how old it is - could be last week, or hundreds of years ago.

You think of underground streams being cut through limestone, but here, a stream has managed to undercut a granite bluff. You can hear the water but only see glimpses through the cracks.

Another dyke, this one above the Underground Stream.

The longest walk I did was up Mt Norman, down the far side and along a firebreak to Underground Stream. This is the northern face of Mt Norman, showing how the topsoil has been washed from the smooth face of the rock.

There's a good little campground tucked into the boulders beside the peak of Mt Norman. Here's the chimney.

 And this is the southern face of Mt Norman. It's quite a walk to see this, but that meant I had it all to myself. I did the main walks in Girraween, and plan to go back and explore more of the park.

Just for fun, a 360 view from the Pyramid.


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