Friday, December 28, 2012

Great Southern Land (Part 2)

The first National Park I wanted to check out was Warrumbungle National Park, near the New South Wales town of Coonabarabran. And right on the park border is the Siding Spring Observatory. As a life-long geek, I had to check it out. One telescope at Siding Spring, the Anglo-Australian Telescope, has a viewing gallery where you can see a state-of-the-art instrument that's discovered planets, observed far-off galaxies and watched the birth and death of stars. Siding Spring also has a great information centre and gift shop, and while I tried to keep my hands in my pockets, I ended up buying a telescope! The next few nights were spent spying the moon, Jupiter and its moons, various stars and nebulae - outback Australia has wonderfully dark skies, as spectacular as the countryside itself.

And so to Warrumbungle National Park. The Warrumbungles, as they're commonly referred to, are a range of eroded volcanic deposits. When most people think of volcanoes, they think of Mt Fuji-like towering peaks. Australia's volcanoes, on the other hand, tend to be formed by basaltic hot spots in the crust. Instead of tall, conical shapes, basaltic volcanoes form broad 'shield' shapes. 

Many of the Warrumbungle walks are up and along a range known as the Grand High Tops. It's a cool name, and the views lived up to the billing. During the climb up, the first rocks seen in the creek beds and track cutting are the sandstones that existed before the volcanoes sprouted from the plains. The overlying volcanic rocks include solid and bubbly basalt, often exposed in cliffs. Tuff layers, from deposited, solidifed ash, show up as softer layers in the cliffs. Tuff sometimes has cliffs eroded into it by wind and water.

Volcanic breccias are common. They're caused when debris flows down the sides of the volcanoes pick up rocks and boulders, and redeposit them further down the mountain. It's a violent process, and the rock fragments end up in an unsorted mess.

The dykes and plugs are made of a rock called Trachyte. It's chemically the same as the basalt, but it cooled and solidified within the mountain instead of being erupted. Because it cooled more slowly the crystals are larger, and the rock is harder.

From the top, you can see how the Warrumbungles rise from the flat plains of central NSW. To the north, west and south, it's flat as far as the eye can see.

The most distinctive peak in the Grand High Tops is 'The Breadknife'. It is the coolest dyke I've ever seen.

On the last day, I trudged up is Mt Exmouth. At 1200m it's the highest point in the National Park, and the 360 degree views made the climb very worthwhile.

The view from Mt Exmouth, looking east towards the Grand High Tops.

A panorama from Mt Exmouth.

The Arch, near Mt Exmouth.

I'd like to go back to the Warrumbungles, but may choose a time when the weather's cooled off a bit. Each day was fine and sunny, with temperatures of 35 - 38C. Each day I drank as much water as possible before setting out, and carried two litres with me. And each day, I drank it all and was looking forward to an iceblock at the Visitor's Centre when I got back! 


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