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Two pillars, a lot of trees and not much else

April 2, 2013

By Barry Tucker

I’ve learnt not to take my eyes off the road while driving my van because it usually means the van heads off the road too. I’m glad I risked it on this occasion because I saw something I hadn’t noticed before.

About 10 kilometres north of Narooma, 40 metres north of the Whitaker’s Creek bridge and some 30 metres to the east of the Princes Highway, in the dense and wild bush, there’s something odd that I hadn’t noticed on the 20 or so previous passings of this spot.

Pillar4

I know you can see the Spotted Gum (Corymbia maculata), but can you see the thick columns of rock to the left and right of the tree? These columns could be composed of granite, but I think they are volcanic flutes.

They are not easy to see clearly. And unfortunately when the pictures are enlarged the detail becomes very fuzzy. The pillars are on rising ground, on the side of a small hill or ridge. Their tops are rounded by abrasion.

Pillar7

The reason for thinking they may be volcanic in origin is that the Eurobodalla Shire contains a lot of evidence of ancient volcanic activity. The hill behind the pillars may be the remains of the volcano’s peak.

The side road into this property is blocked by a triple-padlocked gate. Signs on the gate say it’s private property and a hard hat area. The creek is crossed via a substantial bridge formed of hollow concrete blocks. I’ve got no idea what goes on at the end of the road.

Pillar1

Pillar3

Pillar5

Never mind the pillar, look at the creek — the water is muddy. Don’t know why. It hasn’t rained here for several days.

SideVent

Note the side vent and parasitic cone on the right-hand side of the diagram. I’m speculating that these pillars were vents that led from the main conduit of a volcano. They are not necessarily near the top of the volcano. Mount Dromedary (Gulaga), about 40 kilometres south, was 3,000 metres high when it was an active volcano. Today it is about 800 metres high.

IMG_0699

In the distance, beyond Narooma, Mount Dromedary (Gulaga). Narooma was originally known as Noorooma, an Aboriginal word for clear blue water.

LittleDromedary

Little Dromedary (Najanuga), only a few kilometres east of Mount Dromedary and closer to the coast, is thought to be the solidified core of another volcano. Notice the ripples in the foreground. The hill is collapsing towards the highway.

The Montague Island Nature Reserve, 11 kilometres off the coast of Narooma, is also thought to be volcanic in origin.

IMG_0727

Strange zigzag pattern of layered black rock sandwiched between a lighter coloured material. This is the southern end of Cemetery Beach, just south of Narooma. The zigzag pattern was formed when the molten rock either was forced to detour around a harder substance, or this area was raised again after collapsing, and squeezed. But how does the layering come about, and why are the layers of relatively even thickness?

Further north, at Tomakin, just south of Bateman’s Bay, there’s a large area of exposed basalt ridges running along the beach. These appear to be successive layers that have been heaved from the horizontal to the vertical position. The geological forces involved, the movement of water, sand, earth and rock and all the side effects are impossible to imagine.

Geology students from the University of Wollongong visit the Far South Coast of New South Wales to study its strange rock formations, especially on our dozens of largely untouched beaches.

In the Hole

Near the entrance to Wagonga Inlet, Narooma, rocks that have been raised, compressed, reshaped and eroded by the pulverising action of waves and the abrasion of sand and small rocks. There’s more zigzagging and other types of layering in this area.

The “not much else” in the headline refers to the lack of geological detail. If I can find out more about the origins of the two pillars in the bush I will have to rewrite my story.

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