Tag Archives: Geology

Coober Pedy – Life Underground

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Monday 26 August 2024 – Today was our last full day on the Ghan, and our final excursion, to a far away place with a strange-sounding name – Coober Pedy (pronounced “Peedy”). It was an exceedingly content-rich day; in other words this is a long post warning. I recommend you get yourself a cuppa or a glass of something stronger and settle down to read about the day.

After our stop at Alice and moving on overnight, the landscape had changed markedly.

We pulled into Manguri,

which was just a halt, really – no actual station or anything; just a gathering point so that people could hop on to the relevant coach for their chosen excursion. It was noticeable at this point that the temperature had dropped significantly now that we were moving south; it was very pleasant, in the low 20s, and a nice change from the 30+ temperatures we’d had further north.

We were booked on a general “explore Coober Pedy” tour, and I have to say I had no idea what to expect; all I knew was that it was the centre of a significant mining industry. The industry in question, or the quest which caused a lot of industry, is opals, and it’s a very significant one – Coober Pedy is estimate to produce around three-quarters of the world’s opal supply.

It turns out that mining opals is akin to gambling.  It’s not quite the same; gamblers always lose, the only winner being whichever house provides the game. In opal mining, it’s possible to win big or lose everything; apparently there’s a phenomenon called “opal fever”, where miners simply get addicted to the search for the next big opal seam. The trouble is that there’s no certain way of locating a seam of opal-bearing rock except simply to dig a hole and start looking around. It was not long after our coach set out (on a dirt road for much of the way) that we saw the first evidence of what effect this speculative hole digging actually has on the landscape.

Every single one of those heaps of rock, which are called “mullock heaps”, marks the presence of a hole that someone has dug in search of opals. They are everywhere on the landscape.

Apparently, even if nothing is found, the holes are not filled in with the mullock that’s been excavated, as this would result in unstable and unsafe terrain; so the holes just remain there, with a heap of mullock beside each one.

Some digging obviously uncovers rich seams which get expanded as they’re explored,

and some appear sufficiently promising that drills are set up to explore further

with blowers to clear the excavated dust away – drill on the left above, blower on the right,

and a blower in action above.

There are two main types of drills – small-bore ones for initial exploration, and larger-bore for creating a main hole from which tunnels can radiate out in the search for these precious mineral creations.

The process of claiming territory to mine is quite straightforward, but the manner of extracting opals is delicate and precise as opal is a fragile material; it doesn’t lend itself to industrial-scale large mining machinery, which is why the landscape is dotted with holes and heaps. Anyone can basically dig a hole anywhere for initial exploration. If such exploration yields a sufficiently good prospect of finding opal seams among the rock, then a (renewable) claim can be lodged (and paid for) for a certain area around the hole and for a certain period of time – maybe 20 metres for three months – and the person who lodged that claim puts pegs to mark the claimed area. They are then not allowed to move the pegs or to lodge another claim until the expiration of the current one, which puts a stop to people making multiple explorations. And there’s absolutely no guarantee that an exploration will find opals – it’s entirely a gamble.

The base rock in which opals form is sandstone. Water, seeping into the ground, picks up silica from the sandstone and then settles into cracks and other voids in the stone. Over millions of years, the water evaporates, leaving behind deposits of silica spheres; if these spherical silica deposits are arranged neatly in a uniform lattice arrangement, the interference and diffraction of light between the layers creates the colours which mark out a valuable opal; if irregular, then the result is called “podge” and is not particularly valuable. Extracting opal from rock requires extreme care – if an opal is cracked it loses all its value, so it is basically a manual operation, which explains why the good stones are so expensive.

The landscape this extraordinary industry produces is unique and strange.

You’ll notice that the landscape is utterly devoid of trees, which means that early settlers and miners were a tad short of the usual materials for building houses. The solution was direct and simple – to build dwellings underground. The stone is soft enough to make excavation easy, and yet firm enough not to collapse; the resulting dwellings (like cave dwellings everywhere, of course) are stable in temperature throughout the year, which is good, since outside it can be anything from below freezing up to 50°C. We got a chance to see what an underground house looked like later on in the day, but there were a few other things to look at first.

Our driver, Jason, described the terrain, as he drove us towards a particular viewpoint, as having once been seabed. Clearly, the waters had receded, and when they did, a remarkable process of erosion began, and what was seabed was worn further away in some places but not in others. This left some significant outcrops of stone which appeared to have “broken away” from the rest of the landscape. Actually, they were just remaining bits of seabed, but their appearance was such that they re called

The Breakaways. It’s an extraordinary landscape.

Having admired this amazing vista for a while, we headed back to Coober Pedy. The houses there are not all underground dwellings. Some are perfectly normal houses

and some are sort of hybrid, with some areas above ground and some below.

Underground houses are marked by ventilation shafts

which you can see sticking up above ground here – clearly, there’s a need to get fresh  air circulating around the dwelling.

It’s not just housing that has gone underground; so has worship.  The town features two underground churches.  We were taken as a group to the first one, a Serbian Orthodox church, which is built into a hillside.

Inside, one can see, by looking at the roof and walls, that it’s been created by two types of drilling machine – square and round.

It’s an attractive interior

Jane and I also visited the Catholic Church in the town.

In between visiting the two churches, we had an underground lunch

which was served up in the excavated but no longer active areas of an opal mine that was still in use.  We had a quick tour before sitting down to lunch,

where one could “noodle” (sort through loose stones in search of opals) or “pick” – chip away at the rock.

Whichever method one chose, a useful implement to have to hand was a “black light”, i.e. an ultra-violet light, whose beam illustrated the presence of opals within the rock.

This was technology not available to the original settler miners. Apparently what they did was to drill until they heard the sound of glass being broken, which meant that they’d found some kind of a seam, and then proceed by hand.

Outside the lunch location was some machinery which showed that the mine was still active.

as well as an exhibit of an old-fashioned windlass, which would once have been used to hoist up excavated rock.

The final component of the day was to visit a combined opal museum and underground dwelling.

Our time there started with a short lecture about the different sorts of opals (doublets, triplets, etc) and how they’re produced, with careful polishing to bring out the colours. Then we were shown round the underground dwelling which is part of the operation. It really is just this house, you know? but with no windows.

The first three pictures below are of a section excavated in the 1920s and inhabited by a miner; the remaining pictures are of the modern extensions!

Some people professed themselves uncomfortable with the idea of sleeping in the bedroom, which could, of course, be utterly and absolutely black and carry with it the extreme risk of barking your shins or banging your head during any nocturnal wanderings. I think it would be great, provided there was just a tiny bit of illumination.

There was, of course, a retail opportunity.

Outside, one could wander up on to what was effectively to roof of the house – you can see the ventilation shafts.

Its location gave a good view over the town of Coober Pedy.

The town’s location and unique geology have made it a great location for films where utter desolation is needed (e.g. Mad Max), to the extent that the town has erected its own version of the Hollywood sign.

Wandering about, one can see that there is merciless merchandising of the underground theme.

Sadly, we didn’t have time to get to the underground bar before we had to go back to the train. En route, Jason and the other coach drivers stopped short of the train in a location which enabled people to take a shot of its entire length,

and was, of course, the location for a feeding frenzy of selfies.

We arrived back at the correct side of the train to find that the crew had set up drinks and canapes outside

which one optimist used as the venue to propose to his girlfriend.

(She said “yes”, apparently.)

And so ended an exceedingly unusual, interesting and enjoyable day, full of strange landscapes and bizarre life choices. The morrow would see us arrive into Adelaide and the end of our journey on the Ghan, so stop by these pages to see what happened when we arrived.

Ayers and Graces

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Sunday August 25 2024 – Before we could get to today’s keenly-awaited excursion, we had to deal with the non-trivial matters of getting up, showered and dressed within the confines of our small cabin. Although it required some fairly precise choreography between the two of us in order not to be bumping into each other all the time, it was (for me, at least) much less awkward than I had been fearing.  The bathroom area in our little cabin is small, but very well-organised, and doing the morning’s ablutions was remarkably trouble-free. I was also quite surprised to have slept reasonably well; my last experience on a sleeper was from London to Edinburgh and it was ghastly – noisy, uneven and uncomfortable. The Ghan was rather noisy at times – there was what felt like shunting done during the night, leading to lots of creaking and groaning, some of it on my part; and it was accompanied by a certain amount of lurching (the carriage, not me), but throughout all that we both managed to grab a reasonable amount of sleep.

We got a good breakfast, swiftly and competently served by the crew, who really work hard and do a good job; our section manager was a lass called Esther, who, as well as helping dish out the meals, was excellent at ensuring that we knew where we had to be and when, and that we had the right bits of identification card on our “Look At Me, I’m A Tourist!” lanyards.

I have had a great and abiding love of aerial photography, having had the excitement of my first views from an aeroplane at the age of nine. (Hence, on this trip I’ve been lugging around with me a drone which I haven’t really had a chance to use yet.) This love of aerial photography means that today’s excursion is one which I’ve been looking forward to with considerable excitement. First, we had to get to Alice Springs (or Mparntwe, as it’s known to its indigenous owners), through countryside of a type which was really rather familiar by now – scrubby and burnt in places.

At about 11.30am we pulled in,

and, as is standard in large-scale tourist activities everywhere, were sorted into buses to take passengers onward to their various activities for the day. Our bus was driven by the usual bluff Australian chap, in this case called Gerry, who was good enough to take us up to a viewpoint so we could take in A Town Called Alice (see what I did there?).

The viewpoint has a complicated aboriginal name

but we know it as Anzac Hill, which leads to the War Memorial.

On the way up, signs remind visitors of the many contributions to the war efforts of the 20th and 21st centuries made by solders from Australia and New Zealand, from WWI through to Iraq.

The lookout offers a great set of views over Alice Springs.

The gap above is where the road south leads out of town. This is the Stuart Highway, the longest road in Australia, which has been with us since Darwin and will still be with us after some 2,700km as we reach Port Augusta, just 300km short of Adelaide, the ultimate destination of this train ride.

Apparently, property prices in Alice are very high despite its rather remote location. This is because it can’t expand any further without infringing on indigenous land or cattle stations.

On the way down from the lookout, the backs of the commemorative signs are also decorated with reminders of the various conflicts.

Gerry also drove us around Alice to get a view of the place. It’s unremarkable  – just this town, you know? – and it’s kind of difficult to capture the feel of a place from a moving coach, but it does have (at least) a couple of striking murals.

Slightly frustratingly (because I wanted to get on with the day’s main activity), we had to have lunch first; this was served to the Ghan’s passengers at a place called Madigans.

It’s worth mentioning that the stewards from the train were part of the service, so their responsibilities carry on even off the train; they really do earn their corn.

And then – at last! – we were off on our excursion proper.  Here is a clue as to what we were about to do.

It’s a Cessna 208 Super Caravan, an aeroplane with which we first became familiar in Madagascar as we flew north to Anjajavy. Two of these aircraft awaited the group of 12 undertaking today’s flights, and there was a ripple of amusement as one lady, who was maybe one egg short of a clutch, couldn’t get to grips with the idea of a caravan being anything other than something you go camping in.

It was interesting to see the GABA (Great Australian Bugger All) from above,

though the landscape was actually very varied and interesting.

It included Pine Gap, the local US spy base near Alice,

and a not-inconsiderable bush fire

whose smoke affected the view across some salt flats.

After about an hour in the air, though, we caught the first sight of the reason we’d undertaken this 90-minute flight.

Yes, there it is, top right.

Uluru, or Ayers Rock in the old language. The pilot made sure that each side of the plane had a good view of this remarkable lump of masonry, which has a variety of aspects, depending on the angle of view.

It is, of course, an iconic part of the Australian landscape, and a considerable tourist magnet, as shown by the size of the local airstrip

and the number and variety of accommodation opportunities in the vicinity, such as this – another one which looks suspiciously like camping.

What we hadn’t known about beforehand was another remarkable rock formation quite close by Uluru, which we also flew by for a look –

The Olgas, or Kata Tjuṯa in the local indigenous language. There are 36 domes in this extraordinary formation.

The day’s aerial excitement wasn’t over, either. We landed at Ayers Rock airport to refuel and took off once again

to fly back to Alice, but we took a slightly different route back, over another fantastic formation called King’s Canyon – another local landmark which we hadn’t known about before today.

Apparently, one can go walking around the canyon, which sounds like a very interesting way of passing a morning.

By this time, the sun was going down, and the angle of the light really highlighted the considerable amount of geology that goes on in the area.

Among all of this huge landscape, one could spot the occasional outpost of civilisation

and looking at it in its greater context, one could only wonder

Why? Why there? What’s going on?

The ride back was actually more interesting than the ride out, but eventually it was time to land back at Alice

and be taken to our evening meal, which was at the Alice Springs Telegraph Station, the original site of the first European settlement in central Australia, one of twelve stations along the Overland Telegraph Line.

It was billed as “dinner under the stars”

which was fine in theory, but somewhat overshadowed by the clouds which cropped up and made seeing the stars a bit tricky.  A chap called Tom tried to show us some of the local astral geography, but it required a certain feat of imagination to get much out of his undoubtedly enthusiastic efforts. There was also the possibility of a camel ride

and a band entertained us just loudly enough to make conversation difficult,

so we took the opportunity of the first bus back to the train in order take a rest after a memorable day. I know that seeing Uluru is something that practically every tourist visiting Australia will do, but our view of it today was a great pleasure; and to see the other formations in the area was, if anything, even more exciting.

We have one more day on the train, or, more accurately, largely off the train; tomorrow we spend much of the day visiting a place called Coober Pedy where life is largely underground for a variety of reasons. This is an intriguing prospect and one I hope you’ll return to these pages to find out more about.

 

 

 

 

 

 

 

 

 

 

 

 

 

Heading south through the “Top End”

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Saturday 24 August 2024 – After our short time in the area, it was time to leave Darwin and head southwards, aiming for Adelaide, some 2,600km away. To do this, we would cross the “Top End”, a rather vaguely- and informally-defined section, basically the northernmost bit of the Northern Territory. This was to be a train journey, but not just any old train; we were catching the Ghan.

As seems to be inevitable with these things, it involved an early start, so the alarm went off at 0500 so that we could take breakfast before checking out of the hotel and in for the train journey. Having taken breakfast, we noted that there was a special desk set up in the hotel lobby for the train, with people’s bags clearly waiting to be transferred. We chatted with the guy there and picked up our lanyards and went to get our cases.

The baggage aspect of this had been the subject of much planning and a certain amount of angst as we worked out our strategy. A strategy was necessitated by the fact that our accommodation on the train wouldn’t have room for our suitcases; we needed to check them in and keep a few essentials back for use during a three-day, three-night journey. We had brought special foldable bags for just this purpose and so we had spent a bit of time sorting these out yesterday evening.

Imagine our surprise, when we got back to the hotel lobby with our bags, to find that the chap, his desk and all the cases had vanished, and yet it was only 7am, well before our official pickup time. There followed a certain amount of agitated making of phone calls, and we eventually established that someone was on the way to pick us up.  In the end, a small bus with a luggage trailer turned up and ended up being our private transfer to the Darwin Convention Centre (which would only have been 4 minutes’ walk away) so that we could do the real check-in. The driver told us he was the “sweeper” as there was apparently a bit of confusion generally that morning!

There were a load of people sitting outside the convention centre

And, as it turned out, inside as well;

The blurb had promised “light refreshments” – in fact we could have taken a full breakfast here, had we known. We did manage some champagne disguised as orange juice…

After a few preliminary announcements, it was time to troop out to the coaches to take us to the train, which was actually a good way away.

We were introduced to our cabin,

which was actually a lot smaller than I had been expecting, to be honest. I still had memories of a Southern Orient Express journey we’d undertaken between Brisbane and Sydney over 20 years ago, which had actually offered accommodation with a double bed, whereas this was self-evidently a bunk-up, which is getting dangerously near to camping as far as I’m concerned. At least we had shower and toilet, which is much better than the original Simplon Orient Express, which was just the bunks plus handbasin, with shower and loo down the corridor,  when we did it a few years ago.

Still, we had a good location, right next to the bar

And the dining car.

A few words about the train itself. In 1878, work started on a planned 2900km railway link between Australia’s southern and northern shores. Starting at Port Augusta on the south coast, the narrow-gauge railway reached nearly 700 km away, at which point work stopped for 40 years, and the work of transporting people and materials northwards to Alice Springs was undertaken by camel trains, which were mainly operated by people from Afghanistan. It’s widely thought that the name “The Ghan” is derived from these hardy Afghans, though many other (mainly less charitable) versions of the derivation also exist, according to the Wiki entry. It wasn’t until 1929 that the railway reached as far as Alice Springs (1200 km from the start), and it took until 1980 for a standard gauge route to reach all the way north to Darwin.

Confusing the issue slightly is a locality somewhat south of Alice Springs called Ghan, which  also owes its name to the role played by the Afghans and their camels in opening up central Australia.

Our train was 750 metres long and had two engines and thirty-five carriages, which underlined the convenience of our carriage’s location; we might have had a long walk to the bar, and that would never do.

The train set off dead on time at 0900, and having had breakfast at our hotel first thing, and been offered breakfast at the convention centre, we were then called for 1015 brunch in the dining car, which was good food and very efficiently served. It’s clearly going to be difficult not to eat too much during the three days of this train trip.

The countryside that we passed as we left Darwin showed more evidence of the burning that we’d seen.

On each of the three days of the trip we had booked some kind of excursion, at least one of which should be jolly exciting (stay tuned for more…); today’s was a sedate cruise up the Katherine River, or Nitmiluk as it’s called in the local language.

Our stop was, unsurprisingly, at the city of Katherine, where there were kapok trees in flamboyant flower by the rail side,

and we embarked on a 30-minutes coach journey, driven by the ebullient Harry, to our cruise departure point. Harry was good enough to depart from his official route to show us a bridge across the river

which apparently had been under water in the extra-exciting flooding of 1998, giving one an idea of just how much water they can get here in the wet season.

Our cruise departure was slightly chaotic, as there was no-one to tell us where to go after we got off the coach, and a coterie of the leaders determinedly set off in what turned out to be the wrong direction. But eventually it became clear where we should be going and so we all trooped on to the boat for our cruise.

The lass in the pink hat was our driver and guide, and kept up a dryly witty running commentary about what we were seeing, educating us on crocodiles, particularly the difference between salties and freshies (should you fall in, one swims towards you, the other swims away) and the difference between a canyon and a gorge (the latter has a perpetual supply of running water), as well as some of the geology that was very obviously going on around us.

The scenery was striking, with some impressive cliffs and rock formations.

They do have crocodiles here, mainly freshies, which have various nesting sites on beaches along the river (salties lay eggs among rafts of sticks in the water, apparently).

Salties would kill and eat freshies, so great efforts are taken to remove the former should they end up here, which they can when the waters run high during wet season. Therefore, from the start of the dry season various tactics are used to detect and relocate them, with a clear period of six weeks with no sightings being the requirement for declaring the area clear of rogue salties.  One tactic is very simple – a buoy.

Salties, being curious creatures, will bite these to see if they are edible, and it’s the toothmarks that give away their presence and possibly even their size.

The Katherine River Gorge actually consists of 13 gorges, something which only becomes apparent during the dry season, when the waters recede and rocky barriers appear; in the wet, the waters are high enough that there is only one gorge apparent. We were here towards the end of dry season, so we eventually reached the dead end of the first gorge

and in order to carry on, we had to get out and walk about 500m to the next gorge along.

This walk led past some rock art, painted puzzlingly high up on a sheer rock face;

and one could see the water trickling down from the next gorge along.

We hopped on board a second boat

which took us past some more impressive slabs of masonry,

and some wonderful colours.

We pottered around this second gorge for about half an hour, admiring the scenery,

and then retraced our steps to await the boat to take us back through the first gorge,

which was driven by Johnny Depp, who’s obviously out of real work at the moment.

Right at the end of the cruise (which would also have been the start, but we weren’t told about this then) our lady skipper pointed out a specially-built viewpoint high up on the opposite bank.

If you examine the rock formation under it, it would appear to be balanced on the nose of a crocodile – a pleasing illusion. [ Crocodile Rock – ? Ed ]

A bus ride then took us back to the train,

our evening meal and a relatively early night, as we had to be ready for the morrow’s adventure, which was something that we’d both been greatly looking forward to. Exactly what it was is something you’ll have to find out about by keeping in touch with these pages.