Tag Archives: Geology

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.

 

 

Kimberley Day 3 – Talbot Bay and the Horizontal Falls

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If you’re not into the savage beauty of extraordinary rock formations, then there’s nothing here for you. Move on…

Oh, still here?  OK, then.

Thursday 15 August – Before anything else, some geological background to the Kimberley.

I’ll be honest, I didn’t know exactly what “The Kimberley” meant, except as the highly scenic destination for a lot of cruise ships. Courtesy of one of the onboard lectures, I have learnt a few basic geological nuggets.

  • Everyone knows that bits of the Earth’s surface have moved around; at one stage most of the land was in a single great mass which had since drifted apart.  What I learned is that Australia is not just one of these drifting land masses, but is actually composed of multiple cratons – micro-continents – which over the millennia have crashed into each other and got stuck together – “sutured” in geology-speak.
  • It’s a law of geology that rocks accrete vertically, oldest, therefore, at the bottom
  • When lumps of land collide, unsurprisingly the bits of land at the edges do not have an easy time of it, and compete for superiority. One edge “loses” and is either forced underneath the other, (a process called subduction) or over it (obduction).
  • The Kimberley is the verbal shorthand for the Kimberley Basin, a craton which collided with Australia and got stuck to it around two billion years ago.

So, you can see that the land round the edges of the Kimberly basin is going to be full of these subductions.

Still with me?  Oh, goody!

Today we had arrived at Talbot Bay, towards the left-hand edge of the Kimberley Basin. One would therefore expect the rock formations to be somewhat tortured by this subduction/obduction process.

One would be right.

Here is what the area looks like under the serene gaze of Google Maps.

Geologically, though, there’s a lot going on.

 

The land has been buckled and twisted in a very unusual way. Erosion has worked its way through the more easily weathered layers, thus exposing those underneath.

OK, so what? I hear you cry. Well, you get to see some rock layers that are normally buried under millions of years’ worth of other rock. More to the point, though, the landscape is visually arresting, particularly now I’ve set it up for you.

So, there now follows a large number of photos of rock formations.  You may care to leave at this point in the symposium, or, alternatively, to skip to the bottom where something slightly less dull happens.

We cruised around for a couple of hours, giving us a opportunity to take lots of photos.

I hope you can see the extraordinary angles the layers have been buckled to – some are almost vertical and others remarkably twisted and distorted.

This is my particular favourite – the colour of the rock just blazed from underneath the darkness.

The darkness in all of these images, in many cases just above the water line, is caused by cyanobacteria. These would normally be a blue green, but when exposed to the light they go into stasis and their colour changes to dark grey or black until they are covered by water as the tides go up and down.

Ah, yes. The tides.

The tides are the cause of a phenomenon that pulls in tourists from far and wide.  Some of them like us, would be in boats; others would take seaplane tours, from platforms rather unattractively parked in the middle of the bay.

What attracts them is the behaviour of the tidal currents through a couple of gaps in the rock, one of which

is sufficiently narrow to create whitewater rafting-style currents.

But not for us, sadly.

Once again, that old devil moon was spoiling our fun; we were here at neap tide, so the thrilling flood looked more like, well, a dribble, really. It may not have looked like much, but the guides attempted to make things more exciting for us by jockeying for position in the stream.

Had we been here at spring tide, this is how it might have looked.

Now you can see why it’s called the Horizontal Falls.

It is – at the moment – a popular tourist activity to race up through the channel.  Our Zodiacs did not, out of respect for the customs of the indigenous tribes, for whom this area, traditionally called Garaan-ngaddim, is a powerful, sacred place; their belief is that boats that pierce these gaps disturb Woongudd, the serpent who creates this wonder by gliding between the cliffs.

Others at the scene were less respectful.

This was a craft from the luxury cruising ship True North

which was in the area at the time.

The practice will fairly soon be banned. Out of respect for indigenous customs? Or because there was an accident a couple of years ago? Your call.

In any case, it was just as well that none of the passengers described in that accident fell into the water;

this was a very large crocodile which we spotted further up the bay.

As well as the croc, and a couple of crabs and mudskippers, which I totally failed to get decent pictures of, we saw a plant called the Kimberley Rose.

It’s a deciduous tree, also known as the Sticky Kurrajong, or Brachychiton viscidulus
to grown-up dendrologists.

The expedition wasn’t the dramatic thing it might have been at spring tide, but the area is beautiful and the rock formations very impressive.

The morrow holds in prospect a visit to Bigge Island.  On the other hand, I’ve developed quite a severe sore throat. I hope that doesn’t presage anything unpleasant…