About Me

My photo

I've been a Canberran since moving here from Adelaide on the first day of 1980. I now live in suburban Duffy with my partner Louise Maher, ABC 666 radio and on-line journalist. Among my early memories is following Sleepy Lizards (Shinglebacks) around the paddocks north of Adelaide, guarded by the faithful bull terrier. I have always been passionate about the natural world, trying to understand how it works, how the nature of Australia came to be, and sharing those understandings. My especial passions are birds, orchids and mammals. For much of my life I have been a full-time naturalist, running bush tours, writing books etc, doing consultancies, presenting a regular radio slot on local ABC, chairing a government environment advisory committee and running adult education classes. Recently I have eased back somewhat, but am still writing, teaching, doing some radio work and running overseas tours - as part of my fascination with our Gondwanan origins I've been running tours to South America for the past decade. I was awarded the Australian Plants Society Award in 2001 and the Australian Natural History Medallion in 2006, both for services to education and conservation. In January 2018 I was awarded a Medal of the Order of Australia for 'service to conservation and the environment'.

Thursday, 28 September 2017

Undara Lava Tubes #1; volcanic landscapes

Australia, uniquely as a continent, has no active volcanoes (we don't count the sub-Antarctic island territories in this). We sit securely within the tectonic plate we ride, and the deep-seating grumblings and belches that produce volcanic eruptions and earthquakes tend to occur where two plates rub up against each other. Of course it was not always thus here, and there are plenty of extinct cones and remnants, quite a few of them well within human times. The most recent ones, in south-eastern South Australia and western Victoria, only fell silent a few thousand years ago. 

A series of volcanic landscapes dot the south-eastern hinterlands, including the Glass House Mountains, the Nandewar Range (Mount Kaputar NP), the Warrumbungles and Mount Canobolas, which erupted as Australia sailed north over a 'hot spot', which burst through as weaker or thinner sections of crust passed over it. Accordingly they get younger from north to south (from around 26 million years for the Glasshouse Mountains to 12 million for Canobolas).
Mount Canobolus, south-central New South Wales.
Undara, in north Queensland, is much younger however, dating from a mighty eruption some 190,000 years ago. 
Looking to Mount Undara, the centre of the eruption, across the woodland plains
from the rim of Kalkarni Crater. A walking track circumvents the Kalkarni rim and we shall come back to it.
It is said that more lava was produced here than by all the Hawaiian volcanoes; I have no idea if this
is true, or even what it means, but perhaps if you're familiar with Hawaii it might be helpful...
Other figures cited by presumably reputable sources are that the flow rate was sufficient to fill 1500 semi-trailers a minute (always assuming they didn't melt or explode of course), or Sydney Harbour in six days. It's unclear however how long this went on for, but the greatest extension from the source was a mighty 160km to the north-west. What is clear however is the legacy - the wonderful tubes. Where the lava flowed along river beds a rough cylinder of molten material formed; the exposed surface cooled and hardened while the insulated molten core flowed on and eventually out, leaving the hollow tubes. Undara is the longest volcanic tube system in Australia and the longest 'recent' (undefined) such system in the world. In time sections of the tube roof collapsed, forming open-ended caves, and it is some of those that we can visit, within the Undara Volcanic National Park. 
One of the Undara tubes which is open to the public.

Approximate location of the Undara tubes, some 300km inland from Cairns along
the Gulf Developmental Road. The nearest (small) town is Mount Surprise.
I have seen it implied that entry to the park can only be with an accredited guide, and that such a guide can only be provided by the company which runs the accommodation complex just outside the park. This is not true, and most of the park is readily accessible, though it is the case that the tubes themselves can only be entered with such a guide. These guides (look for the Savannah Guides signs) are also available elsewhere, eg Mount Surprise caravan park. In my experience these guides are very good, though of course there is variation, and it depends too on what your needs and expectations are.

Enough! Let's get into the tubes, and one thing that strikes is their size - they are enormous.
I don't normally include people in these photos, but it's really the only way to get the scale.
They are also very colourful and beautiful, though I'm of no help in interpreting the basis of these patterns I'm afraid. Hopefully you can just enjoy them with me.
The Mikoshi Tunnel.



The Dome.
Lava flow against the older granite, Mikoshi Tube.
In the quiet and dark of the tubes (in the longer ones you can be out of sight of the entrance and exit)
the appearance of tree roots is a reminder of the world outside.

Even up there though, the tunnels have a profound influence. Where they have collapsed, the gullies accumulate water in the Wet; even the ground above the tunnel roofs - which are largely impervious - retains water from the rains. Here, in the broader woodland landscape, vine forests grow, and their greener foliage seen from a vantage point traces the route of the tunnels across the landscape.
View from Kalkarni Crater rim; the green line of vine forest following the tunnel
can clearly be seen across the middle of the photo.
Vine forest - often called vine scrub or monsoon forest in Australia, and tropical dry forest elsewhere - is a form of rainforest which grows where the tropical summer rains are followed by a long dry season. They are lower, with a more open canopy, than other tropical rainforests, but retain the vines and epiphytes typical of 'true' rainforests where it rains all year round.

At Undara they are at their lushest in the drainage lines where the tunnels have collapsed, so are encountered as we enter and leave the tubes.
Vine forest growing outside the entrances to The Arch, above and below.


Vine forest seen from Mikoshi Tunnel.
The vine forests are not restricted to the depressions, though they are generally found in their vicinity.
Typical vine scrub, with the most prominent trees being Broad-leaved Bottle Tree Brachychiton australis,Family Malvaceae (formerly Sterculiaceae). They are deciduous, dropping their leaves in the dry to
conserve water; the vine forests as a whole are regarded as 'semi-deciduous'.
Near the tubes the lava spills across the ground, and vegetation has forced its way up through it.
Surface lava, above and below.
 

Inevitably too, lava appears on the surface around the numerous vents and craters, including Kalkarni Crater.
View into the extensive woodlands from Kalkarni Crater rim walk, with lava in the foreground.
Elsewhere the older granites make their presence felt in the woodland landscape.

Granite tors in tropical woodland, Undara.
These woodlands are magnificent, but they probably tend to be relegated to a 'background scenery' role here not least because they form such a dominant part of the northern Australian landscapes. I always revel in being in them.
Undara tropical woodland.
And with that I think we'll pause, and resume next time by meeting some of the plants and animals of Undara Volcanic National Park. I hope you can wait that long before rushing off to see it for yourself; sooner or later you really must do that though.

NEXT POSTING THURSDAY
(And remember that you can get a reminder when the next post appears by putting your email address in the Follow by Email box in the top right of this screen.)

3 comments:

Susan said...

As someone who regularly goes into 'caves' (in reality former underground limestone quarries) I'm not surprised you are not allowed in to the lava tubes without a guide. It's amazing how disorienting being underground is.

Ian Fraser said...

Oh yes, I'm not suggesting any disagreement with the policy. (I never feel comfortable underground actually, but it's always an amazing experience.)

Flabmeister said...

Following on from Susan's comment, when in France I occasionally found myself a bit disoriented after following a sign saying "Visitez nos caves." This correlated with redistribution of weight from my wallet to the owner of the caves.