DiNo's Travels Around Australia - 2014/2015/16/17: 10 June 2017

We awoke to a cold morning at Undara but also to visions of pinkness invading our caravan. Something was going on. A look outside revealed the source, a most beautiful sunrise, but it did not help the thirsty birds.

100617 Difficult to get a drink at Undara if you are a currawong

100617 Sunrise at Undara

That got us moving and, albeit with stubborn knees resisting, we made it to the assembly point for the tour of the Undara Caves. The tour was for the more mature tourists, to caves with more comfortable acceses. We were taken by bus to the sites we were to visit.

Firstly, here is some background. The lava tubes are the result of volcanic activity over many years, although these caves are young in a geologic time frame. Undara erupted around 90,000 years ago. There have been around 72 eruptions over the last eight million years. Each has provided its own unique lava layer.

The eruptions came from a number of shield volcanos of which Undara was one. Undara is thought to have been about 20m high by 300m across. It spewed lava out at a rate of 1000 cubic metres/sec for 8-12 months. An aside: The lava covered the ancient granite landscape. The porous lava covered the impervious granite, which has left today, a water table about 15-30m below the surface, and an excellent source of water for graziers/stock.

Continuing - The lava covered up to 1500 square kilometres. It was presented with three key ingredients to form lava tubes, volcanic activity, a temperature of around 1200-1600 degrees centigrade and a gradient. As it slowly moved over the countryside it cooled progressively in parts, while allowing still molten portions to move outwards along what were now tubes. Over time portions of the tube roof collapsed. These collapsed sections have become access points to the tubes. There are around 69 caves in the region with public access to only 9 currently. The others are dangerous to enter for a number of reasons.

The lava tubes in this area are amongst the longest in the world. Undara's tubes are about 38km long. The aboriginal meaning of Undara is "long way".

The tubes and collapsed sections can be identified at the surface by dense evergreen vine thickets and some large trees. These are quite a contrast to the savannah woodlands, comprising sclerophyll forests of typically eucalypts, wattles and banksias with hard, short and often spiky leaves, which surround the tubes. The green thickets, and hence the route of the tubes, are evident from the aerial maps.

100617 Dry sclerophyll forest surrounding the caves

Today we visited two sites, The Archway and Stephenson Cave.

100617 Satellite picture of the area containing the lava tubes.
The dark lines just above the word Stephenson Cave are the
green foliage associated with the tube cave ins

100617 Aerial view of the caves. Note the greenery indicating
the position of the caves. The arrows show the
direction of the lava flows

100617 Pictorial representation of the cave formation on the LHS

100617 The walkway to The Archway

100617 More of the walkway

100617 The lava tube roof has collapsed

100617 The Archway up close

100617 Entering the Archway

100617 The roof of The Archway

100617 Looking out from under The Archway

100617 Heading into Stephenson Cave

100617 It goes further in

100617 Looking back at the entrance to Stephenson Cave
from further in the cave

100617 Another view of the entrance to Stephenson Cave
from further in the cave

100617 Another view of the cave entrance from within

100617 Brilliant ceiling effects - variations in lava composition,
extent of cooling etc

100617 More ceiling effects

100617 A microbat in Stephenson Cave - about the size of a mouse

100617 Roots from a fig tree near the entrance

100617 A broad leafed wattle tree (?) in a green thicket

Following are a couple of videos taken at the Undara caves.

100617 The Archway

100617 Looking out of Stephenson's Cave

We were quite impressed with our Undara experience and were tired but happy as we headed off to Atherton on the Atherton Tablelands. As we reached Ravenshoe, there was a pronounced change in the countryside. Gone were the savannah woodlands to be replaced by moist tropical rain forest flora, running streams, Baron and Millstream amongst them. We drove in and out of rainforest, crops and fields of green grass as we progressed from Ravenshoe to Atherton, where we will stop for a while - administrative needs. Sadly the weather has turned overcast and there is no sun. This means cool days when you are on the Tableland.