January 1996
It happened only recently; just the other day geologically speaking.
A couple of hundred kilometres south-west of what is now Cairns, the Undara volcano erupted. That was 190,000 years ago.
Lava spewed from the volcano covering some 1500 square kilometres. Liquid lava is like water. It does not spread out as a sheet, but rather forms rivers. This is what the Undara lava did. One such river flowed, red-hot at 1200 degrees, for 160 kilometres before the lava stopped spewing from the volcano.
As it flowed, however, it did something that rivers do not do. At the edges of the lava flow the lava was exposed to the air. It cooled and hardened. The hardened sides grew higher and higher while the lava still flowed red hot down the centre course. As the sides grew higher, they eventually closed over the top of flowing hot lava. Eventually the hot lava was flowing through a conduit pipe created by the hardened solid lava. It was flowing through a tube.
The volcano stopped spewing. The remnant of the molten lava dribbled through the tube and eventually the whole thing cooled, leaving one of the seven geological wonders of the Australia continent: the Undara Lava Tube.
The total lava flow was 160 kilometres … the longest known flow from a volcano. It was so long because of the large amount of lava (23 cubic kilometres), the speed of the flow and the fact it flowed into a pre-existing water course. Of the 160 kilometre flow, at least 20 kilometres formed into tube. Much of that has collapsed in the 190,000 years. But more than six kilometres of tube in two dozen sections remain. The longest surveyed is 1.3 kilometres long.
It is an awesome, eerie and sombre experience to descend into a segment of the Undara lava tube … perhaps it is slightly sullied by the geological knowledge of its creation.
The huge cavern, up to 20 metres high and 30 metres across dwarf the humans on its floor. What of the first man to go into it … most likely a stockman in the 1860s, for the Aborigines did not use the tube (it was too dark)? The stockman, perhaps unencumbered the knowledge of Darwin or even of the earlier work of Lyell and assuming the whole creation happened at once 4000 years ago, would have asked: what purpose here?
The caves are certainly home for bats, mostly (ital) Miniopterus schreibersii (end ital), but there are nine other species. They seemed to pour out from a crevice in the ceiling. Thousands of them. But their sonar enables them to dodge nosy tourists and they eat only insects.
The caves, like other hostile places on earth, are home to some extra ordinarily adapted creatures. Insects with small or no eyes and little or no bodily colour, but with very long antennas, feed on dead animals that found their way into the caves for a peaceful, more dignified, death away from the heat, flies and opportunist crows on the surface. Bodily colour, usually for camouflage or to protect against the ultraviolet light, is of no moment in the caves.
The insects and fungus feed also on roots that penetrate the ceiling and bat droppings. Lice even feed off live bats (see picture).
In one cave a remarkable frieze displayed the fortunes of nature. A snake had crawled to a spot on the ceiling, jamming itself in a crevice and dangling its head into mid-air waiting for an unsuspecting bat to fly too close, when it would lunge for a meal.
It stayed too long, missed its meal, got cold and did not have the energy to move. There it died. Its skin coated skeleton still dangles from the ceiling like a tree root, the flesh taken to feed voracious insects.
These tubes are the oldest in the world. The fragile lava in other tubes have collapsed in wetter and colder climates. Those in Hawaii and Iceland are visibly collapsing on the human time scale, let alone the geological one. However, some of the remaining lengths of tube in Hawaii are much longer than the longest lengths at Undara.
Undara means “”long way” in the local Aboriginal language. The name was given in the early 1960s by John Best from the Bureau of Mineral Resources. From a distant bluff he saw depressions containing patches of green and correctly identified them as “”collapsed lava tunnels”.
At various places along the 160 kilometres green patches appear in what is otherwise a brown terrain of sparse eucalyptus and grass.. These are the tops of rain-forest trees growing from the floor of the lava tube wherever the roof has collapsed to let in light. The rainforest has survived because the trunks are mostly below the normal surface line have been protected from fire, and the depressions, up to 20 metres below the normal surface, hold the water. (Incidentally the height of the lava tube in various places were measured by sending up a helium balloon with a string attached.)
In 1966, the words “”collapsed lava tunnels” on a BMR map caused bushwalker Norman Traves, who was working of a developmental road at the time, to investigate. He was stunned by their magnitude.
Undara was opened as a national park in 1992. Parts of Undara were leased back to Gerry Collins. The Collins family have worked the land for five generations. In 1990, Gerry Collins opened a tourist village using railway carriages dating back to 1888. There is also camping and other accommodation. (Phone 070 971411.) Before a couple of years ago very few people saw the caves. Even now they are not well-known.
Since 1972 they have attracted international academic interest after Australian geologist Anne Atkinson drew the attention of the US space agency NASA to aerial photographs of Undara that had an uncanny similarity to photographs of the basalt plains on the moon. The feature on the moon was a lava flow just like Undara.
Finally, a word of warning. Do not use the chunks of basalt around Undara as rocks for a camp fire. When the lava solidified it trapped a lot of gas. When the rocks are heated they explode. Flying bits have damaged cars and people.
Pics. 1. Guide Jamie Anderson explains the lava tube to a group of visitors to the Collins Road cave. 2. Looking out from Stephenson Cave. 3. A lice-infested bat in Collins Road Cave.