by Patrick Nunn
Such a situation is well illustrated by the highlands of New Guinea, where legends about ash falls – often celebrated post facto for the fertility they restore to overworked soils – proved almost impossible to link to particular eruptions or even particular volcanoes by themselves.2 New Guinea’s active volcanoes are mostly coastal, often forming offshore islands that trace arcuate lines of crustal-plate convergence. Rarely, it seems, is one or other of them not active, but it was a particularly active period when William Dampier arrived there in 1700, encountering five of these ‘burning’ islands. All night on 25 March, he reported that the first
… vomited Fire and Smoak very amazingly; and at every Belch we heard a dreadful noise like Thunder, and saw a Flame of Fire after it, the most terrifying [sight] that I ever saw.3
What of New Guinea’s southern neighbour, Australia, which as we have seen is today a somewhat geologically passive place? Have there been volcanic eruptions there within the 65,000 years or so that people have lived there?
Not surprisingly when you consider the vastness of Australia, the answer is yes. And yes, too, there are extant stories about some of these eruptions, which also comes as no surprise given the likelihood that Australia’s Indigenous peoples have preserved other stories for perhaps more than 10 millennia. Yet critically, these eruptions have been isolated in both time and space in Australia, making any associated oral traditions relatively easy to link to particular events and places. This condition makes Australia an excellent place to study the antiquity of these oral traditions, better for this purpose than New Guinea, Japan, Italy or Iceland, where the ubiquity of eruptions through time has rendered the relevant bodies of oral tradition far more nebulous and difficult to interpret.
The map in Figure 6.1 shows places in Australia where volcanic eruptions are known to have occurred within the past 65,000 years or so. They include at least five sites in northern Queensland (Lakes Barrine, Eacham and Euramoo; Kinrara and Nulla), five in southern Victoria (Napier, Eccles, Tower Hill, Warrnambool and Leura) and three just across the border in South Australia (Muirhead, Schank and Gambier). The activity of the volcanoes that these features represent must all have been witnessed by Aboriginal peoples and, as we shall see below, some of their observations have come down to us today.
It is something of a puzzle that young volcanic activity should have occurred on an ancient continent. Indeed, scientists are still struggling to explain some of this activity, although that in the south is possibly associated with the presence of a massive body of liquid rock – a mantle plume – that today lies beneath much of Tasmania and the adjacent ocean floor. This plume is a ‘hotspot’, a place where liquid rock from the Earth’s mantle protrudes into the overlying solid crust, coming so close to its surface (perhaps 80–150km/50–95 miles below it here) that some of this liquid rock has occasionally escaped upwards along cracks and come out at the Earth’s surface. It is not beyond the bounds of possibility that this might also occur in the future.
We know this mantle plume has been in existence for several tens of millions of years, for it first encountered the Australian mainland more than 33 million years ago to form the Mt Jukes Volcano (Cape Hillsborough), near what is now the central eastern Queensland coast (see Figure 6.1). As the Indo-Australian Plate continued its slow, inexorable progress north-northeastwards, as described in Chapter 2, so the mantle plume passed under the continent and formed a line of volcanoes, just like the classic hotspot chains of oceanic islands.4 The resulting Cosgrove Hotspot Track is some 2,200km (1,367 miles) in length, the longest hotspot track yet to be documented on a continent.
Figure 6.1 The eastern half of Australia showing all the volcanoes known to have erupted within the last 65,000 years, the probable time that Aboriginal people have occupied the continent. Four of these volcanoes are shown in northern Queensland, five in southern Victoria and three in the nearby part of South Australia. The origin of at least some of this comparatively young volcanic activity can be attributed to the presence of the mantle plume that created the Cosgrove Hotspot Track within the last 33 million years.
This mantle plume is implicated in the young volcanic activity that occurred in southern Australia, but exactly how is still something of a mystery. The volcanic activity defines the Newer Volcanics Province (NVP) and includes at least 704 points of eruption from at least 416 separate volcanic centres within an area of some 19,000km2 (7,336mi2). But as you can see from the map, the NVP does not lie on the Cosgrove Hotspot Track – it is not even really close. Yet, given that the earliest volcanic activity in the NVP began about five million years ago, the timing with the progress of the relative movement of the plume is about right; it would have been closest to the NVP at this time. So we can envisage a situation where a sizeable piece of the plume (a diapir) at this time branched or broke off to its west to form a body of liquid rock beneath this part of southern Australia where, for the next five million years or so, it has periodically leaked to create the NVP.5
Uncertainty feeds scepticism, especially when this fuels self-interest. The idea that scientists cannot explain why volcanic activity has occurred recently in Australia might indeed strain the credulity of some of its citizens about whether this activity really did occur. But we have two excellent ways of corroborating this: radiometric dating and, more tellingly for sceptics, eyewitness accounts.
Largely because its results contradict certain narrow partisan interpretations of the Christian Bible, the concept of radiometric dating has received a bit of bad press in some quarters,6 although it has been used routinely for decades by scientists to determine the ages of particular rocks. After these rocks first form, radioactive impurities within them start to change – or decay – over long time periods into different types of material. By knowing the rates at which such radioactive decay takes place, we can calculate the time that has elapsed since the formation of a particular rock by measuring the proportions in it of both the ‘parent’ radioactive substance and the ‘daughter’ (or decay product). Most volcanic rocks that have been dated, including those from Australia’s younger volcanoes, have been subject to age determination using the potassium-argon (K-Ar) method. In this, an isotope of potassium (40K) decays to one of argon (40Ar). For half the 40K present in the original rock to become 40Ar, it takes around 1.3 billion years, so you can see potentially how powerful this dating technique is. Almost every volcanic rock that became solid (cooled from a liquid state) within the past two billion years or so can be dated using this method.7
Another important radiometric dating technique is radiocarbon dating, based on the decay of the radioactive isotope of carbon (14C), and applicable to any substance with carbon in it. By measuring the ratio of 14C to the non-radioactive carbon isotope 12C, the age of a substance like a piece of shell, bone or hair can be measured. Its age is that from the time when the carbon-containing lifeform died, ceasing to renew its stock of 14C from the food it ate, until the present. With a half-life of 5,730 years and with quantities of the two isotopes able to be measured very precisely, radiocarbon dating has been used widely. You cannot use it on most volcanic rocks, but you can use it on some of the things that are buried when lavas flow (or hot rocks are blown) out of volcanoes. They include items like soils or shell middens, and even old fire pits containing charcoal and bones. Some of Australia’s young volcanoes cannot be dated directly because the erupted materials are too weathered; in such cases, radiocarbon dates from associated materials can be used to provide maximum (sometimes minimum) ages for a particular eruption.
There was once a man, a veritable giant named Craitbul, who with his wife, also of ‘immense size’, and two sons wandered through south Australia in search of a place where they might live in peace, free from fear of the evil spirit Tennateona.8 The family first settled atop Mt Muirhead, one of the younger volcanoes in the NVP, where they lived ‘for a considerable time in peace’. Accustomed to cooking food in the ground, they dug a hole there in which they placed their food, co
vered it with earth and went to sleep, anticipating that it would be cooked when they got up the next morning. But in the night they were awoken suddenly by the shrieking of a bird known as a bullin. Believing this portended the presence nearby of Tennateona, they fled, eventually settling on Mt Schank, where once again they camped and ‘began to enjoy themselves’. But one night, their cooking oven emptied, they were again awoken by the bullin’s cries and fled inland, away from the sea to which they believed Tennateona preferred to be close. They travelled to Mt Gambier ‘and lived here a long time’, as usual making their oven within it. But one day water rose up from below, putting out their oven’s fire. So they dug another, and the same thing happened, and so on and so on. Finally they gave up and were last heard of living in a ‘cave on the side of the peak’.9
If we equate the ovens with the craters within these mountains, then we could also read the cries of the bullin and the emptying of ovens as euphemisms for the alarm accompanying the eruptions of these volcanoes, as well as the facts of this. The four craters of Mt Gambier are maars, products of spectacularly explosive eruptions that occur when superheated liquid rock (magma) rising up a vertical fissure through the crust encounters cold groundwater. The resulting phreatomagmatic explosion shoots out lava fragments and ash in every direction. When these fall to the ground they often harden to form a circular ridge – marking the spatial limits of the eruption – which may later become filled with rainwater to form a maar lake. Most of the maars of the Mt Gambier region are today water filled, so we can interpret Craitbul’s ovens as being the active maar volcanoes that were subsequently flooded. It is hard to see what other interpretation might be placed on such a detailed story (see colour plate section).
How old might the story of Craitbul be? Radiocarbon dating of plant material buried within volcanic ash on the floors of the maar lakes of Mt Gambier suggests that the most recent period of volcanic activity here took place around 4,300 years ago, about the same time as the last eruption of Mt Schank.10 Several other Aboriginal stories report fire being thrown from these mountains, and at least one informant at Mt Leura identified some of the volcanic bombs, which are typical products of explosive eruptions, as just like ‘stones which their forefathers told them had been thrown out of the hill by the action of fire’.11
Mt Eccles is another young NVP volcano,12 and there are said to be Gunditjmara Aboriginal stories that recall its most recent eruption. This is likely to be that of the Tyrendarra lava flow, much of which is now as much as 33m (108ft) below the ocean surface. Yet when it formed it covered only dry land; it did not run into the sea. So while the lava flow itself has proved impossible to date directly, we can estimate a minimum age of 10,500 years ago for the eruption that formed it – the time when the sea floor now 33m deep was last dry land.13
Much of the realisation that Aboriginal Australians had witnessed volcanoes erupting came from understanding the meanings of place names. Among some of the early European settlers in parts of Australia, there was a tradition of recording Indigenous names for particular places, something that has occasionally been found to hold insights into their history.
There never were elephants living in Australia, so the name Mt Elephant for the young scoria cone volcano in south-west Victoria is clearly one given by European settlers, one assumes on account of the pachydermic appearance of the mountain from a certain angle. Yet far earlier in time, the Aboriginal people of the area called this mountain Gerinyelam, meaning ‘hill of fire’. Given that Mt Elephant formed 5,000–20,000 years ago, we can assume that its eruption was witnessed, a fact that was probably once preserved in stories that now appear to be lost, yet have their essence kept alive in the name Gerinyelam.14 Another example is that of the Gunditjmara people who call nearby Mt Eccles by the name Budj Bim (high head), and its associated spatter cones and tumuli tung att, or ‘teeth belonging to it’.15
What of the other group of youthful volcanoes in Australia, those in northern Queensland? Their origins are perhaps even more elusive than those of the NVP.16 Like this group of volcanoes, they exhibit no age progression in any direction, so that eruptions here cannot be readily explained by the movement of the Australian continent over a mantle plume, as can eruptions of the older volcanoes along the Cosgrove Track. Eruptions in northern Queensland have been continuing – on and off every 10,000 years or so – for the last nine million years, and the area is still considered ‘potentially active’.17
Aboriginal stories about eruptions in the Kinrara area belong to the Gugu Badhun people and describe events that may have occurred 7,000 years ago.18 One story recalls the time when the watercourses that flow through the area – and from which the local Aboriginal people rarely strayed far – caught fire. Another story is about a witch doctor who made a huge pit in the ground, filling the air with dust, in which people became disoriented and died. This eruption of Kinrara involved the emplacement of lava flows – some ran down the river valleys for tens of kilometres – which is a plausible explanation for rivers said to have caught fire. The dust cloud and the deaths of affected people are equally easy to explain, for this eruption – the youngest known at Kinrara – was focused on a crater (the witch doctor’s pit) and involved ash-rich eruptions likely to have created dense clouds suffused with poisonous gases that drifted over the surrounding area, killing many of its inhabitants.19
Further north, Lakes Barrine, Eacham and Euramoo on the Atherton Tableland are three maar crater volcanoes, one or more of which may have erupted during the time that people have been living in this area. By dating (using radiocarbon) the earliest layers of sedimentary fill in these craters, minimum ages for their formation – presumably during a volcanic eruption – have been obtained. In this way, we know that the most recent possible date for the last eruption at Lake Eacham was around 9,130 years ago; that at Lake Euramoo perhaps 15,000 years ago; and that at Lake Barrine some 17,300 years ago.
Several Aboriginal groups in the area have stories about the eruption of Lake Eacham (and Barrine and Euramoo in some versions), all of which are quite similar. The essence of these stories is that two newly initiated youths were confined to camp, as was common practice, while their elders went to collect food. Needing to defecate, one youth went a short distance into the bush, accompanied by the other – breaking the taboo. The boys saw a wallaby and one fetched a spear that his companion threw at the animal. It missed, instead hitting a flame tree that is sacred to the Rainbow Serpent, the most iconic supernatural being in the Dreamtime bestiary. Thereafter things began to go badly wrong, and when the elders returned from hunting, they knew it. For although it was the middle of the day, the sky turned blackish-red – the colour of a striking sunset – and shortly afterwards the earth began to ‘crack and heave, spilling out a liquid that engulfed the camp and all the people in it, and forming the three modern crater lakes’.20
Australian Aboriginal stories about volcanic eruptions have come to confirm what science has learnt only far more recently. We can rate the authenticity of these stories highly, for nowhere do we find them applied to features that are not youthful volcanoes. In northern Queensland, for instance, Aboriginal stories about eruptions do not refer to other, much older crater lakes like Lynch’s Crater, where the last eruption took place around 200,000 years ago, well before people first reached Australia. And in the NVP in South Australia, no Aboriginal eruption stories are applied to those volcanoes – like Mt Napier and Tower Hill – where the last eruptions occurred more than 30,000 years ago.
There are few other places in the world where indigenous stories, passed on orally, recall ancient volcanic eruptions that have been virtually unknown in modern (literate) times. Of course, such stories abound where there are currently active volcanoes that have been periodically active ever since people arrived in their vicinity. So while any associated oral traditions are of interest, they do not really hold any surprises.
Take the iconic Mt Fuji (Fujisan), a mere 100km (62 miles) from Tokyo on Honshu I
sland in Japan. Aside from its form – that of a classic volcano, which has been celebrated in Japanese art and spirituality for millennia, Fujisan has been periodically active. Although its last proper eruption was in ad 1707–1708, the mountain groans audibly at times and belches gases continuously from fumaroles along its periphery, all signs that this volcano is far from deceased. There are numerous oral traditions about Fujisan’s origin, one being about a giant who decided one day to fill up the Pacific Ocean with earth. Toiling all night, he was dismayed when dawn broke to find that he had made hardly any progress with his task, so he dumped the bag of earth he was carrying where Fujisan is today … and stomped off sulkily. While entertaining and possibly containing some geological detail – perhaps about how Fujisan was created quickly – the story does not supply any details that are not already glaringly obvious. Similar stories abound in Icelandic lore, for example, as well as elsewhere.21
In the islands of Hawaii there are numerous stories about volcanic eruptions, but here – with a degree of precision that is almost unique – it is chiefly genealogies passed on orally for several hundred years that can be used to date particular events, something that science has since corroborated. For example, Hawaiian traditions (mo’olelo) recall that during the reign of Keali’iokaloa (approximately ad 1525–1600), a young chief from the Puna district of the Big Island (often spelled Hawai’i to distinguish it from the name of the island group) failed to properly acknowledge Pele, the fractious volcano goddess, so she pursued him downhill at high speed and followed him into the ocean – a likely recollection of a lava eruption dated to the same period.