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The Edge of Memory

Page 18

by Patrick Nunn


  There are three other examples of stories about volcanic eruptions that are worth mentioning since they contain significant information about particular events that science has not yet been able to fully verify.

  The first example comes from the north-west United States, where lies Mt Rainier, perhaps the most potentially hazardous volcano in the Cascades. Rising almost 4,400m (14,436ft) above the ocean, Rainier can be clearly seen from most of Seattle and other densely populated coastal areas of Washington State. Rainier has been periodically active for most of the 15,000 years or so that people have lived in North America, and they have witnessed – and presumably struggled to rationalise – the multifarious expressions of its activity. In a Nisqually Native American oral tradition, Rainier is a monster that moved through the landscape swallowing every creature it encountered, until one day it met a fox that had wilily fastened itself to a neighbouring mountain. Exerting itself to try and devour the fox, Rainier eventually burst a blood vessel, causing rivers of blood to flow down its flanks. It is suggested that this myth recalls the time some 5,600 years ago when a phreatomagmatic eruption at the top of Mt Rainier produced the phenomenal Osceola Mudflow, which travelled more than 120km (75 miles) (to the outskirts of modern Seattle), eventually covering an area of more than 200km2 (77mi2). Studies of the nature of the flow structures within the mudflow sediments show that it moved as much as 19m (62ft) a second across the Puget Sound lowland – by any yardstick, a dramatic and memorable event worthy of becoming the subject of an important and enduring myth.

  The second example comes from Indonesia, some of the islands of which are spectacularly volcanically active, lying above the place where the Indo-Australian Plate is being thrust beneath its Asian counterpart. The 1883 eruption that destroyed the island of Krakatau (Krakatoa) and was heard across 8 per cent of the Earth’s surface occurred here for this reason.22 Plate underthrusting and associated melting at depth also explain the brooding presence of the volcano of Tangkuban Parahu in western Java, 17km (11 miles) north of the city of Bandung, home to some three million souls, most of whom have witnessed (or will witness in their lifetimes) activity at this volcano (see colour plate section). A Sundanese oral tradition, first referred to in the Bujangga Manik (56 lines of narrative verse written about 500 years ago on 29 palm leaves), explains that a young man named Sangkuriang was once whacked over the head with a centong (rice scoop) by his mother, Dayang Sumbi, sustaining a wound that left a permanent scar. Sangkuriang and his mother parted company after this, but when he later went in search of a wife he fell in love with her, not knowing that she was his mother, and determined to marry her. But Dayang Sumbi felt the scar on his head and knew he was her son, so refused to marry him. Sangkuriang was undeterred, so Dayang Sumbi challenged him to do what she thought was impossible – to create in one night a huge lake and a giant boat (parahu) for them to sail there. Damming the Citarum River and felling a giant tree, Sangkuriang almost did the impossible. Seeing this was about to happen, Dayang Sumbi caused the dawn to rise early that day and the cocks to crow. Believing then that he had failed, Sangkuriang smashed the boat, turning it upside down (tangkuban), and eventually both he and his mother drowned when the dam broke and the lake emptied. It is the existence of a former lake atop Tangkuban Parahu that gives some authenticity to this story as deriving from an eyewitness account. While poorly dated, it is clear that the Citarum Valley was once dammed by landslides, causing a lake to form and eventually to empty, perhaps 16,000 years ago.23

  A final example comes from Eurasia, from the breathtakingly beautiful Caucasus Mountains that mark the border between Georgia and Russia, and which formed as a result of the compression between the Arabian and Eurasian crustal plates. Numerous volcanoes, the highest of which are snow covered, tower over the landscape. Many have been active within the last few thousand years, a clear sign that a mantle plume has formed beneath the mountain range, exploiting lines of crustal weakness created during the prolonged compression. Even a passing acquaintance with Caucasian (sensu stricto) cultures is likely to throw up the name of Amirani, a hero of the region best remembered for having been chained to one of its mountains and attacked – like the Greek Prometheus and the situation at Mt St Helens (see colour plate section) – by an eagle drawing his blood. Another common story about Amirani relates how he cornered hordes of demons within the walls of a mountaintop fortress, then proceeded to massacre them; so much blood was spilt that the fortress walls finally gave way and rivers of blood poured down the sides of the mountain.24 Like the Promethean stories about Amirani, this one seems likely to recall a volcanic eruption, but from where and when? Within the Caucasus, the greatest concentration of Amirani traditions appears to be associated with Mt Kazbek volcano, which has not erupted for about 6,000 years. A better candidate for the Amirani stories may be Mt Elbrus, the highest in the range, which last erupted about ad 320 and may be due for another period of activity soon.25

  A summary of the likely longevity of the examples of volcano stories, preserved for most their time in oral form, is shown in Figure 6.2 overleaf.

  There is no question that ancient stories of volcanic eruptions and kindred phenomena exist in many of the world’s cultures and may extend back many millennia, perhaps 10 millennia in the cases of Eccles and Eacham, and possibly even more for Tangkuban Parahu. Science is indebted to indigenous stories of this kind, not simply because they confirm the existence – and sometimes give insights into the nature – of particular volcanic events, but also because in some cases they identify events that may not hitherto have been detected by scientific investigations.

  The upper parts of our oceans are alive, yet much of what lives there is so small that we cannot see it with the naked eye – so often we naively assume the ocean water we swim in to be clean. It is not. Microscopic carbon-based organisms, often lumped under the name plankton, abound. When they die, their hard parts usually sink to the ocean floor, sometimes kilometres deep, where they may become buried by layers of sediment. They are out of sight but certainly not out of mind for heterotrophic bacteria,26 which eventually find and consume them, releasing methane gas in the process. Pressure forces this gas upwards from the warm places within the sediment pile to its surface – the ocean floor – where it is much colder. Sometimes ocean water here becomes frozen around handfuls of gas, forming layers of methane hydrates that can themselves become buried at shallow levels within ocean-floor sediment. Now imagine this happening when the sea level was lower, as it was by 120m (400ft) or so during the last ice age; then what happens subsequently as the sea level rises rapidly thereafter. Suddenly the weight of seawater above the layers of methane hydrates – layers of ice-encaged lumps of methane – increases, perhaps to a point where the ice cages are smashed and the methane escapes. The whole pile of sediments in which the gas hydrates had existed becomes buoyant, and is destabilised and liable to collapse.

  Figure 6.2 Probable ages of volcanic eruptions recorded in oral traditions from Australia and elsewhere, details of which are in the text.

  Known as the clathrate-gun hypothesis, this explanation for massive collapses of continental fringes may account for why so many such collapses occurred during the time of postglacial sea-level rise.27 In such cases it is often not the slide itself that causes most problems for people, but the massive waves it generates that can wash across nearby coasts. A little over 8,000 years ago, a sizeable chunk – more than 3,000km3 (720mi3) – of the Norwegian continental shelf abruptly collapsed, creating what has become known as the Storegga Slide. It generated waves 12m (40ft) high that swept across nearby coasts and even travelled further afield. The main wave is estimated to have been 20m (65ft) high when it reached the coasts of the Shetland Islands, and a couple of metres lower when it smashed into the Scottish mainland, inundating coastal settlements with little warning and scattering the stone tools used by their inhabitants across a wide area.28

  No oral traditions of this event have come down to us today, perhaps bec
ause it was so long ago and the subsequent admixing of people in many of the affected areas militated against the preservation of ancient stories. You can bet there were oral traditions about the Storegga Slide in Norwegian and Caledonian cultures, reflected echoes of which may be found in their extant myths about the destruction of worlds,29 although no specific connections have been identified. The same is not true of other places where land has abruptly disappeared.

  In island worlds, it is possible for entire islands to disappear comparatively quickly,30 something that would clearly have caused consternation among the people of neighbouring islands, who often encoded their observations of such events in myths. To understand how an island might disappear, consider that most islands – especially those of volcanic origin in the middle of oceans – are both steep-sided and may have only a few per cent of their total mass exposed above the ocean surface. Just as happens on any steep-sided landform, landslides occur regularly on the sides of these islands, particularly those that are occasionally rocked by earthquakes. Such landslides – or flank collapses as geologists more commonly refer to them – may take a chunk out of the side of an island or even remove its top, its entire above-sea portion. In the greater scheme of volcano and island evolution, this is not really significant, but to the air-breathing occupants of the island and its neighbours it is massive.

  One comparatively well-documented example of such a ‘vanished island’ comes from the Solomon Islands archipelago in the south-west Pacific Ocean, where once an island named Teonimenu existed. Even though it disappeared hundreds of years ago, people living on nearby Ulawa Island know where Teonimenu was. Today it is a favoured fishing ground of theirs, with the top of the ancient island now being a submarine bank (named Lark Shoal) some 10m (33ft) below the ocean surface. The Ulawans say that on a placid sea, watchers may look down from boats above and see the ancient structures that people once made on Teonimenu, and sometimes even hear the beating of their drums and the sounds of their voices …

  Like Ulawa today, Teonimenu was once an emergent part of an undersea ridge, steepest on its eastern side where the sea floor descends to the Cape Johnston Trench, where a crustal plate further east is (or was) being thrust beneath that to the west. The area is often shaken by earthquakes, perhaps caused by nearby underthrusting of one plate beneath the other or – more likely given the origins of most of the area’s recent seismicity – the north–south compression of the Earth’s crust here. For the Solomon Islands rise from an isolated chunk of the Earth’s crust that is being compressed obliquely between the northward movement of the Indo-Australian Plate and the north-westward movement of the Pacific Plate. The result is that the Solomon Islands are uncommonly subject to earthquakes, some of considerable magnitude, which often generate tsunamis and may cause land to rise or fall abruptly. It is likely that, one day a few hundred years ago, a sea-floor earthquake close to Teonimenu caused tsunamis but also shook the island so much that it slipped a few tens of metres downslope in a massive flank collapse, removing itself in an instant from the human geography of the central eastern Solomon Islands.

  The story has reached us today through the mouths of local people, who will tell you about mad jealous Roraimenu from nearby Ali’ite Island, who married a capricious black-eyed beauty from Teonimenu named Sauwete’au. Tiring of Roraimenu, Sauwete’au one day eloped and returned to Teonimenu. Without compromise in mind, her husband went to consult a spell-seller on a nearby island, then sailed for Teonimenu prepared to plant the wave curse he had purchased there in order to destroy his errant wife’s island. As he sailed on his way there, grim-faced, people on nearby islands, alerted to his purpose, called out to him in fear, ‘Which island are you going to destroy?’ (Hanua i hei oto a nai warea?), but Roraimenu did not respond. Placing the curse on Teonimenu, he then retreated to a high point on Ali’ite to watch the destruction of Sauwete’au’s island. The water around Teonimenu churned and it was hit by a succession of giant waves as it sank beneath the ocean surface, never again to be seen. Oral histories from neighbouring islands recall how some inhabitants of Teonimenu saved themselves and where their descendants live today. Clearly the disappearance of Teonimenu resonated throughout this part of the Solomon Islands.31

  For a second example of an island collapse, we turn to the Marquesas Islands of French Polynesia in the Central Pacific. The Marquesas are volcanic and are something of an enigma to oceanic geologists, for the total volume of material making up the islands today is just a fraction of that which has been eroded off them and encircles them in a vast debris apron. The inescapable conclusion is that these islands have many times built themselves up to a state rather like they are in today, before being almost wholly eroded, then rebuilding themselves, and so on and so on.32

  There is today a rather insignificant uninhabited rock named Fatu Huku in the Marquesas, but when Captain James Cook visited these islands in 1774 it was much larger and probably populated. Yet Porter’s map of 1820 showed Fatu Huku to be much as it is today, perhaps a twentieth of its original size, and thus likely to have been affected by a collapse that led to the disappearance of most of the island within the interregnum.33 Believing that Fatu Huku was once supported by a pillar of rock rising from the Earth’s interior (it was not), Marquesan legends attribute its collapse to the shark guardian of the island which one day – to punish its dissolute inhabitants – used its tail to lash the pillar, causing it to break and the island to topple over into the sea.

  Something similar is found in Native American traditions, especially along the coasts of Cascadia where massive earthquakes, some of which lowered coastal lands abruptly, periodically occur. Consider the Yurok story in which

  … Earthquake and Thunder were wandering across the land, discussing the form it should take. When they decided that the ocean should come farther inland, Earthquake told his companion, ‘It will be easy for me to do that, to sink this prairie’. So as they traveled [sic] together, ‘They kept sinking the ground. The earth would quake and quake again and quake again. And the water was flowing all over’.34

  Yet in this region, as elsewhere, observers tended to place more emphasis on the earthquake-generated waves – the tsunamis – than the land movements that actually cause the disappearance of coastal land.35

  This brings us to Atlantis, the fabulous island-continent described by Plato around 360 BC, which he wrote had abruptly and cataclysmically vanished beneath the waves. Atlantis never existed and no amount of wishful thinking – and there is certainly an abundance of that – can make it otherwise, but Plato wanted to make his story sound as realistic as possible, so he stitched together details from actual events to create his enduring fiction. Since he required Atlantis to disappear, it follows that many of these details referred to land sinking, often near instantaneously, examples of which were well known to scholars in Ancient Greece.

  Many earthquakes occur on the Greek peninsula and in the Aegean Sea. The Gulf of Corinth, west of Athens, has been a major focus of earthquakes in recent times, as it undoubtedly was during the time of Plato. We have some information about ancient earthquakes there. For example, in 464 BC, a mere 37 years before Plato was born, an earthquake flattened the city of Sparta and was probably much talked about during Plato’s formative years.36 For earlier evidence of the power of earthquakes to destroy cities, Plato need have looked no further than the island of Crete, where the Minoan settlements (their ruins still visible) of Agia Triada and Phaistos had been destroyed by massive earthquakes about 1700 BC.

  Then in 426 BC, when Plato was just a baby, the Maliakos Gulf Tsunami affected parts of Greece, and it is likely that the reports of this came to influence Plato decades later when he wrote his story of Atlantis. At the time of this memorable tsunami, the Peloponnesian War between Sparta and Athens was in its sixth year and would last another 14. In this particular year, according to Thucydides, the principal chronicler of the war, the Spartans (heading the Peloponnesian League) were ready to invade Athenian terr
itory,

  ... but numerous earthquakes occurring, turned back again without the invasion taking place. About the same time that these earthquakes were so common, the sea at Orobiae, in Euboea, retiring from the then line of coast, returned in a huge wave and invaded a great part of the town, and retreated leaving some of it still under water; so that what was once land is now sea; such of the inhabitants perishing as could not run up to the higher ground in time. A similar inundation also occurred at Atalanta, the island off the Opuntian Locrian coast, carrying away part of the Athenian fort and wrecking one of two ships which were drawn up on the beach.37

  While it is likely that some of this detail was written down in Plato’s time, Classical Greek culture was still largely an oral one. Plato would routinely have heard the tales of travellers from distant lands, and his imagination would probably have been stirred by some of the outrageously fanciful explanations for natural phenomena they related, his mind likely wondering at the gullibility of people and plotting plausible scenarios for Atlantis, his ideal society gone bad.38

  On 30 June 1908, a sizeable rock – probably an asteroid some 60–70m (200–230ft) in diameter – entered the Earth’s atmosphere. Between 6 and 10km (4–6 miles) above the Earth’s surface in Tunguska, Siberia, it exploded. The blast was powerful enough to flatten more than 2,000km2 (772mi2) of the larch forest that swathes the natural taiga landscape in this sparsely populated part of modern Russia.39 When scientists finally surveyed the area almost 20 years later, they had to be ‘indirect and circumspect’ when questioning Evenki eyewitnesses to this event, since many believed it had been a visit by their fire god, discussion of which – as for the Klamath entering the vicinity of Crater Lake in Oregon (see Chapter 1) – was awkward because of its religious and cultural connotations.

 

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