by David Keys
Proto-Thailand—the Kingdom of Dvaravati—came into existence in c. A.D. 580. Proto-Cambodia (the Kingdom of Chenla) was born at virtually the same time, following the demise of the ancient Mekong Delta civilization of Oc Eo (Funan) sometime in the mid–sixth century. Proto-Malaya (the medieval Sultanate of Malacca) evolved out of a civilization in southern Sumatra that first emerged in the form of the Kingdom of Srivijaya in the middle of the seventh century, following the demise (probably as a result of the eruption) of the fierce prehistoric megalith-building warrior culture known to archaeologists as the Pasemah. And farther north, proto-Burma (the Kingdom of Sri-Ksetra) came to prominence around A.D. 600 following the demise of its apparently more ancient rival, the Kingdom of Beikthano.
Thus, in its own way, Southeast Asia too fits the wider pattern of planetwide sixth-century destruction and subsequent political reformation, which helped destroy the ancient world and ushered in the proto-modern one.
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R E C O N S T R U C T I N G
T H E E R U P T I O N
Reconstructing the immediate sequence of events associated with a volcanic eruption that occurred fifteen hundred years ago is a daunting task—but not an impossible one. Using historical, tree-ring, ice-core, and other data, it is possible to compare the event and its climatic consequences with more recent eruptions of known size and effect.
Using the quasi-historical account in the Javanese Book of Ancient Kings, it is possible, assuming the account to be at least part genuine, to gain an insight into specific aspects of the eruption itself. And using geological and volcanological knowledge of the area and records of more recent large eruptions, it is possible to reconstruct what probably happened.
Between 530 and 535, there would almost certainly have been a long series of earthquakes in what is now western Java, southern Sumatra, and the neighboring seas. These earthquakes and accompanying seismically triggered tidal waves may well have seriously disrupted life in the region. Typically, volcanic eruptions are preceded by increasingly frequent and violent tremors. Often the larger the eruption, the longer the seismic run-up to it will be.
In the case of the 530s catastrophe, the run-up to the eruption may even have included several earthquakes of level 6 on the Richter scale. Throughout the second half of 534, earthquakes would have struck the region at the rate of one or two per day. In the weeks immediately before the eruption, the rate would have accelerated to a peak of fifty quakes per hour in the final twenty-four hours, mainly in the range of 1 to 3 on the Richter scale.
Although it is a controversial proposal, it is geologically possible that Sumatra and Java were one island prior to the 535 supereruption—exactly as the Javanese Book of Ancient Kings describes.¹ The 535 eruption would therefore have burst forth from a volcanic mountain located on fairly low-lying ground where the shallow Sunda Straits between Java and Sumatra are today. For several years, a huge mass of molten magma would have been moving closer and closer to the surface—probably at the rate of up to thirty feet per month. This would have caused the land surface above to bulge upward into a low dome, increasing in height at up to three feet per year over perhaps a five-year period.
Then suddenly the pressure of the magma, two or three miles below the ground, would have proved too great; a crack would have opened up, and the first phase of the eruption would have started. A vast cloud of ash would have billowed forth, followed by a column of red-hot magma that would have shot out of the mountain like a fountain. A week or two later, as the magma came yet nearer to the surface, one of the earthquakes accompanying the eruption probably fractured the rock above the magma chamber, allowing the sea to rush into the wide tubes through which the magma was rising from the chamber to the surface. The second phase began with a vast explosive event that shot even larger quantities of molten magma into the air at up to 1,500 miles per hour, reaching heights of perhaps thirty miles. The sound from this explosion would have broken the eardrums of most humans and animals living within a fifteen-mile radius.
The shock wave from the explosion would have moved outward at 750–1,500 miles per hour, devastating everything in its path for up to twenty miles. Houses, bridges, temples, and every single tree would have been leveled like so many matchsticks. And within an estimated ten-mile radius there would also have been massive fire damage as the shock wave compressed the air, heating it to very high temperatures and causing combustible material to simply burst into flames.
Most of the molten magma fountain would have broken up into fragments ranging in size from less than a thousandth of an inch to a yard or more in diameter and would have partially solidified at an altitude of two or three miles. The larger fragments—along with car-sized chunks of the mountain itself—would have fallen back to earth within a radius of three to seven miles. The microfragments, however, would have been carried skyward by powerful convection currents.
As the second phase of the eruption continued, a vast mushroom cloud of ash and debris would have penetrated far into the stratosphere, reaching altitudes of up to thirty miles and carried aloft by extremely strong, high-temperature convection currents, moving at hurricane-force speeds.
In the center of the volcano, temperatures would have reached 1,650 degrees Fahrenheit, generating the heat that forced the ash cloud heavenward. As the mushroom cloud increasingly blotted out the light of the sun and day was turned into night, ash would have rained down on forests and fields alike up to a thousand miles away, and houses would have been shaken by the eruption at similar distances. The sea for dozens of miles around would have been covered with a six-foot-thick floating carpet of pumice, and ships at sea would have become terminally stranded in this volcanic quagmire.
Stupendous amounts of magma, vaporized seawater, and ultrafine hydrovolcanic ash (generated by magma-seawater interaction) would by now have been hurled into the sky, and a substantial percentage of it would have entered the upper part of the earth’s atmosphere, the stratosphere. As it spread sideways at high altitude, away from the immediate area of the eruption, the material cooled and the water-vapor component would have then condensed directly into vast clouds of tiny ice crystals. It is estimated that the entire eruption may have generated up to 25 cubic miles of ice crystals; spread out in a thin layer in the stratosphere, these would have caused sunlight diffraction and cooling over vast areas of the globe. Superfine hydrovolcanic ash and huge quantities of sulfur and carbon dioxide gas would have had similar effects. Unlike ordinary volcanic ash, which falls to earth within a few months, hydrovolcanic ash, high-altitude ice-crystal clouds, and sulfuric acid and carbon dioxide aerosols (minute drops) can stay in the stratosphere for years, forming a long-term barrier to normal sunlight and solar heat transmission.
Within hours after the start of the second phase of the eruption, part of the huge mushroom cloud above the volcano would have become too heavy with ash to stay aloft. This part would have collapsed back to the ground, spreading horizontally over land and sea in all directions away from the volcano in what is called a pyroclastic flow,² but thousands of times larger than similar flows that partly destroyed the island of Montserrat in the Caribbean in 1997–98.
This horizontally moving cloud would have swept across the ground (and the sea) like a boiling-hot tidal wave of steam, sulfur, air, carbon dioxide, carbon monoxide, ash, and rocks. This hot, poisonous wall of destruction, more than a thousand feet high, would have moved outward perhaps as much as forty miles from the volcano at up to 250 miles per hour, killing anything in its path.
Then, as the eruption progressed further, the third phase would have begun. Because the huge magma chamber beneath the surface was now partially empty, its roof would have been unable to support the weight of the rock above it. As a result, it would have fallen inward, causing a sudden catastrophic drop of between three hundred and a thousand feet in the level of the land above. As the land surface sank below the level of the adjacent sea, the sea itself would have surged in to cover the former land. Seawater would have aga
in come into direct contact with some of the remaining molten magma, and there would have been a series of immense explosions, producing even larger pyroclastic flows.
After the catastrophic pyroclastic flow, eruption, and caldera collapse, the fourth and final phase of the eruption would have begun. The explosions would have started to subside over a period of weeks or even months, during which quiet episodes might have persisted for several days or more, punctuated by eruptive bursts of dwindling power. The caldera probably left small island vents that continued to periodically belch steam and ash several miles into the sky for years to come as the residual magma deep below the caldera gradually was quenched.
Comparing this scientific account with the description in the Javanese Book of Ancient Kings, we can see that the whole event appears to have been recorded with some accuracy: “At last, the mountain burst into pieces with a tremendous roar and sank into the deepest of the earth. The water of the sea rose and inundated the land. The land became sea and the island [of Java/Sumatra] divided into two parts.”
In the past, virtually all geologists thought that the fall in land level could have been caused only by gradual tectonic forces. But a reanalysis of the available geological evidence carried out by volcanologists as part of the research for this book shows that that view is incorrect.³ The crucial land-level reduction that caused the formation of the Straits of Sunda could have occurred as a result of a volcanic caldera eruption. This geological evidence, when combined with the Chinese historical, Javanese quasi-historical, ice-core, and other evidence, makes the Sunda Straits caldera, proto-Krakatoa, the most likely site of the 535 supereruption.
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T H E E N D G A M E
The 535 eruption was, as near as can be determined, one of the largest volcanic events of the past fifty thousand years. Whether looked at in terms of short- and medium-term climatic effects, caldera size (assuming proto-Krakatoa was the culprit), or ice-core evidence, the eruption was of truly mammoth proportions. Climatologically, the tree-ring evidence shows that it was the worst worldwide event in the tree-ring record. Looking at the ice cores, we see that it may well have been the largest event to show up in both northern and southern ice caps for the past two thousand years.
And in terms of caldera size—again assuming that proto-Krakatoa was the culprit—the eruption resulted in one of the half dozen largest calderas known anywhere in the world. Up to ninety-six thousand cubic miles of gas, water vapor, magma, and rock were hurled into the atmosphere.
Most of the heavier material—rocks and larger ash fragments—and water vapor would have fallen straight back to earth as muddy rain. But much (perhaps 50 percent) of the water vapor, the other gases, and the hydrovolcanic ash penetrated the stratosphere and was light enough to stay aloft for years.
Some water vapor mixed with sulfur gas to form tiny drops of sulfuric acid. Most of the water vapor, however, condensed into tiny ice crystals, like frozen fog. And the hydrovolcanic ash dispersed widely in the stratosphere, forming a dust veil over the globe. All three materials would have formed single or multiple stratospheric layers cloaking most of the planet, conceivably with different or sometimes overlapping geographic distributions.
Depending on the number of layers involved, the thickness of each layer, their stratospheric distribution, and the material involved (ice, sulfuric acid, or hydrovolcanic ash), the amount of sunlight and solar heat penetrating these layers would have been reduced differentially in different parts of the world. In some areas where material was dispersing sunlight very effectively, the sun would have appeared to have lost much of its shine. In all areas, temperatures would have dropped. As the air cooled, the water vapor in it would have turned into water and would have fallen to the ground as rain. But the colder weather also meant there was less evaporation from the oceans and the land. So the sky would have run out of rain, and major droughts would have set in worldwide.
This is, of course, exactly what actually happened—in China, Japan, Mongolia, parts of Europe, Arabia, East Africa, Mexico, South America, and no doubt many other areas for which we have no direct information.
In the Northern Hemisphere, the summer monsoons would have weakened and become drier, while the winter monsoons would have become stronger but, once again, also drier. Of particular importance would have been the abnormally small amount of rain, probably over two or three years, produced by the northeast monsoon blowing from India to East Africa. It was this failure that caused bubonic plague to break out of its naturally immune wild-rodent pool and spread to the Mediterranean and Europe, changing the region’s history forever. The weakened summer southwest and southeast monsoons failed to bring rain to Mongolia and thus altered the political balance there in a way that was also to change world history.
In a “flip-over” phenomenon that is as yet poorly understood, long droughts frequently end spectacularly in large storms and massive floods. Because of the chaotic climate, these often feature giant hailstones the size of golf balls. If storms and floods had followed drought in East Africa in the sixth century, the plague’s breakout would have been even more spectacular than if only following a drought. The scale of the plague’s impact around this time strongly suggests that this drought/flood phenomenon was what actually occurred.
In the Southern Hemisphere, the cooling not only caused massive droughts but also interacted with the larger El Niño storms that periodically hit Peru. This interaction would have substantially intensified the El Niños, with devastating consequences.
Throughout the world, levels of pollution in the lower atmosphere (the troposphere) would have increased dramatically at various times of the year, as massive dust storms and forest fires broke out. Both are typical phenomena associated with drought conditions. The “yellow dust” that fell like snow in China and the dust layers detected in the Quelccaya glacier ice cores from Peru testify to the giant dust storms that must have engulfed many areas of the world.
The immediate effects of the 535 eruption and a possible second eruption from a different (and as yet unlocated) volcano in c. 540 lasted five to seven years in the Northern Hemisphere and even longer in the Southern Hemisphere. However, poorly understood climatic feedback systems were almost certainly responsible for years of further climatic instability (including subsequent droughts) in the Northern Hemisphere (up till c. 560) and in the Southern Hemisphere (up till the 580s). The eruption(s), directly and/or through feedback, altered the world climate for decades, and in some regions for up to half a century.
The explosion and climatic changes destabilized human geopolitics and culture, either directly or through the medium of ecological disruption and disease. And because the event, through its climatic consequences, impacted on the whole world, it had the effect of resynchronizing world history.
For the people who lived then, it was a catastrophe of unparalleled proportions. Procopius, referring to the darkened sun, later wrote that “from the time this thing happened, men were not free from war, nor pestilence nor anything leading to death.” However, for us today, the sixth-century catastrophe and the swirling tide of interacting events that flowed from it shed new light on the origins of our modern world, on the processes of history, and—perhaps most alarmingly—on the ultimate fragility of our planet’s human culture and geopolitical structure.
PART TEN
THE FUTURE
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B E Y O N D
T O M O R R O W
Brooding an estimated six miles beneath the scenic wonderland of America’s Yellowstone National Park is a vast liquid time bomb the size of Lake Michigan or the Irish Sea. Made of molten rock, this ultrahot subterranean reservoir of volcanic magma will almost certainly one day burst forth upon the world, changing our planet’s history just as proto-Krakatoa did fifteen centuries ago. For Yellowstone is host to the world’s largest dormant volcano—a huge caldera covering around fifteen hundred square miles.
It appears to erupt roughly once every 600,000 to 700,000
years—and the last eruption was 630,000 years ago. What’s more, the last decade or so of the twentieth century has seen a substantial increase in potential pre-eruption activity there.
Since 1988, upward pressure exerted by the magma reservoir and by magma-heated water vapor (around thirty-five thousand pounds per square inch) has forced hundreds of square miles of land to rise by approximately three feet. Moreover, the pattern of geyser activity at the park has begun to change.
Yellowstone is known to have erupted cataclysmically on three occasions in the past: 2 million years ago, when it spewed out nearly 600 cubic miles of magma; 1.3 million years ago, when it ejected “just” 70 cubic miles of the stuff; and 630,000 years ago, when it generated about 250 cubic miles of magma.
Of course, no one knows when Yellowstone will erupt again. But it’s a pretty safe bet that one day it will.
Another potential catastrophe in North America is a currently dormant supervolcano in Long Valley, California. Over the past twenty years this too appears to have become progressively less stable. Since 1980 some 18 million cubic feet of carbon dioxide gas has been ejected from volcanic-related vents, killing off dozens of square miles of local forest. What’s more, earthquake clusters are becoming much more intensive, with up to 1,600 tremors (each up to 3.5 on the Richter scale) per cluster. Local hot-spring behavior is also changing. The only known major eruption of Long Valley’s 212-square-mile caldera occurred seven hundred thousand years ago, and because records have been kept over only the past fifty years, no one knows whether the volcano’s current restlessness presages a massive eruption or merely the resumption of calm and tranquility.
