Catastrophe: An Investigation Into the Origins of the Modern World (41 page)

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 again 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.”

I
n 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.

T H E  E N D G A M E

T
he 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.

THE FUTURE

B E Y O N D
T O M O R R O W

B
rooding 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.

When Long Valley last erupted, it produced 125 cubic miles of magma and generated a pyroclastic flow of such vast proportions that when the wave settled it added 350 feet to the surface height over several hundred square miles.

H
alf a world away in Europe, another vast caldera is beginning to flex its volcanic muscles. Just three miles beneath the western suburbs of Naples is a huge magma reservoir containing between 70 and 250 cubic miles of molten rock. Since 1969 pressure from this magma has caused land to rise and fall twice—by about six feet. In the early 1980s it generated up to three hundred small earthquakes per week (each up to 4.2 on the Richter scale). There is no doubt that this caldera, known as the Campanian/Campi Flegrei complex, is becoming increasingly restless.

So far, it is known to have erupted cataclysmically twice—once thirty-seven thousand years ago, when it ejected 20 cubic miles of magma, and once twelve thousand years ago, in an explosion about a sixth of the size of the earlier one. In the first eruption the pyroclastic flow—the wave of superheated dust and gas surging along the ground—was so deep that it engulfed three-thousand-foot-high ridges thirty-five miles away.

The Campanian/Campi Flegrei caldera complex¹ is about 150 times as large as the crater area of the more famous nearby volcano of Vesuvius, which in
A
.
D
. 79 produced less than half a cubic mile of magma when it erupted. Again, no one knows when the Italian caldera will explode again on a truly massive scale but, like Yellowstone and Long Valley, it is virtually certain to do so one day—perhaps, in this European example, sooner rather than later.²