Volcanoes

Crucibles of Change

Richard V. Fisher, Grant Heiken, Jeffrey Hulen

• Publisher: Princeton University Press
• Year: 2021
• Print ISBN:
  9780691002491
  9780691012131
• eBook ISBN:
  9780691238210
• Topic: Sciences physiques
• Subtopic: Géologie et sciences de la Terre

Whenever a volcano threatens to erupt, scientists and adventurers from around the world flock to the site in response to the irresistible allure of one of nature's most dangerous and unpredictable phenomena. In a unique book probing the science and mystery of these fiery features, the authors chronicle not only their geologic behavior but also their profound effect on human life. From Mount Vesuvius to Mount St. Helens, the book covers the surprisingly large variety of volcanoes, the subtle to conspicuous signs preceding their eruptions, and their far-reaching atmospheric consequences. Here scientific facts take on a very human dimension, as the authors draw upon actual encounters with volcanoes, often through firsthand accounts of those who have witnessed eruptions and miraculously survived the aftermath.


The book begins with a description of the lethal May 1980 eruption of Mount St. Helens--complete with an explanation of how safety officials and scientists tried to predict events, and how unsuspecting campers and loggers miles away struggled against terrifying blasts of ash, stone, and heat. The story moves quickly to the ways volcanoes have enhanced our lives, creating mineral-rich land, clean thermal energy, and haunting landscapes that in turn benefit agriculture, recreation, mining, and commerce. Religion and psychology embroider the account, as the authors explore the impact of volcanoes on the human psyche through tales of the capricious volcano gods and attempts to appease them, ranging from simple homage to horrific ritual sacrifice.



Volcanoes concludes by assisting readers in experiencing these geological phenomena for themselves. An unprecedented "tourist guide to volcanoes" outlines over forty sites throughout the world. Not only will travelers find information on where to go and how to get there, they will also learn what precautions to take at each volcano. Tourists, amateur naturalists, and armchair travelers alike will find their scientific curiosity whetted by this informative and entertaining book.

PART I

Volcanoes and Eruptions

CHAPTER 1

Politicians and Volcanoes

Frontispiece. A herd of elk crosses forest devastated by the May 18, 1980, eruption of Mount St. Helens, Washington. No matter how desolate an area may be after a volcanic eruption, life is quickly reestablished and can flourish after a few decades. (Photo: Richard V. Fisher)

Fig. 1-1. Washing clothes along the Rivière Roxelane—a typical day in the city of St. Pierre, Martinique, before the eruption of Mount Pelée in 1902. The sturdy stone houses were characteristic of this port city, which was then known as the Paris of the Caribbean. (Photo: Heilprin, 1908; Geographical Society of Philadelphia)

It was a coincidence of geography. On May 8, 1902, the beautiful city of St. Pierre, Martinique, known as the Paris of the Caribbean, happened to be in the killing path of a searingly hot volcanic hurricane that swept down the flank of Mount Pelée and killed 29,000 people. And it was a circumstance of timing that the city was in the process of election campaigning. It was an atmosphere doubly charged with election politics and a volcano that had been acting up for a couple of months. People were ambivalent about leaving: on the one hand, they wanted to support their candidate, but on the other, the explosions, rumblings, and sulfurous smell of the volcano frightened many, some of whom chose to leave the area. And yet, there were some curious people who came to St. Pierre from other towns and villages to watch the eruption. In 1902 volcanologists had a very rudimentary knowledge about volcanic processes and did not know that volcanic hurricanes (pyroclastic flows: pyro = “fire”; clastic = “broken”) existed. Hence this eruption made Mount Pelée the greatest killer volcano of the twentieth century. If the precatastrophic volcanic activity then shown by Mount Pelée were to occur today, modern volcanologists, having gained ninety years of cumulative experience since the 1902 eruption, would very likely urge immediate evacuation of the city regardless of other circumstances.

Gaston Landes, a professor at the high school in St. Pierre in 1902, said that ash and the sulfur smell from Mount Pelée would not cause great damage, and if the volcano erupted lava flows, they could not reach the city because too many ridges and valleys stood in the way. He was right about the lava flows, but he did not know about hot pyroclastic flows. He gave assurances that little damage would occur even with a big eruption. But on May 8 at 8:03 A.M. the most explosive eruption began, and within five minutes the pyroclastic flow swept through St. Pierre, blowing away, burying, and burning buildings and people. Those not killed outright by physical force died by inhaling ash, which clogged their nasal passages and trachea, and searing gases, which scorched their lungs (figs. 1-1 and 1-2).

The eruption of Mount Pelée drew the world’s attention to the existence of pyroclastic flows and started a line of research that is still continuing (see chap. 5). Since 1902, volcanologists have gathered considerable information about the behavior of volcanoes. They now have instruments to detect the small swellings of a volcano that indicate molten rock (magma) is rising into the edifice of the volcano. Seismologists, using seismographs, can find the origin of an earthquake (the focus) below a volcano and pinpoint the depth at which magma is stirring. Gases that originate from magma and reach the surface can be analyzed. One of these gases is sulfur dioxide, which indicates that live magma is moving upward through the volcano and may erupt. The presence of older rock fragments within the exploded debris suggests that the explosions are caused by groundwater that flashes to steam from the heat of the underlying magma and blasts apart preexisting solid rock. The presence of newly solidified pieces of magma suggests that magma could be approaching the surface.

Fig. 1-2. The eruption of Mount Pelée on May 8, 1902, devastated much of St. Pierre, leaving piles of rubble and half-standing walls. Sturdy stone walls were knocked down by powerful fast-moving clouds of hot dusty gas, known as pyroclastic surges or “volcanic hurricanes.” Note that the volcanic hurricane left no discernible volcanic deposit on the rubble that covered Rue Victor Hugo. Nearly all of St. Pierre’s residents died from the blast, burns, or asphyxiation. (Photo: Heilprin on May 14, 1902. Published in 1908 by the Geographical Society of Philadelphia)

Knowledge of volcanic behavior gained during the twentieth century was used by volcanologists at Mount St. Helens in 1980 to warn of impending danger, but as with Mount Pelée, volcanologists still did not have enough information to predict with certainty how Mount St. Helens was going to behave.

A Modern Tragedy: Mount St. Helens

On March 25, 1980, a group of geology students and three professors (including one of the authors—RVF) from a class in volcanology at the University of California at Santa Barbara visited the Hawaii Volcanological Observatory. We went to the wrong place to witness the beginning of an eruption, for on March 27, Mount St. Helens would erupt. But we did learn from an excited seismologist at the observatory that an earthquake of magnitude 4.1 had occurred beneath Mount St. Helens in southern Washington on March 20, ending the volcano’s 123-year rest. Other earthquakes at Mount St. Helens before March 27 had caused cracks to appear in its summit glaciers. Had we gone to the chain of volcanoes that forms the backbone of the Cascade Mountains instead of to Hawaii, we would have witnessed the modest beginnings of one of the most highly publicized and intensely studied eruptions of the twentieth century. Then, on May 18, 1980, nearly two months after the first stirrings of Mount St. Helens, the volcano turned violent.

An Eruption Carnival Turned Tragic

Mount St. Helens was center stage and people came for the show. During the interval prior to its climactic eruption—from March 20 to May 17, 1980—the volcano entertained the public. Mount St. Helens’ antics and its potential for danger drew people from everywhere. Entrepreneurs sold T-shirts, cups, posters, and bric-a-brac labeled with humorous slogans and cartoons (fig. 1-3). The main evacuation artery north of Mount St. Helens, Washington State Highway 504, was jammed with sightseers, there to witness the first eruption in the lower forty-eight states since Mount Lassen erupted in 1914. Some people said they came to see the “big one.” Cups of coffee and snacks were sold by the thousands. Roadblocks challenged some of the spectators, who then broke them down or snuck around them. State officials set up a “red zone” around Mount St. Helens to keep people from possible harm should there be an eruption (fig. 1-4); however there were not enough personnel to monitor the roadblocks twenty-four hours a day. The activity of the volcano excited people, and they wanted to see it. But at 8:32 A.M., May 18, 1980, the carnival turned tragic with a violent eruption. Many people, some on official business, died within the red zone. Volcano watchers, as well as campers thought to be in safe zones and out of sight of the volcano, were also caught in the doomed area.

On the quiet, sunny morning of May 18, Charles McNemey, John Smart, and several other people had found their way to an overlook to watch Mount St. Helens, just in case it erupted. They had a good view of the volcano from a cleared area along the North Toutle River near Castle Lake, 13 kilometers (see appendix 2) west of the volcano. At 8:32 A.M., the volcano watchers got their wish. It was much deadlier than they could have dreamed, for the north side of the volcano collapsed. Then came the blast. A black cloud came directly from the summit and within seconds climbed over a ridge toward them. A warm wind began blowing ahead of the cloud and increased until trees bent over and branches broke; the approaching blast must have pushed air in front of it. The events of the first two minutes after the eruption were warning enough for McNerney and Smart to leave. The other people may have decided to leave a minute or two later, but it would have been too late because even McNerney and Smart barely escaped with their lives. They drove as fast as they could (up to 125 kilometers per hour on straight stretches) down a dirt road toward Highway 504 but the cloud was gaining on them. They felt the radiant heat of the cloud carried by the wind that blew into the car through the open sunroof. It felt like the car’s heater was on. After reaching the paved Highway 154, they accelerated to 140 kilometers per hour on some stretches and finally began to outdistance the cloud. When they lost sight of it, they stopped in relief, hoping that it, too, had stopped; but it soon reappeared, moving at about 72 kilometers per hour. The base of the cloud looked to them like an avalanche of black chalk dust. First, one part of the cloud shot out in front, then another, then another, like waves lapping onto a beach. What they were seeing was the turbulent front of a deadly pyroclastic flow. After pulling back onto the highway, they finally outran the cloud, at an average speed of 105 kilometers per hour.

Fig. 1-3. Before the devastating blast of Mount St. Helens on May 18, 1980, the road to the mountain was clogged by thousands of sightseers, creating a carnival atmosphere along Highway 504. Hundreds of people attempted to evade roadblocks to witness minor steam eruptions that preceded the eruption of May 18. No one had an inkling of the catastrophe that lay ahead. (Photo: Courtesy of Harry Glicken)

Fig. 1-4. The ambivalence of the authorities about the dangers of the impending eruption of Mount St. Helens is shown by the continual movement of the roadblocks that were set up to keep people away from the dangers of the volcano. The placement of the roadblocks turned out to be partly politically motivated in an attempt to protect citizens from themselves. An explanation of the chronology, which is indicated by numbers, is given in the text.

Early that morning, James Scymanky and three others were cutting wood in the valley of Hoffstadt Creek, 20 kilometers away from, and completely out of sight of, Mount St. Helens. Showing little concern about the volcano, Scymanky and two other men were felling small trees with chainsaws when a fourth man shouted that he saw a cloud appear over the ridge. Within about ten seconds came a thunderous crashing, crunching, and grinding sound from the east as trees were felled by of the blast. The men were soon engulfed by the blast cloud. The force knocked Scymanky down, and he felt a searing, painful heat on his back that lasted about two minutes. When visibility returned, the forest of small trees lay upon the ground throughout the entire valley, which was covered with 25 centimeters of gray ash. The men’s clothing remained intact, but their bodies had been extensively burned. Scymanky’s lungs were not fatally seared, and he somehow survived his bums, but the others subsequently died from theirs.

The explosion from Mount St. Helens fanned outward on the ground from the volcano in the pattern of a half circle. It had occurred as a blast that moved faster and more forcefully northward than eastward or westward. From eyewitness accounts, estimates of the cloud’s northerly velocity ranged from 496 to 510 kilometers per hour for a distance of 13 kilometers. Four parties of campers had settled near the northern boundary of destruction. They were not volcano watchers and had not camped where they could see the volcano. They were also separated from it by one or two 300-meter-high ridges. Three of these people, Dale and Leslie Davis and Albert Brooks, had stalled their pickup truck while trying to escape and the blast cloud overran them. It looked to them like a “boiling mass of rock” that picked up trees and threw them into the air. Darkness descended as the cloud surrounded them, and it became very hot in the truck cab. Chunks of rock and wood pounded the truck for a short time but, except for a small vent on the right side of the truck, the windows did not break. One of the trio received bums on both legs, just above the ankles, as ash entered the truck through the broken vent window. A brief period of light appeared a few minutes after the blast first descended upon them, but then ash fell again so densely that they could not see the truck’s hood. Nearly a half hour later, at 9 A.M., they decided to abandon the vehicle and walk, even though the darkness required that they use a flashlight. By 10:20 A.M. murky ash still kept visibility at about 10 meters. It wasn’t until later that day, after the sky had cleared, that they were rescued by helicopter.

Later examination of the truck showed that heat had deformed its plastic grill and had melted a styrofoam cooler in the truck bed. The vehicle’s right side, which had faced the volcano, had been extensively damaged—the blast had stripped its chrome trim and had sandblasted the paint.

In Miners Creek, ...

Table of contents

• Cover Page
• Title Page
• Copyright Page
• Dedication
• Contents
• Preface
• Acknowledgments
• Part I. Volcanoes and Eruptions
• Part II: The Hazards of Volcanoes
• Part III: Myths and Benefits of Volcanoes
• Part IV: Living near Volcanoes
• Appendix 1: The Volcano Traveler
• Appendix 2: Metric Conversion Table
• Index