Earthquake Storms

by John Dvorak

  Chapter 2

  No Occasion for Alarm

  “You, you I want,” said the earthquake.

  “Not yet,” said San Francisco.

  —Sacramento Bee, March 1, 1904

  For centuries, the men of Anstruther, Scotland, lived most of their lives out at sea. That would have been the fate of Andrew Lawson, born in Anstruther in 1861, but his father suffered a shipwreck—an ordeal that lasted two weeks and that left his hearing impaired and his heart weakened—and Andrew’s mother took charge of the young family. She moved them to Hamilton, Ontario, for no other reason, she would say, than to prevent her son from going to sea.

  Hamilton has a peculiar feature running through it—a giant step a few hundred feet high that divides the city in half. If one follows the step, one finds that it begins in northwest New York, passes through Ontario, then swings through Michigan and Wisconsin. Known as the Niagara Escarpment, it forms the cliff over which water cascades at Niagara Falls. Geologic work has revealed that it is an erosional feature that follows the former shoreline of an ancient tropical sea. For this story, the importance of the escarpment is what is found in the vertical wall—an abundance of fossils from the Ordovician and Silurian periods—that is, from about 500 to 400 million years ago.

  These are especially well exposed in Hamilton, where one can find fossils of sponges, brachiopods, and crinoids, the last a marine animal that had a stalk and a feathery top that made it look like a miniature palm tree. Such natural oddities that are easy to collect attracted the interest of local children, and young Lawson was no exception, though in his case the fascination sent him on a lifelong journey.

  In 1883 he graduated with honors in natural science from the University of Toronto. That led immediately to a job with the Geological Survey of Canada, which assigned him to lead a field party on a survey of the Lake of the Woods region north of Lake Superior. The purpose of the survey was to decide where mineral ores might be found. The most knowledgeable geologists and the most experienced miners had already determined that such economically important deposits must exist—it was just a matter of finding them. But, true to his nature, Lawson came to challenge their most basic assessment.

  After three summers of work, following canoe routes through Lake of the Woods and studying every rocky outcrop he could find, Lawson concluded that the vast underlying mass of rock had been misidentified. And the mistake had been made by none other than Sir William Edmond Logan, the first director of the Geological Survey of Canada and the person for whom Mount Logan, the highest peak in Canada, is named.

  Logan had proclaimed the rock to be old sediments that had been altered by heat and pressure. But Lawson saw it as granite—admittedly a very old granite, one that had been deeply weathered because of its great age, but granite all the same.

  Lawson wrote his report challenging conventional opinion and his superiors blue-lined it, telling him to change major parts. Instead, he took the report to the queen’s printers and told them to publish the report as originally written. Though decades of subsequent work would show that Lawson was correct, this was not the way to advance one’s career. In 1890, Lawson resigned.

  He found work as a consulting geologist in British Columbia, hired to study the coalfields at Nanaimo next to Queen Charlotte Sound. That provided him ample opportunities to explore the nearby valleys and inlets by train and ferry. After one of these sojourns, when he returned to Vancouver, where he lived, a letter was waiting for him. It was from California and it offered him a professorship at the University of California, which then consisted of one campus located in Berkeley.

  Joseph LeConte, head of geology at the University of California and soon to be a co-founder of the Sierra Club with John Muir, never adequately explained why he hired Lawson, except to say that Lawson would teach students the science of geology while he would instruct them on the philosophical implications of the science.

  The two men had met a few years earlier at a science conference in Canada, so LeConte was probably aware of Lawson’s difficulties with his superiors. From a hint given in his later writing, it is also known that Lawson was hoping to find work and move to a warmer climate.

  California could provide that—and much more. Essentially, nothing had been done to advance knowledge of the geology of the state since Whitney and his few assistants had left and the California Geological Society had been abandoned in 1872. Almost anything Lawson chose to do would be original. And because so much of the land was well exposed, he would have the further benefit of being able to follow geologic units over long distances, something that was impossible in the heavily forested Lake of the Woods or in British Columbia.

  Lawson arrived at the university in October 1891. By the next summer, he was ready to engage in his first program of geologic research in California. He chose the Coast Ranges south of San Francisco because they were close and because, in a small corner, they contained a geologic deposit of considerable economic importance. A quicksilver mine near the southern end of San Francisco Bay that had been in operation since the beginning of the Gold Rush was the only known source of cinnabar—a mercury sulfide—in the state. Mercury was essential to extract gold from ore, so it was obvious that a component so crucial to California’s gold-mining industry should be investigated.

  Lawson enlisted the aid of a promising student, Charles Palache, to work as his field assistant. The selection was a good one: Palache would go on to be a distinguished geology professor at Harvard, and while at Harvard would assemble one of the most impressive mineral collections in the world. But for now he was a student, which meant Lawson sent him ahead to make preparations for a summer of geologic fieldwork.

  Palache procured a horse, a wagon, and supplies in San Francisco and drove the wagon to Colma, at the end of a train line that ran south of the city. On July 7, 1892, Lawson arrived by train. The next day, a Friday, the two men began what would be a momentous two weeks that ended not only in the discovery of the San Andreas Fault but, using a keen sense of geologic cunning, also led Lawson to realize that the fault had even slid recently and therefore must still be active.

  The first indication that there might be something of particular geologic interest in this region of California was the existence of a remarkably straight and deeply trenched valley that does not run parallel to the mountain ridges of the Coast Ranges but rather cuts across them. This feature is the San Andreas Valley, named by a Spanish expedition that camped within it on November 30, 1774, the feast day of the apostle known to English speakers as Saint Andrew. In the 1860s, the city of San Francisco took advantage of the large size and proximity of this extraordinary valley to pay the Spring Water Valley Company to hire more than 300 Chinese laborers to construct a dam to impound water within the valley. A long pipe was laid, and through it reservoir water was sent to San Francisco to be used by the city’s businesses and private homes and by members of the municipal fire department to fight any conflagrations.

  The San Andreas Valley is readily seen by anyone who flies into or out of San Francisco International Airport. The airport is located on what was once a marshy plain at the edge of San Francisco Bay. To the north is an isolated block that forms San Bruno Mountain. Colma is immediately west of the block. Three miles south of Colma is where the San Andreas Valley begins.

  The water reservoir lies along the axis of the valley. If one projects the axis northward, it intersects the Pacific coast at Mussel Rock. It was here that Lawson and Palache found the next piece of evidence that drew their attention to the importance of the valley.

  For the next few days, they did reconnaissance work along a wagon road that ran from Colma to the coast. North of Mussel Rock they found a thick section of loose marine sediments; from Mussel Rock south was a system of hard rocks—greenstones and granites. Such a juxtaposition of different rock types always piques a geologist’s interest and cries out for explanation. After just a single day, L
awson and Palache could provide one.

  On the morning of Wednesday, July 13, Lawson and Palache took a stroll, one that can be easily replicated today, along the long stretch of sandy beach north of Mussel Rock, outlined on the landward side by a high sea cliff. I suggest making the descent to the beach at Thornton Beach State Park, a popular site for paragliders, in Daly City. From there, one heads south.

  The layered marine sediments exposed in the sea cliff are rocks of the Merced Formation—named by Lawson—comprised, as he wrote in his field notebook, of a “fine section of fossiliferous sandy clays, soft sandstones, and shell beds cemented hard.” What is important here is how much these sedimentary beds, originally laid down as horizontal layers, have been tilted and now deviate from a horizontal line.

  For the first few miles south of Thornton Beach, the beds of the Merced Formation are nearly horizontal, but that changes as one nears Mussel Rock.

  As Lawson recorded in his notebook, within a quarter mile of Mussel Rock (the haystack-shaped greenstone sentinel that sits just off the coast in the zone of breakers), the beds of the Merced Formation are tilted at various angles, some as steep as 65 degrees. Soon after, he offered an explanation, declaring that “a great fault” existed between the soft rocks of the Merced Formation and the hard greenstones and granites south of Mussel Rock, and it was movement along this fault that had caused the normally horizontal beds of the Merced Formation to become jumbled. Furthermore, it was no coincidence that Mussel Rock lay along a projection of the axis of the San Andreas Valley; in fact, the fault probably extended along the length of the valley, a distance of 40 miles. And it was this association that led Lawson to give it a name, the San Andreas Fault, the name first used in a government report prepared by Lawson and published in 1895 that described the geology of the San Francisco peninsula. But it was long before this that Palache made a key observation that quickly led Lawson to conclude that the San Andreas Fault had recently moved.

  The day after they strolled on the beach, Lawson left Palache alone for a few days while he returned to San Francisco and Berkeley to attend university meetings and to conduct university business. But he gave his student instructions: Lawson wanted Palache to search for outcrops of rocks that might exist on the east side of the newly discovered fault.

  Palache did as he was told. On July 20, he began at the edge of the sea cliff in what is today the Westlake District of Daly City. There the deeply soil-covered surface was planted in vast fields of cabbage cultivated right up to the edge of the cliff. Palache rode his horse through the fields, then through pastures where cows grazed. He was unable to find any outcrops, but he did find something curious.

  Little ponds were sometimes midway up a slope or atop ridges, in places that seemed unlikely for ponds to exist. They were long and narrow and had neither outlets nor streams feeding them. Most curious of all, they were strung along a long line.

  Palache was puzzled by them but saw no special significance in their form and location. He of course mentioned them to Lawson the next day and was surprised when the professor became excited and insisted that he be shown the ponds at once.

  None of the ponds exist today, though by using old maps a few of the depressions where the ponds once lay can be located. Some are now small community parks, such as Imperial Park in Pacifica and Callan Park in South San Francisco. One of the largest ponds has been filled and a softball field built over it at what is today an athletic complex known as Fairmont Park, also in Pacifica. One wonders, watching players hit balls and race around the bases, whether any of them knows what lurks beneath the ground.

  Lawson knew. And he realized this not because of what he saw but because of what he did not see.

  Geology is about sleuthing. And to be a good field geologist is to be an exceptional detective. Here one is reminded of the famous Sherlock Holmes mystery “The Adventure of Silver Blaze” in which the crucial clue is a watchdog that did not bark—a story, by interesting coincidence, first published in December 1892, a few months after Lawson discovered and first studied the San Andreas Fault. And what Lawson did not see along the line of small ponds in 1892 was the geologic equivalent of not hearing a dog bark.

  The land west and south of San Francisco was still mostly vacant in the 1890s, much of it covered by sand dunes that shifted during strong ocean breezes. As the sand shifted, some of it would get caught in and fill depressions. The fact that several small ponds existed in a small area near the coast west of Colma was evidence that the depressions that held those ponds must have formed recently.**** Thus, because these particular ponds lined up along an extension of the San Andreas Valley where Lawson just a week earlier had determined a fault existed, from the alignment of ponds and, hence, from the alignment of depressions, he concluded “movement along this fault zone is still in progress.”

  And, indeed, it is.

  But Lawson left out an element that we would consider essential today: Does the segment of the San Andreas Fault that he discovered in 1892 represent a seismic risk?

  The question probably did not even occur to him. The idea that the slippage of geologic faults was the cause of earthquakes had been proposed only eight years earlier—by Gilbert, after his study of the 1872 Owens Valley earthquake—and it was an idea that was not yet widely accepted. How Lawson felt about the matter goes unrecorded, because few geologists—Gilbert being an exception—considered it relevant to their science.

  In fact, the scientific study of earthquakes had begun only a few decades earlier, and that study was not undertaken by someone even remotely connected to geology. Instead, initially it was pursued by a man who had a more practical concern—the construction of buildings.

  Robert Mallet, an Irish engineer, became interested in earthquakes because of a diagram he saw in Principles of Geology, first published in 1830 and written by Charles Lyell—the same man who influenced Whitney—that showed how the passage of waves of a large earthquake in Italy in 1783 had caused heavy stones stacked to form a tall obelisk to rotate. Lyell gave this as evidence that, in addition to the back-and-forth and up-and-down motions of an earthquake, there was also a rotational, or “vorticose” one. Mallet, an accomplished designer and builder of major structures—his constructions include the terminal station of the Dublin and Drogheda Railway, a large polygonal shed with a giant hydraulic turntable at the center; a series of swivel bridges across the River Shannon; the Westminster Bridge in London; the Fastnet Rock lighthouse that stands on the southernmost point of Ireland and thus was the last part of Ireland seen by emigrants sailing to the United States—was well practiced in the art of moving and positioning heavy objects, so he knew that a stone could be rotated simply by applying an appropriately directed force.

  A rotation came about if the geometric center of the base of a heavy stone did not lie directly beneath the center of gravity of the stone. From the diagram shown by Lyell, Mallet saw that was the case for the stones that formed the obelisk.

  That simple realization led him on a lifelong quest to understand earthquakes based on his practical knowledge of mechanics. In 1857, with letters of support from Charles Lyell and from Charles Darwin, he received funds from the Royal Society of London to go to Italy and study the devastating effects of a recent earthquake.

  At first, he admitted, he found himself “in the midst of utter confusion.” But with the practiced eye of an engineer, he soon saw a pattern to the destruction. There was a central area, measuring a few miles across, where almost every building had collapsed and where there had been the greatest loss of life. Beyond this was a much larger area where many people had been injured and where many, though not all, buildings had collapsed. He identified a third area, larger still, where a few buildings had fallen and where there had been almost no loss of life. And there was a fourth area, extending for hundreds of miles beyond the central area, where almost everyone had felt the earthquake but there was little to no visible dam
age.

  What he produced was the first isoseismal map of an earthquake, something that is now routine and used by engineers to gauge the level of destruction and by scientists to estimate the intensity of an earthquake.

  Mallet also had a considerable knowledge of explosives. His expertise was so well regarded that in 1835 when the water well used by Guinness and Company in Dublin to produce its ale gave out, Mallet was hired to restore it. He did so by boring a three-inch-diameter hole deep into the solid rock at the base of the well, then packing the hole with gunpowder and exploding it. The shock shattered enough rock that the well has never been dry since.

  Mallet now applied his knowledge of explosives to determine the speed of seismic waves. He began by burying 25 pounds of gunpowder at a sandy beach in Dublin County. Then, from half a mile away, he watched. When the gunpowder exploded, he turned his attention to a saucer filled with mercury, recording how long it took for the first ripples to appear. From this beginning, his experiments grew to 12,000 pounds of gunpowder exploded at a rock quarry in Wales. Eventually he concluded—and it was the first time anyone had done so—that waves produced by earthquakes travel at speeds of more than a mile a second through the Earth, a phenomenal rate when one considers that the fastest mode of transportation of the era was by train, which then traveled at speeds of no more than a few miles per hour.

  In 1852 he felt his first earthquake, which he remembered as a “heavy thump” that woke him from sleep and which he did not realize was an earthquake—initially, he thought it was a burglar breaking into his house—until he talked to neighbors the next morning. Probably of no connection to this singular event, the same year, Mallet began his greatest undertaking—to compile a catalogue of all major earthquakes that had occurred in history.