Here from the ground a roar like Zeus’s thunderclap
came sounding heavy round us, terrible to hear.
The horses raised their heads and pricked their ears
right up into the air, and on us fell as lively fear,
wondering what the sound could be.
And when we looked along the foaming shores,
we saw a monstrous wave towering up into the sky,
so big it took away the view of Sciron’s promontory
from my eyes. It hid the Isthmus and Asclepius’ rock.
Next, swelling up and surging onward, with, all around,
a mass of foam, and with the roaring of the sea,
it neared the shore where stood the four-horse chariot.
And in the very surge and breaking of the flood,
the wave threw up a bull, a fierce and monstrous thing,
and with his bellowing the land was wholly filled,
and fearfully re-echoed.
—EURIPIDES
Hippolytus
INCORRECTLY REFERRED TO as “tidal waves”—they have nothing to do with tides—tsunamis are among the most destructive forces in nature.* In his introduction to Douglas Myles’s book The Great Waves, George Pararas-Carayannis wrote, “The impact of tsunami [he chooses the Japanese plural, although most authors prefer “tsunamis”] on human societies can be traced back in written history to 1480 B.C. in the Eastern Mediterranean when the Minoan civilization was wiped out by such great tsunami waves generated by the volcanic explosion of the island of Santorin.” (Pararas-Carayannis’s opinions are to be taken seriously; the Greek-born seismologist is the director of the International Tsunami Information Center in Honolulu.) In Japanese, the word tsunami means “large waves in harbors,” which is another unfortunate misnomer, since most of these waves are generated deep under the open ocean, and then run up on shore. Among the currently accepted terms are “seismic sea wave,” “seismic wave disturbance,” and “oceanic shock wave,” all of which acknowledge the earthquake as the progenitor of these phenomena.
When the image of giant waves comes to mind, we usually envision great curling combers, like the 30-footers that daredevil surfers ride at places like Waimea Bay on the north shore of the Hawaiian island of Oahu. In fact, tsunamis do not look like that at all, but the popular perception is that they are gigantic, cresting, breaking waves.* Ocean waves, including the big surf of Hawaii, are generated by eastwardly moving low-pressure storms—called “extratropical cyclones” by meteorologists—that are born off the western sides of the great oceans and mature as they travel across them. The warm, light air of the low-pressure systems passes near the cool, relatively heavy air of a high, and as the air from the high rushes toward the low to equalize atmospheric pressure, wind is created, and wind creates waves. The distance over which the wind blows (known as the “fetch”), the wind velocity, and the duration of the wind directly affect the height and length of the waves. Winter storms are the largest, and thus create the largest waves. Many other factors, such as the depth of the water over which the waves form, the shape of the bottom, the slope of the shoreline, and the wind direction, affect the formation of waves. The most powerful of wind-driven waves travel at a speed of perhaps 60 miles per hour. Before they are slowed down by contact with the shelving bottom and eventually the shore, tsunamis can achieve speeds of more than 500 miles per hour—about the cruising speed of a jetliner.
The tsunami following the June 26, 1896, earthquake at Sanriku, Japan, was recorded on tide gauges in San Francisco, some five thousand miles away, ten and a half hours later, giving it an average speed of 480 miles per hour. A violent seaquake 120 miles from Japan occurred 32,000 feet down, in the Tuscarora Deep, a notorious source of seismic activity. “Such a trench,” wrote Rachel Carson, “is by its very nature a breeder of earthquakes, being a place of disturbed and uneasy equilibrium, of buckling and warping downward of the sea floor to form the deepest pits of all the earth’s surface.” At Sanriku, on the northern coast of Honshu, the seas began to recede, and in the ominous silence that followed, heads turned to watch the ocean where an impossible wall of water, 110 feet high, was bearing down. “It came at first as a far-off whisper,” wrote Michael Mooney, “similar to the sound of falling rain on water. The whisper became a hiss, then a steady rush, growing louder by the second until it reached a watery crescendo of stupefying proportions.” Millions of tons of seething, frothing water and sand engulfed the coast for hundreds of miles. More than ten thousand houses were destroyed, and as many as twenty-seven thousand people were killed.
On April 1, 1946, when residents of the town of Laupahoehoe on the eastern shore of the Big Island of Hawaii noticed that the ocean was receding, they were completely unaware of the possible consequences. After the Pacific rolled back in and then out again, many of them ventured onto the exposed wet sea floor to pick up the dead and dying fish. But a monstrous wall of water came roaring in, smashing buildings and drowning people. It receded again, but returned with even greater force, destroying almost everything in its path. It was—and still is—the largest tsunami of this century.
Often the receding of the ocean from the shore is the first sign of an approaching tsunami. In a “seaquake,” there is an abrupt collapse of a part of the ocean bed, and the sea above it drops, leaving a depression on the surface, which is filled by the surrounding waters. This leads to a wild oceanic turmoil, where the sea flows back and forth, each time higher and faster than before. The first return wave generally appears within fifteen minutes, but it might take much longer. In Waves and Beaches, oceanographer Willard Bascom described the process:
The first jolt [of three generating forces] is a simple fault in which tension in the submarine crustal rock is relieved by the abrupt rupturing of the rock along an inclined plane. When such a fault occurs, a large mass of rock drops rapidly and the support is removed from a column of water that extends to the surface. The water surface oscillates up and down as it seeks to return to mean sea level, and a series of waves is sent out. If the rock falls in compression, the mass of rock on one side rides up over that on the other, and a column of water is lifted, but the result is the same: a tsunami.
Not all deep-ocean seismic activity produces receding waters. When an island is born as a result of an underwater volcano, as with Surtsey, for example, the eruption causes land to emerge from the sea, displacing large volumes of water and generating concentric waves away from the source. Another instance in which there would be no receding is when a terrestrial event such as a landslide dumps large amounts of material into the ocean. The largest wave ever accurately measured climbed up the wooded slopes of Lituya Bay, Alaska, in 1958, when an earthquake-triggered landslide consisting of 40 million cubic yards of rock weighing some 90 million tons fell from a maximum height of 3,000 feet and crashed into the bay, sending a wall of water over a 1,740-foot-high promontory. (This is not a typographical error; the figure is one thousand seven hundred and forty feet.) That the water reached this unbelievable height was determined from the examination of trees on the slope which had been knocked down by the water. It was estimated that this monster wave—technically known as a “swash”; only when it leaves the enclosed bay and enters the sea does it begin to qualify as a tsunami—was by far the largest in recorded history. (For comparison, the Washington Monument is 555 feet high, and the Sears Tower in Chicago tops out at 1,454 feet.)
Against giant waves, there are absolutely no protective measures that can be taken, except to vacate the area. As Frank Lane has written (in The Elements Rage), “The sea defense does not exist which can repel a great tsunami; a vast wall of water, 50, 100, even 200 feet high, weighing untold millions of tons, crashing inland at 100 or even 150 mph.” Although the unfortunate victims of the Laupahoehoe tsunami were killed by the waves—there were four in all—the real killer, according to Gerard Fryer, was ignorance. Had they known what was happening, they could have evacuated the area, instead of foolishly waiting for the “tidal wave.” Tsunamis do not crest like ordinary waves, but approach the shore the way a bore does, as a wall of water with higher water behind it. True, tsunamis grow as they approach the shore—they are slowed and raised by the shoaling bottom—but even as the leading edge of the wave slows down, the vast amount of water behind it is still barreling along at speeds that can approach 500 miles per hour. This power can drive the water across half a mile of low-lying shoreline, as it did in Hawaii in 1946. Four and a half hours after the Unimak quake, the tsunami was recorded on the Honolulu tide gauges, having traveled 2,240 miles at 490 miles per hour. The water first rose eight inches in six minutes, then fell two feet in seven and a half minutes.*
Because of the unpredictable nature of tsunamis, it is rare that eyewitnesses publish detailed descriptions of these phenomena, and rarer still that an eyewitness would be an authority on the formation and character of the sea floor. In April 1946, marine geologist Francis Shepard, the author of many scientific papers, The Earth Beneath the Sea, and Submarine Canyons, was living near the beach on the north shore of Oahu when he was awakened by “a loud hissing sound, which sounded for all the world as if dozens of locomotives were blowing off steam directly outside our house.” Looking out the window, Shepard reported that “where there had been a beach previously, we saw nothing but boiling water, which was sweeping over the ten-foot top of the beach ridge and coming directly at the house.” The wall of water rolled into the house, smashed the windows, and carried the refrigerator out into a cane field. As Shepard and his wife ran for the highest ground they could see, a third wave rolled in, and then a fourth, fifth, and sixth, destroying fields, uprooting trees, and demolishing houses. As soon as possible after his harrowing ordeal, Shepard checked the literature to see if he could find anything to suggest that the waves continue to increase in size, but he found nothing. Throughout the Hawaiian Islands, but mostly on the north shore of the Big Island, 159 people were killed by this series of waves.
The source of this killer tsunami was thousands of miles from Hawaii, in the eastern Aleutian Islands. An earthquake occurred at about 2:00 a.m. on April 1, 1946, some eighty miles southeast of Unimak Island (the actual location is 53°5′ north, 163° west), where the ocean is 12,000 feet deep on the steep slope of the Aleutian Trench. At the Coast Guard station on Unimak Island, the five guardsmen in the Scotch Cap lighthouse felt a sudden, severe shudder that lasted almost a minute. Forty-seven minutes later, a series of monstrous waves thundered in and engulfed the lighthouse, shearing it off at its base and killing everyone inside. One of the waves generated by the earthquake rolled over Laupahoehoe, and hours later, another one damaged buildings, piers, and boats along the California coast. Japan, Samoa, Chile, and New Zealand all reported damage from the run-up of waves. “The entire Pacific,” wrote Fryer, “more than a third of the earth’s surface, was quivering.”
It was long assumed that the epicenter of the earthquake responsible for the Hawaiian tsunamis occurred because the Pacific Plate, subducting beneath the North Pacific Plate at the Aleutians, dragged the edge of the upper plate down, flexing it like a spring; then it snapped back, causing what is known as a “shallow-thrust earthquake.” But contemporaneous measurements of the Unimak earthquake showed that it registered 7.3 on the Richter scale, powerful enough to destroy a large city, but not great enough to have touched off such a huge tsunami. The Richter scale* measures ground motion within twenty seconds but understates the magnitude of larger earthquakes, which release most of their energy in the form of waves with longer periods (a period is the length of time required for two successive crests to pass a given point). Recent analysis has shown that the Unimak quake had a moment-magnitude reading of 8.0, making it twenty-five times more powerful than its Richter reading indicated, and therefore quite capable of generating the force necessary to launch the tsunamis. Also, the interaction of the plates might have caused a massive landslide powerful enough to initiate the deep movement of the waters that wreaked havoc on the surface. In other words, the changes in the sea floor may be more important in the development of tsunamis than the amount of seismic energy released.
One might think that a tsunami that killed 159 people in Hawaii would serve as an object lesson, and that people might have learned what to do and what not to do in the event of a receding ocean. Yet at Hilo, in May 1960, when residents were warned that a tsunami was en route across the South Pacific (as a result of a massive earthquake in Concepción, Chile, five thousand miles away), sightseers flocked to the water’s edge to watch the spectacle. They should have headed for the hills. According to one eyewitness, “The roar of the massive wall of water blended with the crashing of dozens of stores and apartments and theaters and restaurants—and with the screams of dozens of persons for whom the final noisy warning came in the same moment with death” (Lane 1965). The business district of Hilo was smashed; 282 people were injured and 61 were killed.
The 1960 Chilean earthquake, at a magnitude of 9.5 the most powerful ever recorded, is believed to have resulted from a 600-mile-long rupture of the Chilean subduction zone, which probably slipped all at once. Along 140 miles of coastline, from Puerto Saavedra to Osorno, the shoreline subsided 6 to 12 feet, leaving it open to invasion by the sea. Turbulent waves estimated at 12 to 15 feet high flooded the towns, destroyed boats and buildings, and then hissed out again, returning in a 26-foot-high wall of green water at 125 miles an hour. By the time the third and fourth waves rolled in, there was hardly anyone left, and virtually every building near the beach had been demolished. The total number of Chileans drowned will never be known, but it has been estimated at more than one thousand.
Concentric circles of waves radiated through the Pacific, flattened much of Hilo, unleashed destruction over an area of 90,000 square miles, destroyed some fifty thousand buildings, and killed six thousand people. Twenty-two hours after its inception, the quake drove a 20-foot-high wave ashore in the harbors of the Japanese islands of Honshu and Hokkaido, ten thousand miles from Chile, flinging fishing boats into dockside buildings like battering rams, killing 180 people and causing an estimated $350 million worth of damage.
We will never know what actually happened when the Aegean volcano erupted around 1500 B.C., but recent analysis of tsunamis generated by earthquake-derived movement on the sea floor suggests that it is possible to imagine a huge wall of water rolling over Crete when the island of Santorini exploded. Even without an underwater landslide, the cataclysmic explosion of a volcano can produce immense seismic waves, like the one that resulted from the eruption of Krakatau (where thirty-six thousand people were drowned by walls of water up to 135 feet high), and the eruption of the volcano in Santorini is believed to have exploded with as much as or more force than the Indonesian one. (In his 1975 article on tsunamis, Michael Mooney calls the eruption of Thera “the greatest known cataclysm in recorded history.… [E]xperts have calculated its force as four times that of Krakatoa.”)
AFTER THEY HAVE escaped the storm that sinks their ship, Dr. Pangloss and Candide make their way to Lisbon. The year, unfortunately for them, was 1755. In his 1759 novel, named for that innocent disciple of Pangloss, Voltaire wrote that “they had scarcely set foot in the town when they felt the earth tremble underneath their feet; the sea rose in foaming masses in the port and smashed the ships which rode at anchor. Whirlwinds of flame and ashes covered the streets and squares; the houses collapsed, the roofs were thrown upon the foundations, and the foundations were scattered; thirty thousand inhabitants of every age and both sexes were crushed under the ruins.” Voltaire’s description is accurate; only the number of people killed is understated.
Harry Fielding Reid wrote in 1914 of the Lisbon earthquake: “The region in which the earthquake occurred, its severity, the damage and the loss of life due to it, the distance to which it was felt, the great sea waves to which it gave rise, the agitation of the waters of distant lakes and ponds which it caused, have all united to make it the most notable earthquake of history.”* Initiated by a violent rupture of the tectonic plates that meet at the Mid-Atlantic Ridge, the Lisbon quake first shook the city—population estimated at 250,000—at 9:40 in the morning of November 1, 1755, causing churches and other tall buildings to topple, crushing hundreds in the cascading rubble. Candles that had been lit in celebration of the Mass of All Saints’ Day started fires in the churches that quickly spread to the neighboring buildings. The royal palace and other buildings were shaken from their foundations and fell on their inhabitants, but King José was spared because he was out of town. When the first tremors subsided, people ran toward the sea to escape the blistering heat of the burning city. Those who could boarded any available ship and headed away from the conflagration; others massed on the marble quay, no doubt taking solace from its massive strength. As thousands of hapless citizens watched, the sea receded in Oeiras Bay (an estuary of the Tagus River), leaving ships heeled over and fish flapping on the exposed bottom. A 50-foot wall of churning black water came roaring in, drowning the poor souls who had sought refuge away from the fires and crumbling the quay to rubble. A realistic estimate of the number of casualties is sixty thousand.
DURING THE GREAT Lisbon earthquake of 1755, buildings collapsed, fires broke out, and walls of seawater inundated the city, killing an estimated sixty thousand people, but the events did not all occur simultaneously, as shown in this nineteenth-century engraving. (illustration credit 8.1)
Because it occurred long before the introduction of the Richter scale, the magnitude of the Lisbon earthquake could not be measured, but based on its effects, it has been retroactively estimated at 8.75 to 9.0—the most violent earthquake in history until 1960, when hundreds of miles of the coast of Chile rippled. The shock waves generated by the Portuguese quake, whose epicenter is believed to have been almost directly beneath Lisbon, traveled north to England, south to Africa, and across the Atlantic to North America and the Caribbean. The Moroccan cities of Fez and Mequinez were heavily damaged, leading to speculation that there might have been another focus in North Africa, part of the same fault system. Madeira and the Canaries, islands off the northwest coast of Africa, were inundated by giant waves, and although unsubstantiated, there are stories that a 50-foot wave swamped the Andalusian port city of Cádiz.
As early as 1939, Spyridon Marinatos was suggesting that the palaces on Crete were destroyed by an earthquake that generated a giant sea wave. In “The Volcanic Destruction of Minoan Crete” (published in Antiquity), he wrote:
No historical account survives of this great earthquake, but fortunately we have an excellent means of reconstructing all the phenomena which accompanied this disaster, in the eruption of Krakatau in the Dutch East Indies on 26–27 August 1883. Geologically speaking, both volcanoes belong to the same family, and the phenomena of their eruptions are therefore analogous. The island of Krakatau is much smaller than Thera and the part of it which was submerged was about a quarter of the other (22.8 sq. km. against 83 in Thera)…. Vast quantities of pumice covered both the island and a great part of the sea round about.… A tremendous roar accompanied the explosion and was heard over 2000 miles away—just one-twelfth of the earth’s circumference.… But worst of all was a series of terrific waves which rose after the explosion. They were as much as 90 feet high, and broke with devastating force and speed against the coasts of Java and Sumatra. Where they struck a plain, they swept inland, and as far as 1000 yards inland they were still 15 yards high. Whole towns, villages and woods were destroyed, and great masses of stones from the sea were hurled far inland.… This amazing catastrophe cost over 36,000 lives.
The magnitude of the Santorini eruption is a matter of conjecture, but the largest explosion ever recorded—volcanic or otherwise—was the 1815 eruption of the volcano Tambora on the Indonesian island of Sumbawa, which is believed to have exploded with a force of 25,000 megatons, compared with the 500 megatons calculated for Krakatau. Sometime in late 1814, the mountain began to emit small showers of ash, and on the night of April 5, 1815, a strong earthquake was felt. Sir Thomas Stamford Raffles, the lieutenant governor of Java, dispatched two boats to investigate what he thought was cannon fire; and some nine hundred miles away, at Macassar on the island of Celebes, the captain of the East India Company’s Benares heard what sounded like an artillery barrage, and sailed into the Flores Sea looking for pirates. Had they correctly identified the origin of the noise, they probably would not have lived to tell about it, since it was the most powerful explosion in history. Tambora, which had been a 13,000-foot-high mountain, had blown almost a mile off its crown, covering the island with a two-foot-thick coating of ash and mud. The eruption itself killed ten thousand people. On the island of Sumbawa, boats were driven ashore as the sea rose 2 to 12 feet, then subsided. On April 10, five days after the initial explosion, a 14-foot-high wave rushed in and caused great havoc, then receded three minutes later. Subsequently, another eighty thousand people would die of famine and disease, and the ash cloud, carried around the world, cooled cities such as Geneva and New Haven to such an extent that 1816 was referred to as “the year without a summer.” It snowed in June throughout New England, and a killing frost on August 21 destroyed crops and gardens from Maine to Connecticut. In his 1994 study of earthquakes and volcanoes, Jon Erickson wrote that Tambora exploded with the equivalent of 20,000 megatons of TNT (one megaton equals 1 million tons); Krakatau exploded with 1,500 megatons; and the atomic bomb dropped on Hiroshima, with 0.02 megaton. (The eruption of the volcano in Thera in 1500 B.C. is estimated to be the second-largest explosion in history, at some 7,500 megatons.) The explosion at Tambora ejected a greater volume of matter than any other volcano, spewing some 36 cubic miles, or 1.7 million tons, of debris into the atmosphere.
BEFORE THE 1883 eruption, the Indonesian island of Krakatau looked like this. (illustration credit 8.2)
The volcano known as Krakatau* began to signal its intentions with violent earthquakes in May 1883. The island was located in the Sunda Straits, between the large islands of Sumatra and Java, and was composed of three peaks: Rakata, at 2,600 feet; Danan at 1,400; and 300-foot-high Perboewatan. (The past tense is employed when describing the island, because most of the original landmass is gone.) After three months of rumbling earth tremors, on the morning of August 27 the island blew up with a succession of blasts that could be heard three thousand miles away. (If Pikes Peak in Colorado had exploded with the same force, every person in North America would have heard it.) There were four detonations over the course of five hours; the last, occurring at 10:52 a.m., was one of the biggest explosions in history.
A hail of hot pumice fell on ships, whose officers reported a period of threatening quiet followed by a series of titanic explosions that culminated in a cloud estimated at 20 miles high. From his vantage point aboard the Sir Robert Sale, Captain W. T. Wooldridge noted that “the sky presented a most terrible appearance, a dense mass of clouds being covered with a murky tinge, with fierce flashes of lightning.” The cloud above the volcano appeared to him as “an immense pine tree, with the stem and branches formed of volcanic lightning.” An hour after the explosions, a towering cloud rose from what was left of the island, and as lightning stroboscopically lit up the blackening skies, a thick, muddy rain fell on Batavia (now Djakarta). Red-hot debris from the blast, some chunks eight feet around, fell over an area larger than France. The great discharge from the explosion created a hole in the ocean floor, and what remained of the mountain collapsed into this abyss, causing the sea to rush in. As the cold waters contacted the red-hot magma—what Frank Lane called “the titanic battle between Vulcan’s fires and Neptune’s waters”—the steam exploded with catastrophic violence, and 4 cubic miles of rock and ash were hurled into the stratosphere, some of it shooting 40 or 50 miles high. Since the island was uninhabited, nobody on Krakatau was killed, but giant tsunamis, some reaching a height of 135 feet, rolled out in all directions, flooding the coasts of Java and Sumatra, submerging more than three hundred towns and villages, and drowning more than thirty-six thousand people.
DRAWN FROM a photograph, this is the only contemporaneous illustration of the 1883 eruption of Krakatau, one of the largest and deadliest events in volcanic history. (illustration credit 8.3)
Unlike the waves that devastated Hilo, the shorelines of the Indonesian islands and bays were relatively close to the causative eruption. Hilo is more than two thousand miles from Unimak Island; some of the islands and villages affected by the sea waves when Krakatau exploded are only a couple of miles away. Calymer, the island immediately to the west of Krakatau, was completely demolished. An 87-foot-high wave engulfed and totally destroyed the town of Teluk Batung, at the head of Sumatra’s Lampong Bay, killing five thousand people. (It was here that the Dutch warship Berouw was carried over the drowned village, to come to rest more than a mile inland.) Shortly thereafter, a huge wave roared into Semanka Bay (the next embayment to the west) and overran all the villages and towns on either shore. Twenty-five hundred drowned at Beneawany, and hundreds more at Beteong, Tandjoengan, and Tanot Bringin. The water cascaded into the town of Tangerang, and when it swept out again, it carried away people, animals, houses, and trees. The death toll at Tangerang was reckoned at 1,974. To the accompaniment of thunderous explosions, the wave swept around St. Nicholas Point in Java and headed for Batavia, ninety-four miles from the epicenter. At 11:30 a.m., two hours after the initial explosion, the sea roared into the capital city. It receded, and then came back. An estimated six thousand ships, ranging in size from steamships to small proas, were destroyed in Batavia’s harbor. A reporter (quoted in Rupert Furneaux’s Krakatoa) described the scene:
To give some idea of the tidal waves which agitated the sea and rivers, we need only say that at Tanjang Priok, the water rose 10 feet within a few minutes, that it not only overflowed a portion of Lower Batavia quite suddenly, but also bore fully laden proas like straws. This phenomenon was repeated at 2 p.m. but not so violently. However great was the force exerted by this heavy flow, there came a moment, after it had raged its utmost, when the water in masses of immense height suddenly ebbing away vanished, and left the river beds and sea bottom dry.
No one knew that the waves would come back after they had receded. It is likely that many people believed the worst was over and returned to their shoreside villages, only to experience another, more catastrophic inundation. The town of Merak, which had suffered little damage from the first series of waves, was destroyed by the second and third. A 50-foot wave, traveling at hundreds of miles per hour, entered the narrow bay, and as the shoaling beach slowed down the leading edge of the wave, millions of gallons of water began piling up behind, until the wave reached the astonishing and totally terrifying height of 135 feet. This mountain of seething water rolled over poor little Merak, obliterating everyone and everything in its path. Anjer Lor was drowned by a 33-foot wave, and Tyringin, twenty-four miles from the volcano, was smashed to smithereens by a 70-foot-high locomotive of roiling water.
It was these waves, a by-product of the eruption, that caused the death and destruction. As Douglas Myles wrote, “When all the talk of Krakatoa is done and all the statistics evaluated, one salient fact remains. Despite the frightful power of the eruption itself, the emission of noxious gases, flame, smoke, volcanic bombs, and other ejecta, it was not the mountain’s fury which destroyed those unfortunate thousands, except indirectly. It was the terrible power of water. In the vast majority of instances death came at the hands of seismic sea waves.” Nine hours after the eruption, three thousand riverboats were swamped and sunk in Calcutta, two thousand miles away, and ships strained at their anchors five thousand miles distant, at Port Elizabeth, South Africa.
ANAK KRAKATAU (the “Child of Krakatau”) sends smoke and steam into the air in 1983, one hundred years after the devastating explosion of its parent, which killed more than thirty-six thousand people. (illustration credit 8.4)
Where once there had been a pretty little tropical island, there was now a hole in the ocean floor that was 1,000 feet deep and 6½ miles across. Like that of Tambora, Krakatau’s explosion generated a climate-altering ash cloud that produced lurid red, blue, green, and copper-colored sunsets and lowered temperatures around the world. What was left of Krakatau remained dormant until January 25, 1928, when a cone of basaltic rock and pumice rose out of the sea: Anak Krakatau, the “Child of Krakatau,” was born.
On December 12, 1992, as a result of a 7.5 earthquake just north of the Indonesian island of Flores, two thousand people were killed, and another two thousand injured; approximately half of these figures are attributed to tsunamis. The little village of Riangkroko was completely washed away, and every one of the 137 inhabitants was killed by a wave that was later estimated to have been 65 feet high. Two villages on the island of Babi, some three miles from the epicenter, were completely destroyed, and some of the 263 people who died were found suspended in the branches of trees. Harry Yeh et al. (1993), who visited the site seventeen days after the earthquake, opined that massive land slumps and soil liquefaction were caused by the earthquake, which produced this unexpectedly high tsunami. Less than two years later, on June 3, 1994, another earthquake occurred in the Java Trench, generating a powerful tsunami that violently struck southeast Java and extended to southwest Bali. Some two hundred people were killed, another four hundred injured, and one thousand houses destroyed. The “run-up heights” were 16 feet on Java, and 46 feet on Bali. The earthquake occurred in the ocean about 150 miles from the hardest-hit area, and there was no ground-shaking to warn the inhabitants of the impending catastrophe (Synolakis et al. 1995).
Outside the caldera of Santorini, there is a submarine promontory known as Coloumbos that erupted on September 14, 1650, and produced a steaming volcanic cone that appeared above the surface of the sea. On September 29, a violent earthquake occurred, and a huge tsunami swept over the east coast of Santorini, leaving the valleys filled with pebbles and dead fish. On the island of Ios, twenty miles away, there were waves recorded at 50 feet, and on Crete, ships were torn from their moorings and sunk in the harbor of Herakleion. When the waters receded on Santorini, remains of the ancient towns of Kamari and Perissa were revealed. The Coloumbos eruption lasted for three months, and poisonous gases killed forty people. The “island” of Coloumbos has receded beneath the surface, and the top of the cone is now 60 feet below the surface.
* There are indeed “tidal waves,” also known as “bores,” which are the sudden surges with which incoming tides arrive in some parts of the world. Among the most famous of these are the bore of Britain’s Severn River; and on the Seine, the Mascaret, which has been known to arrive at Paris as a 24-foot-high wall of water. Between New Brunswick and Nova Scotia in eastern Canada, the Bay of Fundy has the highest tides in the world, which can produce rises of 50 feet.
* Unfortunately, the dust jacket of Myles’s book, which is primarily about tsunamis, is decorated with a photograph of a curling shorebreak wave, which contradicts this important distinction. A painting by Darrel Millsap, first used on the cover of the November 1971 issue of Oceans magazine and reproduced frequently thereafter, shows a wave towering over the Scotch Cap lighthouse in the Aleutians—a gigantic comber about to break. Probably the most familiar single wave in all of art, Katsushika Hokusai’s Great Wave near Kanagawa (from his Thirty-six Views of Mount Fuji) is a very large wave indeed—it dwarfs the boats in the picture—but it is not a tsunami.
* Rarely do terrestrial landslides create tsunamis, but underwater landslides are a story of a different magnitude. In a 1995 article on tsunamis, University of Hawaii geophysicist Gerard Fryer suggests that the tsunami that overwhelmed Hilo, Hawaii, in 1946, killing 159 people and setting off the giant wave that crushed the Scotch Cap lighthouse on Unimak Island in the Aleutians, “was caused by a massive slope failure of the sedimentary wedge: a submarine landslide.… Several investigators have suggested that a similar sequence caused the Sanriku, Japan, tsunami of 1896, which killed between 22,000 and 27,000 people in Japan and wreaked massive damage in Hawaii, California and Chile.”
* The Richter scale, developed by physicist Charles Richter in 1935, is used to indicate the magnitude of earthquakes, by using a seismograph to measure the amount of energy released underground. In recent years, seismographers have switched to the “moment-magnitude scale,” which (in part) multiplies the area of the fault’s rupture surface by the distance the earth moves along the fault. The 1906 San Francisco earthquake has been estimated at 8.3 on the Richter scale and calculated at 7.7 on the M-M scale. Loma Prieta has been adjusted from 7.1 (Richter) to 7.0 (M-M), and Northridge, which was given a reading of 6.4 on the Richter, is now calibrated at 6.7 on the M-M scale.
* In terms of fatalities, the worst quake in history occurred in 1556 in Shenshu, China, where more than 830,000 people died; and again in China, the 1920 Kansu earthquake took almost 200,000 lives. In 1737, the Calcutta earthquake claimed 300,000 fatalities, and in 1923, most of Tokyo was destroyed by the great Kanto earthquake, in which 140,000 people died. The Chinese city of Tangshan was completely demolished on July 28, 1976, by two quakes, several hours apart, each of which was equivalent to the San Francisco quake of 1906. Collapsing mine tunnels under the city contributed to the disaster, in which 240,000 people died. What remained of the city was compared to the aftermath of the destruction of Hiroshima. Concerned for the safety of Beijing’s 6 million inhabitants, only eighty-five miles away, Chinese officials ordered all residents out of their houses, where they remained for two weeks.
* A Hollywood movie entitled Krakatoa, East of Java was made in 1968, a muddled story of treasure hunters foiled by the eruption of a volcano and a “tidal wave.” Unfortunately for those who named the movie, Krakatau is west of Java. When the movie was made, the volcano was popularly known as “Krakatoa,” but the spelling has now been revised to conform to the Indonesian pronunciation.