Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 1
Extreme Waves Introduction Since you are reading this book, there is a good chance that at some time you have found yourself sitting on a beach, watching the surf—the endless progression of waves crashing on the shore. Or perhaps you have memories of walking along the shore, dancing back to keep your shoes dry as a wave expends itself, rushing up the beach. Fortunately, few of us on shore or in a boat have ever looked out to sea and seen a wave as tall as a 10-story building racing toward us, and in that instant known that there was no way to outrun it, no way to survive, and that our life was about to come to an end. Impossible? Implausible? How about a wave so high that it would wash up a mountainside higher than a 100-story building, to rip boulders and trees from the ground? Can you imagine being in a small boat and seeing that wave bearing down on you? On July 9, 1958, three boats were hit by such a wave in Lituya Bay, Alaska. Two of the boats sank, but the other one—miraculously carried out and then back into the bay by the wave—survived. There were eyewitnesses who saw this wave. They estimated that while riding the wave their boat cleared a spit of land at the entrance to the bay by 100 feet or more. The maxi-
OCR for page 2
Extreme Waves mum wave run-up, or height reached on dry land, is not an estimate; it is known exactly. The wave stripped all the trees off the mountains ringing the entrance of the bay to an elevation of 1,700 feet. This is not the largest wave ever recorded, although it is the largest wave that eyewitnesses are known to have survived. There is geologic evidence of even larger waves in prehistoric times—some caused by earthquakes, others presumed to have been caused by the impact of a meteorite in the ocean. On average, several major vessels are lost every single week somewhere in the world, many from the effects of extreme waves. Not too long ago, a major vessel was lost every day of the year. This statistic does not consider the losses of fishing boats, small boats, and pleasure craft. Peacetime ship losses are reported in six major categories: wrecked; burned; collided; foundered; missing, presumed lost; and “other.”1 “Wrecked” is the most common cause of ship loss; the term means run aground, as the result of either foul weather, equipment failure, or human error—usually navigational error. Fire or explosion is another significant cause of ship loss, due both to the cargo that ships carry and the fuel used for propulsion. Even with radar, traffic separation lanes, and radio communications, collisions still occur—in part perhaps because of the larger, faster vessels in use today—vessels that may require a mile or more to stop or change course. “Other” includes miscellaneous causes; amazingly, even today piracy accounts for ship losses. The two remaining categories are important for this book. Foundered means sunk at sea—overwhelmed by the influence of wind and wave. Vessels founder because of heavy storms, although human error (mishandling of the ship) or equipment failure (engines fail; hatches or other openings admit water into the vessel) may also contribute to a ship’s sinking. Ships also founder as a result of extreme waves—either a single large wave or several waves in quick succession—that simply overwhelm the vessel, rolling it, damaging it, or in some cases breaking it apart before the crew has time to take evasive action or even make a Mayday call on the radio.2 A wave need not be hundreds of feet high to be considered “extreme.” A wave that is 66 to 98 feet high is large
OCR for page 3
Extreme Waves enough to pose a dire threat to large vessels at sea or to structures along the coast.3 The last category—missing and presumed lost—is in my mind the most dreadful. Ships listed as missing, presumed lost are exactly that; they have suddenly disappeared, no trace of them has been found, and no reason for their sudden disappearance can be given. There are two probable causes for a ship to suddenly disappear without a radio May-day message, without launching an emergency position-indicating radio beacon, and without any survivors: a massive explosion that breaks up the vessel and causes it to sink immediately or a massive wave that overwhelms the vessel, capsizes it, and drives it and its unfortunate crew to the bottom of the ocean. Every year a number of vessels end up in the missing category. The families of crew members and the vessel owners then have to live with the agony of never knowing what really happened to loved ones, cargo, and property. Once “missing” appears on Lloyd’s Casualty List, claims can be filed and relatives can begin the mourning process.4 History tells us that in the five millennia during which humans have ventured into the sea, many have lost their lives, and ship sinkings or shipwrecks have not been uncommon. On the basis of British records for the 1700s and 1800s, noted oceanographer Willard Bascom estimated that 300,000 ships were wrecked per century. Another 100,000 per century foundered—that is, they sank in some distant ocean, away from land, usually with the loss of the entire crew.5 Bascom states that for the 10-year period 1960-1970, 2,766 major ships—500 tons and larger—were lost, an average of 277 per year. Of these, 1,136 (41 percent) were wrecked. The next largest amount, 771 (28 percent), foundered and 70 (about 2.5 percent) were declared missing. The basic data come from Lloyds and other maritime insurers. In 1980, 387 vessels were lost from a world fleet of 73,882.6 This general trend continues today. For example, for cargo vessels only—tankers, bulk carriers, and container ships—during the winters of 1997-1998 and 2004-2005, 80 and 30 vessels, respectively, were lost in a 121-day period.7 In 1997-1998 the causes and number were foundered (26), collision (22), wrecked (17), explosion/fire (14), and missing and presumed lost (1). Of those vessels that foundered, 20 incidents
OCR for page 4
Extreme Waves were caused by heavy weather and storms. In 2004-2005, the corresponding numbers were foundered (14), collision (3), wrecked (12), and explosion or fire (1). The brief reports I examined were insufficient to identify rogue waves as a specific cause, although they were indicated in several cases. For example, the container ship M/V MSC Carla broke in two during a storm in the North Atlantic, and one-half (with its 1,200 containers) sank quickly, while the other half stayed afloat and attempts were made to take it in tow and salvage it. There were two other incidents that reported a total of 86 containers lost overboard. Some of the wrecks were caused by navigational errors, but most were due to storms and foul weather. Eight of the 17 wrecks were ships grounded on Guam by Typhoon Paka in December 1999. These numbers do not include fishing boats, military vessels, passenger ships, or ferries. If commercial fishing vessels were included, the losses would double at least. The number of ships lost has decreased somewhat in the last two decades, but this is misleading, since the size of the world merchant fleet has changed. In 1980 there were 73,882 vessels, versus 39,932 in 2005. Today, the average vessel is much larger. From 1992 to 2003, a total of 1,049 merchant vessels were lost. During this time, bulk carriers (cargo vessels designed to carry grain, cement, iron ore, or similar bulk commodities) represented the greatest number of ships lost every year except 1997 and 2003. Roughly speaking, a bulk carrier or tanker was lost every other week. In 2003, 91 cargo vessels (bulk carriers, tankers, container ships, and others) exceeding 500 gross tons were lost. During 1992-2003, foundering was the major cause—30.9 percent—of all losses.8 Looking at vessel types, from 1974 to 1988, between two and three tankers per hundred suffered a serious casualty, usually resulting in an oil spill. Given that there were 5,000 to 10,000 tankers in service at these times, hundreds of vessels suffered serious casualties each year.9 During the 1992-2003 period, most of the tanker losses were caused by fire and explosion, while the majority of the bulk carrier losses (42 percent) were due to weather conditions that caused the vessel to founder or run aground. Since several major ships are lost every week and around 30 per-
OCR for page 5
Extreme Waves cent founder in heavy weather, improved design to resist extreme waves and tactics to avoid encountering them could have a measurable impact on maritime safety. Improved safety requires a better understanding of how giant waves arise. Waves change with the seasons, every year reshaping the beaches they impinge. From winter to summer the nature of a beach changes, sculpted by the tireless energy of the waves. In the winter, my beach develops a sharp drop-off, 3 to 8 feet high, as distant winter storms send breakers that carry sand out to sea. Later, other waves return the sand, and the beach returns to its characteristic slope to the sea. Usually, these changes are gradual, but sometimes, under the combined forces of a storm and an unusually high tide, the contours of the beach change dramatically overnight. The sculpting touch of the waves reveals hidden treasures. On one day, the sand might be swept bare; on the next, it might reveal a pattern of shells drawing a wavy line previously hidden from sight. Or wind and wave may combine to strand sea creatures on the shore. Once, Velella velella (by-the-wind sailor, a type of small jellyfish) appeared by the thousands along the length of my beach, their mysterious journey to find mates and to reproduce interrupted by a chance wind that blew them into the surf and left them stranded on the beach. Other sea animals know how to use the waves to their advantage, none being better adapted to the surf than the small fish called grunion. During the spring and summer months, when the grunion spawn, they wait for high tide. On several nights following the highest tide (the third, fourth, or fifth night following a full or new moon), they allow a wave to strand them on the beach, where the female scoops a shallow depression in the sand and deposits her eggs. Nearby males fertilize the eggs and then both fish wriggle their way back to the water. The eggs mature in about 10 days, but do not hatch until the next high tide washes them free of the sand and enables the hatchlings to make their way to the sea. Watching waves from the security of a sandy beach is one thing; watching them from the deck of a pitching ship is another. My intimate knowledge of waves comes from observations from the decks and cockpits of both small and large vessels. I’ve crossed the North Atlantic
OCR for page 6
Extreme Waves in December on the SS United States, 990 feet long, capacity about 2,000 passengers, which at the time was the fastest cruise ship ever built. It averaged 35.6 knots when it set the record for the crossing from Southampton to New York. I’ve also traversed the Mediterranean north to south on another cruise ship and have been in the Pacific on Cygnus Voyager, a million-barrel-capacity crude oil tanker. However, I’ve never ventured to the Southern Ocean, nor do I desire to do so. Seafarers’ lore is replete with tales of ships mysteriously disappearing or being battered by terrific wind and waves in fierce storms. It is well known that it is difficult to judge the height of a large wave accurately from the deck of a pitching ship, simply because there is no point of reference, nothing to which the eye can compare it. When eyewitness accounts can be compared to more accurate measurements, it is found that the waves are always smaller than they seem. For this reason, tales of waves 100 feet high have been discounted in the past, except in those few cases in which some type of comparative measurement has been possible. Extreme waves can arise from several different sources—tropical cyclones and storms being the most obvious cause, but possibly not the most common nor the most deadly. Large, fast-moving waves, called tsunami, can arise from undersea earthquakes or even massive landslides or the collapse of a large ice wall from a glacier. A more remote source is a meteorite striking the ocean, an event suspected to have occurred in ancient times with disastrous results. Finally, in the complex interactions that take place in the sea during which various waves from sources near and distant eventually come together—in some cases canceling each other and in other cases reinforcing each other—suddenly a wave much larger than the rest will appear. Some giant waves will disappear as quickly as they appear; others, fed by the energy of a storm, will continue to travel and grow. In either case, unlucky is the hapless vessel that finds itself in the path of such a wave. Maritime history abounds with tales of ships being lost in mysterious ways—no survivors to describe what happened, or those who survive recounting a version of events bordering on the fantastic. Extreme waves have been reported from ancient times and are mentioned by Homer (eighth century B.C.) in The Odyssey. Odysseus, after offending
OCR for page 7
Extreme Waves Poseidon, god of the seas, sees his raft destroyed by a mighty wave. In the 1500s, at the height of the Spanish conquest of South America, dozens of square-rigged galleons were lost in the Gulf of Mexico and the Gulf Stream off Florida, victims of hurricanes and extreme waves that suddenly overtook the cumbersome vessels and sent them to the bottom. In more recent times, the saga of the paddle wheel steamer Central America typifies the sinkings in those waters. Known as the “Ship of Gold,” the Central America was traveling from Panama to New York with almost 600 passengers and crew, many of them miners returning from the California gold fields. The ship transported tons of gold in the form of ingots, nuggets, gold coins, and gold dust. A number of the returning miners had made their fortunes in the gold rush and were returning east to resume less arduous lives. A week out of Panama, the ship encountered a gale. Fierce winds shredded the sails, and waves damaged the paddle wheels and steering. Water began to fill the hold, flooding and extinguishing the boilers. With no power and steerage, the vessel rolled helplessly in mammoth seas.10 When all appeared lost, another vessel—the brig Marine—appeared on the horizon. The Central America was able to evacuate women and children to the Marine, but further damage to both vessels precluded the removal of the remaining passengers. On the night of September 12, 1857, the vessel started to sink. In the horror and fear precipitated by the creaking and groaning of the dying vessel settling into the sea, one survivor recalled: The love of gold was forgotten. Men unbuckled their gold-stuffed belts and flung their hard-earned treasure on the deck, to lighten their weight. Anyone could have had a fortune, just for picking it up, but with no chance of reaching safety with this treasure.11 The Central America sank in 1,312 fathoms of water, about 173 nautical miles east of the Carolinas. Of the passengers left behind, another 50 or so were rescued, but a total of 425 died. This story has a remarkable ending. Almost to the day, 131 years later, on September 11, undersea explorer Tommy Thompson finally found “the Ship of Gold” after a search of several years. Thousands of gold coins, ingots, nuggets, and even gold dust have been recovered,
OCR for page 8
Extreme Waves along with a treasure trove of clothing and other artifacts that reveal what life in the gold fields was like. The so-called Bermuda Triangle, an area delineated by Miami, Florida; San Juan, Puerto Rico; and Bermuda, is the source of legends of mysterious disappearances of aircraft and ships. More likely, sinkings are the result of sudden weather changes that occur in the region. Storms, in combination with the strong current of the Gulf Stream, as well as sea bottom variations that range from shoals around some of the islands to some of the deepest marine trenches in the world, can combine to create large waves. The random occurrence of extreme waves—especially when the sea is not particularly rough—was previously thought to be very rare. Recent research, however, is revealing that giant waves (or rogue waves, as they are sometimes called) are more common than previously thought and are probably behind the disappearance of many vessels that have been mysteriously lost at sea. Giant waves are all the more frightening because by their very nature they can appear out of a seemingly calm sea, posing a serious risk even to supercarriers or supertankers. Some years ago I spent several weeks at the Ekofisk North Sea oil field, conducting structural tests on an offshore platform named “Two-Four-Delta.” Ekofisk is an area of the North Sea where the water depth is around 100 feet and the platform legs extend 100 feet into the seafloor. The “100-year wave”—the wave so large that it will come only once in 100 years—is the design criterion for these structures. The 100-year wave for Two-Four-Delta was 100 feet and actually came in year 2, as the platform was being constructed. Since all of the superstructure had not been installed, the platform survived with minor damage. On my visit, I spent some time on the “spider deck,” basically a series of catwalks about 30 feet above the sea. There I could observe massive steel I-beams, bent and twisted by the force of waves. It is not just ships at sea that have to be concerned with extreme waves—ports, harbors, offshore structures, coastal cities, and seaside resorts can also feel the wrath of the sea when natural forces of weather and geology become extreme. The recent December 26, 2004, magnitude 9.0 Sumatra-Andaman Islands earthquake and the resulting tsu-
OCR for page 9
Extreme Waves nami provided the latest and one of the most terrifying examples of the power of an aroused sea when pitted against human habitation. Over the centuries, tsunami have devastated coastal areas of Japan and China, where some of the oldest written records are to be found. Also, in more recent times, the destruction of huge swaths of coastal Chile and Peru are grim reminders of the power of the oceans when unleashed as huge waves. Two images always come to my mind when I think of tsunami. The first is Hilo, Hawaii, where photographs taken after the tsunami showed rows of parking meters bent over and lying parallel to the street, a silent symbol of the force of the wave that bore down on them. (See Plate 2.) The second is U.S. Coast Guard photographs of the Scotch Cap lighthouse on Unimak Island, Alaska. In the “before” photograph, the lighthouse stands tall, its beam 92 feet above the level of the sea, a rugged structure of steel-reinforced concrete. In the “after” photograph, taken a few days after a tsunami hit the lighthouse, the bluff on which the lighthouse stood is littered with debris. The lighthouse is gone, totally erased from the landscape. Also erased were the lives of the five crew members who stood watch on that fateful night. So the sea—our friend, our benefactor, vital for food, essential for transportation, critical for controlling the earth’s climate—is also a source of danger. Who would have thought that thousands of international tourists, vacationing on the sunny beaches of Indonesia and Thailand, would have but minutes to act if they were to save their lives on December 26, 2004? This frightful scenario could reoccur on other beaches at some future date. What about the millions of people living on the fringes of the world’s great oceans? With improved warning systems and education concerning tsunami dangers and evacuation procedures, many lives would be saved. And if it is true that extreme waves—waves capable of breaking and sinking major ships—are more likely to occur than previously believed, ship design standards need to be revised. These are reasons enough for everyone to understand how extreme waves are formed and propagate, and how their risks may best be managed by improved forecasting, improved warning systems, and improved design.
OCR for page 10
Extreme Waves This page intially left blank
Representative terms from entire chapter: