Introduction to the special theme: Maths for Everyday Life by Jouko Vaananen and Ulrich Trottenberg Mathematics saturates everyday life more and more. It is used not only in large applications running on huge computers to predict weather or to calculate parameters for an expensive industrial process or marketing strategy: it has now become ubiquitous in the more mundane aspects of our existence. A good example is the mobile phone.
Mobile phone technology depends heavily on such fundamental areas of mathematics as analysis, algebra, and number theory. Introduction to the Special Theme Mathematics is in principle inexpensive. As the old joke says, a mathematician needs only paper, a pencil, an easy chair and a waste basket. Also, the criterion for success in mathematics is by and large universally accepted. This makes mathematics an attractive ‘investment’. Moreover, a mathematical result is valid forever.
It may fall out of fashion, or fall outside the current area of application, but even the oldest known mathematical formulae – such as that for solving quadratic equations, known 2400 years ago by Babylonians, Chinese and later the Greeks before being crystallized into its present form in 1100 AD by a Hindu mathematician called Baskhara – are the bread and butter of present-day elementary mathematics. Alas, the downside is that the results are usually not immediately applicable – and therein lies the risk.
Who wants to ‘invest’ in something that may not lead to applications for several hundred years? The good news is that the distance between theory and application is becoming shorter and shorter. Mathematics can be compared to a pyramid. On the top of the pyramid are applications of mathematics to health, weather, movies and mobile phones. However the top of this pyramid would not be so high if its base were not so wide. Only by extending the width of the base can we eventually build the top higher. This special feature of mathematics derives from its internal structure.
A good modern application of mathematics can typically draw from differential equations, numerical analysis and linear algebra. These may very well draw from graph theory, group theory and complex analysis. These in turn rest on the firm basis of number theory, topology and geometry. Going deeper and deeper into the roots of the mathematics, one ends up with such cornerstones of logic as model theory and set theory. It is clear that mathematics is heavily used in large industrial projects and in the ever-growing electronic infrastructure that surrounds us.
However, mathematics is also increasingly infiltrating smaller scale circles, such as doctors’ reception rooms, sailboat design and of course all kinds of portable devices. There has also been a change in the way mathematics penetrates our society. The oldest applications of mathematics were probably in various aspects of measurement, such as measuring area, price, length or time. This has led to tremendously successful mathematical theories of equations, dynamical systems and so on.
In today’s world, we already know pretty accurately for example the make-up of the human genome, yet we are just taking the first steps in understanding the mathematics behind this incredibly complex structure of three billion DNA base pairs. Our understanding of the mathematics of the whole universe of heavenly bodies, even going back in time to the first second of its existence, is better than our understanding of the mathematics of our own genes and bodies. What is the difference between the hereditary information encoded in DNA and the information we have about the movements of the heavenly bodies?
Is it that we have been able to encapsulate the latter into simple equations, but not the former? Or is it perhaps that the latter has a completely different nature than the former, one that makes it susceptible to study in terms of equations, while the former comes from a world governed by chance, and algorithms, a world of digital data, where the methods of the continuous world do not apply? Another well-known instance of mathematics in society is cryptography in its various guises. There exist numerous situations in which data must be encrypted such that it can be publicly transmitted without revealing the content.
On the other hand, sometimes a party may find it vitally important to break a code that another party has devised for its protection. Some companies want to examine the data of our credit card purchases in order to have access to our shopping patterns. Some governments want to do the same with regard to what they deem less innocuous patterns of behaviour. Cryptography is a typical example of the mathematics of the digital world. Digital data has become important in almost all fields of learning, a natural consequence of advances in computer technology.
This has undoubtedly influenced the way people look at fields of mathematics such as number theory, that were previously thought to be very pure and virtually devoid of applications, good or bad. Now suddenly everybody in the possession of big primes has someone looking over their shoulder. This infiltration is quite remarkable and elevates mathematics to a different position from that which it previously occupied. Mathematics is no longer a strange otherworldly subject, practised by a few curious geniuses but for most people best left alone.
The spread of microprocessors into every conceivable aspect of our everyday life has brought heavy-duty computing into our homes, into our classrooms and into scientific laboratories of all kinds. Naturally it is unnecessary for everyone to understand all this computing, which can take place in microseconds without our noticing. But it means that anyone who refuses to acknowledge the role of mathematics will see the changing technosphere as something strange and in the worst case as something irrational or even frightening.
A very good way to understand and come to terms with an important aspect of modern life – our ever-growing dependence on interpreting digital data – is to have a basic knowledge of mathematics. Basic knowledge: what does this mean and how is it attained? Clearly, this takes us into the realm of mathematics education. Strictly speaking, education is not an application of mathematics, but it is nevertheless of increasing importance to the mathematical world.
Every time the OECD’s PISA (Programme for International Students Assessment) results arrive, some people ask why some countries always seem to score highly in the mathematical skills of 15-year-olds. Without attempting to answer this difficult question, one must admit that it is important and that maths education will face huge challenges in the future, not least because of the infiltration of mathematics into all levels of society. This infiltration clearly has much to do with the revolution triggered by the development of computers over the last fifty years. Has this revolution arrived in schools, and in maths education?
Most students now own a computer with an Internet connection. This is used for games, chatting, text processing and surfing, but do they use the computer for mathematics? Are mathematical modeling (ambitious problem solving) or algorithmic thinking (expressing mathematics in such a way that the computer can handle it) taught at school? There is much that can be done here, in curricula, in textbooks and in everyday life at school. In this special issue on Mathematics for Everyday Life, we present a selection of mathematical projects that are in some way relevant, directly or indirectly, to our everyday lives.
We start with projects that have applications in the health sector and continue with the closely related topic of image processing. We then go on to the timely topic of weather (one of the prime examples of large-scale computing), the effects of which are immediately felt when the beach turns into a swamp, contrary to the weather report. We present three projects in transportation, one on ships, one on trains and one on cars. In the section on society we touch upon topics like rating, trading and immigration. We also include two articles on the topic of mathematics education.
The special issue ends with an article on a little mystery inside mathematics. Mathematics are very important in our daily lives. People use a lot of what they were taught in school without even thinking much about it. Area 1. Retiling a floor or seeding a lawn may be done by figuring the size of the area and amount of supplies needed. Percentages 2. Being able to figure out percentages can come in handy when faced with store sales or nutrition labels. Fractions 3. Road signs and recipe books have fractions, telling us the distance to our destination or how much of an ingredient to put in a dish. Addition and Subtraction 4.
Adding up the prices of groceries as you shop or calculating monthly bills requires mathematical skills. Geometry 5. Placing pictures on a wall and making certain they are hanging straight takes some knowledge of geometry. Playing the Odds 6. Some people who play the lottery use mathematical skills to try to determine the probability of their winning the jackpot. Division 7. Splitting a restaurant bill between friends uses the mathematical skill of division to determine who owes what. Two polio vaccines are used throughout the world to combat poliomyelitis (or polio). The first was developed by Jonas Salk and first tested in 1952.
Announced to the world by Salk on April 12, 1955, it consists of an injected dose of inactivated (dead) poliovirus. An oral vaccine was developed by Albert Sabin using attenuated poliovirus. Human trials of Sabin’s vaccine began in 1957 and it was licensed in 1962. [1] Because there is no long term carrier state for poliovirus in immunocompetent individuals, polioviruses have no non-primate reservoir in nature, and survival of the virus in the environment for an extended period of time appears to be remote. Therefore, interruption of person-to person transmission of the virus by vaccination is the critical step in global polio eradication. 2] The two vaccines have eradicated polio from most countries in the world,[3][4] and reduced the worldwide incidence from an estimated 350,000 cases in 1988 to 1,652 cases in 2007. [5][6][7] Development In the generic sense, vaccination works by priming the immune system with an ‘immunogen’. Stimulating immune response, via use of an infectious agent, is known as immunization. The development of immunity to polio efficiently blocks person-to-person transmission of wild poliovirus, thereby protecting both individual vaccine recipients and the wider community. 2] In 1936, Maurice Brodie, a research assistant at New York University, attempted to produce a formaldehyde-killed polio vaccine from ground-up monkey spinal cords. His initial attempts were hampered by the difficulty of obtaining enough virus. Brodie first tested the vaccine on himself and several of his assistants. He then gave the vaccine to three thousand children, many of whom developed allergic reactions, but none developed immunity to polio. [8] Philadelphia pathologist John Kolmer also claimed to have developed a vaccine that same year, but it too produced no immunity and was blamed for causing a number of cases, some of them fatal. 9] Mass polio vaccination in Columbus, Georgia during the early days of the National Polio Immunization Program. A breakthrough came in 1948 when a research group headed by John Enders at the Children’s Hospital Boston successfully cultivated the poliovirus in human tissue in the laboratory. [10] This development greatly facilitated vaccine research and ultimately allowed for the development of vaccines against polio. Enders and his colleagues, Thomas H. Weller and Frederick C. Robbins, were recognized in 1954 for their labors with a Nobel Prize in Physiology or Medicine. 11] Other important advances that led to the development of polio vaccines were: the identification of three poliovirus serotypes (Poliovirus type 1 — PV1, or Mahoney; PV2, Lansing; and PV3, Leon); the finding that prior to paralysis, the virus must be present in the blood; and the demonstration that administration of antibodies in the form of gamma-globulin protects against paralytic polio. [6][12] In 1952 and 1953, the U. S. experienced an outbreak of 58,000 and 35,000 polio cases, respectively, up from a typical number of some 20,000 a year. Amid this U. S. olio epidemic, millions of dollars were invested in finding and marketing a polio vaccine by commercial interests, including Lederle Laboratories in New York under the direction of H. R. Cox. Also working at Lederle was Polish-born virologist and immunologist Hilary Koprowski, who claims to have created the first successful polio vaccine, in 1950. His vaccine, however, being a live attenuated virus taken orally, was still in the research stage and would not be ready for use until five years after Jonas Salk’s polio vaccine (a dead injectable vaccine) had reached the market.
Koprowski’s attenuated vaccine was prepared by successive passages through the brains of Swiss albino mice. By the seventh passage, the vaccine strains could no longer infect nervous tissue or cause paralysis. After one to three further passages on rats, the vaccine was deemed safe for human use. [13][14] On February 27, 1950, Koprowski’s live, attenuated vaccine was tested for the first time on an eight year old boy from Letchworth Village, New York. The boy suffered no side effects and Koprowski enlarged his experiment to include 19 other children. 13] The development of two polio vaccines led to the first modern mass inoculations. The last cases of paralytic poliomyelitis caused by endemic transmission of wild virus in the United States occurred in 1979, with an outbreak among the Amish in several Midwest states. [15] A global effort to eradicate polio, led by the World Health Organization, UNICEF, and The Rotary Foundation, began in 1988 and has relied largely on the oral polio vaccine developed by Albert Sabin. [16] The disease was entirely eradicated in the Americas by 1994. 17] Polio was officially eradicated in 36 Western Pacific countries, including China and Australia in 2000. [18][19] Europe was declared polio-free in 2002. [20] As of 2008, polio remains endemic in only four countries: Nigeria, India, Pakistan, and Afghanistan. [5] Although poliovirus transmission has been interrupted in much of the world, transmission of wild poliovirus does continue and creates an ongoing risk for the importation of wild poliovirus into previously polio-free regions. If importations of poliovirus occurs, outbreaks of poliomyelitis may develop, especially in areas with low vaccination coverage and poor sanitation.
As a result, high levels of vaccination coverage must be maintained. [17] Inactivated vaccine Administration of the polio inoculation, including by Salk himself, in 1957 at the University of Pittsburgh where he and his team had developed the vaccine The first effective polio vaccine was developed in 1952 by Jonas Salk at the University of Pittsburgh. But it needed years of testing. To encourage patience, Salk went on CBS radio to report a successful test on a small group of adults and children on March 26, 1953; two days later the results were published in JAMA. 21] The Salk vaccine, or inactivated poliovirus vaccine (IPV), is based on three wild, virulent reference strains, Mahoney (type 1 poliovirus), MEF-1 (type 2 poliovirus), and Saukett (type 3 poliovirus), grown in a type of monkey kidney tissue culture (Vero cell line), which are then inactivated with formalin. [6] The injected Salk vaccine confers IgG-mediated immunity in the bloodstream, which prevents polio infection from progressing to viremia and protects the motor neurons, thus eliminating the risk of bulbar polio and post-polio syndrome.
In 1954, the vaccine was tested at Arsenal Elementary School and the Watson Home for Children in Pittsburgh, Pennsylvania. Salk’s vaccine was then used in a test called the Francis Field Trial, led by Thomas Francis; the largest medical experiment in history. The test began with some 4,000 children at Franklin Sherman Elementary School in McLean, Virginia, and would eventually involve 1. 8 million children, in 44 states from Maine to California. [22] By the conclusion of the study, roughly 440,000 received one or more injections of the vaccine, about 210,000 children received a placebo, consisting of harmless culture media, and 1. million children received no vaccination and served as a control group, who would then be observed to see if any contracted polio. [13] The results of the field trial were announced April 12, 1955 (the tenth anniversary of the death of Franklin D. Roosevelt; see Franklin D. Roosevelt’s paralytic illness). The Salk vaccine had been 60 – 70% effective against PV1 (poliovirus type 1), over 90% effective against PV2 and PV3, and 94% effective against the development of bulbar polio. [23] Soon after Salk’s vaccine was licensed in 1955 children’s vaccination campaigns were launched.
In the U. S, following a mass immunization campaign promoted by the March of Dimes, the annual number of polio cases fell to 5,600 by 1957. [24] By 1961 only 161 cases were recorded in the United States. [25] A Somali boy is injected with inactivated poliovirus vaccine (Mogadishu, 1993) An enhanced-potency IPV was licensed in the United States in November 1987, and is currently the vaccine of choice in the United States. [15] The first dose of polio vaccine is given shortly after birth, usually between 1–2 months of age, a second dose is given at 4 months of age. 15] The timing of the third dose depends on the vaccine formulation but should be given between 6–18 months of age. [26] A booster vaccination is given at 4 to 6 years of age, for a total of four doses at or before school entry. [27] In some countries, a fifth vaccination is given during adolescence. [26] Routine vaccination of adults (18 years of age and older) in developed countries is neither necessary nor recommended because most adults are already immune and have a very small risk of exposure to wild poliovirus in their home countries. 15] In 2002, a pentavalent (5-component) combination vaccine (called Pediarix) containing IPV was approved for use in the United States. The vaccine also contains combined diphtheria, tetanus, and acellular pertussis vaccines (DTaP) and a pediatric dose of hepatitis B vaccine. [15] In the UK, IPV is combined with tetanus, diphtheria, pertussis and Haemophilus influenzae type b vaccines. [26] When the current formulation of IPV is used, 90% or more of individuals develop protective antibody to all three serotypes of poliovirus after two doses of inactivated polio vaccine (IPV), and at least 99% are immune to poliovirus following three doses.
The duration of immunity induced by IPV is not known with certainty, although a complete series is thought to provide protection for many years. [28] Oral vaccine This 1963 poster featured CDC’s national symbol of public health, the “Wellbee”, encouraging the public to receive an oral polio vaccine. Oral polio vaccine (OPV) is a live-attenuated vaccine, produced by the passage of the virus through non-human cells at a sub-physiological temperature, which produces spontaneous mutations in the viral genome. 29] Oral polio vaccines were developed by several groups, one of which was led by Albert Sabin. Other groups, led by Hilary Koprowski and H. R. Cox, developed their own attenuated vaccine strains. In 1958, the National Institutes of Health created a special committee on live polio vaccines. The various vaccines were carefully evaluated for their ability to induce immunity to polio, while retaining a low incidence of neuropathogenicity in monkeys. Based on these results, the Sabin strains were chosen for worldwide distribution. 13] There are 57 nucleotide substitutions which distinguish the attenuated Sabin 1 strain from its virulent parent (the Mahoney serotype), two nucleotide substitutions attenuate the Sabin 2 strain, and 10 substitutions are involved in attenuating the Sabin 3 strain. [6] The primary attenuating factor common to all three Sabin vaccines is a mutation located in the virus’s internal ribosome entry site (or IRES)[30] which alters stem-loop structures, and reduces the ability of poliovirus to translate its RNA template within the host cell. 31] The attenuated poliovirus in the Sabin vaccine replicates very efficiently in the gut, the primary site of infection and replication, but is unable to replicate efficiently within nervous system tissue. OPV also proved to be superior in administration, eliminating the need for sterile syringes and making the vaccine more suitable for mass vaccination campaigns. OPV also provided longer lasting immunity than the Salk vaccine. In 1961, type 1 and 2 monovalent oral poliovirus vaccine (MOPV) was licensed, and in 1962, type 3 MOPV was licensed.
In 1963, trivalent OPV (TOPV) was licensed, and became the vaccine of choice in the United States and most other countries of the world, largely replacing the inactivated polio vaccine. [8] A second wave of mass immunizations led to a further dramatic decline in the number of polio cases. Between 1962 and 1965 about 100 million Americans (roughly 56% of the population at that time) received the Sabin vaccine. The result was a substantial reduction in the number of poliomyelitis cases, even from the much reduced levels following the introduction of the Salk vaccine. 32] OPV is usually provided in vials containing 10-20 doses of vaccine. A single dose of oral polio vaccine (usually two drops) contains 1,000,000 infectious units of Sabin 1 (effective against PV1), 100,000 infectious units of the Sabin 2 strain, and 600,000 infectious units of Sabin 3. The vaccine contains small traces of antibiotics— neomycin and streptomycin—but does not contain preservatives. [33] One dose of OPV produces immunity to all three poliovirus serotypes in approximately 50% of recipients. [15] Three doses of live-attenuated OPV produce protective antibody to all three poliovirus ypes in more than 95% of recipients. OPV produces excellent immunity in the intestine, the primary site of wild poliovirus entry, which helps prevent infection with wild virus in areas where the virus is endemic. [27] The live virus used in the vaccine is shed in the stool and can be spread to others within a community, resulting in protection against poliomyelitis even in individuals who have not been directly vaccinated. IPV produces less gastrointestinal immunity than does OPV, and primarily acts by preventing the virus from entering the nervous system.
In regions without wild poliovirus, inactivated polio vaccine is the vaccine of choice. [27] In regions with higher incidence of polio, and thus a different relative risk between efficacy and reversion of the vaccine to a virulent form, live vaccine is still used. The live virus also has stringent requirements for transport and storage, which are a problem in some hot or remote areas. As with other live-virus vaccines, immunity initiated by OPV is probably lifelong. [28] [edit] Iatrogenic (vaccine-induced) polio
A major concern about the oral polio vaccine (OPV) is its known ability to revert to a form that can achieve neurological infection and cause paralysis. [34] Clinical disease, including paralysis, caused by vaccine-derived poliovirus (VDPV) is indistinguishable from that caused by wild polioviruses. [35] This is believed to be a rare event, but outbreaks of vaccine-associated paralytic poliomyelitis (VAPP) have been reported, and tend to occur in areas of low coverage by OPV, presumably because the OPV is itself protective against the related outbreak strain. 36][37] Doses of oral polio vaccine are added to sugar cubes for use in a 1967 vaccination campaign in Bonn, Germany As the incidence of wild polio diminishes, nations transition from use of the oral vaccine back to the injected vaccine because the direct risk of iatrogenic polio (VAPP) due to OPV outweighs the indirect benefit of immunization via subclinical transmission of OPV. When IPV is used, reversion is not possible but there remains a small risk of clinical infection upon exposure to reverted OPV or wild polio virus.
Following the widespread use of polio vaccines in the mid-1950s, the incidence of poliomyelitis declined rapidly in many industrialized countries. The use of OPV was discontinued in the United States in 2000 and in 2004 in the UK, but it continues to be used around the globe. [15][26] The rate of vaccine-associated paralytic poliomyelitis (VAPP) varies by region but is generally about 1 case per 750,000 vaccine recipients. [38] VAPP is more likely to occur in adults than in children. In immunodeficient children, the risk of VAPP is almost 7,000 times higher, particularly for persons with B-lymphocyte disorders (e. g. agammaglobulinemia and hypogammaglobulinemia), which reduce the synthesis of protective antibodies. [35] The World Health Organization considers the benefits of vaccination to far outweigh the risk of vaccine derived polio. Outbreaks of vaccine derived polio have been stopped by multiple rounds of high-quality vaccination, in order to immunize the entire population. [39] Outbreaks of VAPP occurred independently in Belarus (1965–66), Canada (1966–68), Egypt (1983–1993), Hispaniola (2000–2001), Philippines (2001), Madagascar (2001–2002),[40] and in Haiti (2002), where political strife and poverty have interfered with vaccination efforts. 41] In 2006 an outbreak of vaccine-derived poliovirus occurred in China. [42] Cases have been reported from Cambodia (2005–2006), Myanmar (2006–2007), Iran (1995, 2005–2007), Syria, Kuwait and Egypt. [43] Since 2005, The World Health Organization has been tracking vaccine-caused polio in northern Nigeria caused by a mutation in live oral polio vaccines. [44] [edit] Contamination concerns In 1960, it was determined that the rhesus monkey kidney cells used to prepare the poliovirus vaccines were infected with the SV40 virus (Simian Virus-40). 45] SV40 was also discovered in 1960 and is a naturally occurring virus that infects monkeys. In 1961, SV40 was found to cause tumors in rodents. [46] More recently, the virus was found in certain forms of cancer in humans, for instance brain and bone tumors, mesotheliomas, and some types of non-Hodgkin’s lymphoma. [47][48] However, it has not been determined that SV40 causes these cancers. [49] SV40 was found to be present in stocks of the injected form of the polio vaccine (IPV) in use between 1955 to 1963. [45] It is not found in the OPV form. 45] Over 98 million Americans received one or more doses of polio vaccine between 1955 to 1963 when a proportion of vaccine was contaminated with SV40; it has been estimated that 10–30 million Americans may have received a dose of vaccine contaminated with SV40. [45] Later analysis suggested that vaccines produced by the former Soviet bloc countries until 1980, and used in the USSR, China, Japan, and several African countries, may have been contaminated; meaning hundreds of millions more may have been exposed to SV40. 50] In 1998, the National Cancer Institute undertook a large study, using cancer case information from the Institutes SEER database. The published findings from the study revealed that there was no increased incidence of cancer in persons who may have received vaccine containing SV40. [51] Another large study in Sweden examined cancer rates of 700,000 individuals who had received potentially contaminated polio vaccine as late as 1957; the study again revealed no increased cancer incidence between persons who received polio vaccines containing SV40 and those who did not. 52] The question of whether SV40 causes cancer in humans remains controversial however, and the development of improved assays for detection of SV40 in human tissues will be needed to resolve the controversy. [49] During the race to develop an oral polio vaccine several large scale human trials were undertaken. By 1958, the National Institutes of Health had determined that OPV produced using the Sabin strains were the safest. [13] Between 1957 and 1960, however, Hilary Koprowski continued to administer his vaccine around the world.
In Africa, the vaccines were administered to roughly one million people in the Belgian territories, now the Democratic Republic of the Congo, Rwanda and Burundi. [53][54] The results of these human trials have been controversial,[55] and accusations in the 1990s arose that the vaccine had created the conditions necessary for transmission of SIV from chimpanzees to humans, causing HIV/AIDS. These hypotheses have, however, been refuted. [53] By 2004, cases of poliomyelitis in Africa had been reduced to just a small number of isolated regions in the western portion of the continent, with sporadic cases elsewhere.
However, recent opposition to vaccination campaigns has evolved,[56][57] often relating to fears that the vaccine might induce sterility. [58] The disease has since resurged in Nigeria and in several other African nations, which epidemiologists believe is due to refusals by certain local populations to allow their children to receive the polio vaccine. [59] A tsunami (Japanese: ?? [ts? nami], lit. ‘harbor wave’; English pronunciation: /su?? n?? mi/ or /tsu?? n?? mi/) or tidal wave is a series of water waves (called a tsunami wave train[1]) caused by the displacement of a large volume of a body of water, such as an ocean or a large lake.
Tsunamis are a frequent occurrence in Japan; approximately 195 events have been recorded. [2] Due to the immense volumes of water and energy involved, tsunamis can devastate coastal regions. Casualties can be high because the waves move faster than humans can run. Earthquakes, volcanic eruptions and other underwater explosions (detonations of nuclear devices at sea), landslides and other mass movements, bolide impacts, and other disturbances above or below water all have the potential to generate a tsunami.
The Greek historian Thucydides was the first to relate tsunami to submarine earthquakes,[3][4] but understanding of tsunami’s nature remained slim until the 20th century and is the subject of ongoing research. Many early geological, geographical, and oceanographic texts refer to tsunamis as “seismic sea waves. ” Some meteorological conditions, such as deep depressions that cause tropical cyclones, can generate a storm surge, called a meteotsunami, which can raise tides several metres above normal levels. The displacement comes from low atmospheric pressure within the centre of the depression.
As these storm surges reach shore, they may resemble (though are not) tsunamis, inundating vast areas of land. Such a storm surge inundated Burma (Myanmar) in May 2008. Etymology The term tsunami comes from the Japanese, meaning “harbor” (tsu, ? ) and “wave” (nami, ? ). (For the plural, one can either follow ordinary English practice and add an s, or use an invariable plural as in the Japanese. [5]) Tsunami are sometimes referred to as tidal waves. In recent years, this term has fallen out of favor, especially in the scientific community, because tsunami actually have nothing to do with tides.
The once-popular term derives from their most common appearance, which is that of an extraordinarily high tidal bore. Tsunami and tides both produce waves of water that move inland, but in the case of tsunami the inland movement of water is much greater and lasts for a longer period, giving the impression of an incredibly high tide. Although the meanings of “tidal” include “resembling”[6] or “having the form or character of”[7] the tides, and the term tsunami is no more accurate because tsunami are not limited to harbours, use of the term tidal wave is discouraged by geologists and oceanographers.
There are only a few other languages that have a native word for this disastrous wave. In the Tamil language, the word is aazhi peralai. In the Acehnese language, it is ie beuna or alon buluek [8] (Depending on the dialect. Note that in the fellow Austronesian language of Tagalog, a major language in the Philippines, alon means “wave”. ) On Simeulue island, off the western coast of Sumatra in Indonesia, in the Defayan language the word is semong, while in the Sigulai language it is emong. 9] Causes Most tsunamis are generated by underwater earthquakes A tsunami can be generated when convergent or destructive plate boundaries abruptly move and vertically displace the overlying water. It is very unlikely that they can form at divergent (constructive) or conservative plate boundaries. This is because constructive or conservative boundaries do not generally disturb the vertical displacement of the water column. Subduction zone related earthquakes generate the majority of tsunami.
Tsunamis have a small amplitude (wave height) offshore, and a very long wavelength (often hundreds of kilometers long), which is why they generally pass unnoticed at sea, forming only a slight swell usually about 300 millimetres (12 in) above the normal sea surface. They grow in height when they reach shallower water, in a wave shoaling process described below. A tsunami can occur in any tidal state and even at low tide can still inundate coastal areas. On April 1, 1946, a magnitude-7. 8 (Richter Scale) earthquake occurred near the Aleutian Islands, Alaska.
It generated a tsunami which inundated Hilo on the island of Hawai’i with a 14 metres (46 ft) high surge. The area where the earthquake occurred is where the Pacific Ocean floor is subducting (or being pushed downwards) under Alaska. Examples of tsunami at locations away from convergent boundaries include Storegga about 8,000 years ago, Grand Banks 1929, Papua New Guinea 1998 (Tappin, 2001). The Grand Banks and Papua New Guinea tsunamis came from earthquakes which destabilized sediments, causing them to flow into the ocean and generate a tsunami. They dissipated before traveling transoceanic distances.
The cause of the Storegga sediment failure is unknown. Possibilities include an overloading of the sediments, an earthquake or a release of gas hydrates (methane etc. ) The 1960 Valdivia earthquake (Mw 9. 5) (19:11 hrs UTC), 1964 Alaska earthquake (Mw 9. 2), and 2004 Indian Ocean earthquake (Mw 9. 2) (00:58:53 UTC) are recent examples of powerful megathrust earthquakes that generated tsunamis (known as teletsunamis) that can cross entire oceans. Smaller (Mw 4. 2) earthquakes in Japan can trigger tsunamis (called local and regional tsunamis) that can only devastate nearby coasts, but can do so in only a few minutes.
In the 1950s, it was hypothesised[who? ] that larger tsunamis than had previously been believed possible may be caused by landslides, explosive volcanic eruptions (e. g. , Santorini and Krakatau), and impact events when they contact water. These phenomena rapidly displace large water volumes, as energy from falling debris or expansion transfers to the water at a rate faster than the water can absorb. The media dub them megatsunami. Tsunamis caused by these mechanisms, unlike the trans-oceanic tsunami, may dissipate quickly and rarely affect distant coastlines due to the small sea area affected.
These events can give rise to much larger local shock waves (solitons), such as the landslide at the head of Lituya Bay 1958, which produced a wave with an initial surge estimated at 524 metres (1,719 ft). However, an extremely large landslide might generate a megatsunami that can travel trans-oceanic distances, although there is no geological evidence to support this hypothesis. Most tsunamis are caused by submarine earthquakes which dislocate the oceanic crust, pushing water upwards. Tsunami can also be generated by erupting submarine volcanos ejecting magma into the ocean.
A gas bubble erupting in a deep part of the ocean can also trigger a tsunami Earthquake-generated tsunami An earthquake may generate a tsunami if the quake: occurs just below a body of water, is of moderate or high magnitude, and displaces a large-enough volume of water. Drawing of tectonic plate boundary before earthquake. Overriding plate bulges under strain, causing tectonic uplift. Plate slips, causing subsidence and releasing energy into water. The energy released produces tsunami waves. Characteristics When the wave enters shallow water, it slows down and its amplitude (height) increases.
The wave further slows and amplifies as it hits land. Only the largest waves crest. While everyday wind waves have a wavelength (from crest to crest) of about 100 metres (330 ft) and a height of roughly 2 metres (6. 6 ft), a tsunami in the deep ocean has a wavelength of about 200 kilometres (120 mi). Such a wave travels at well over 800 kilometres per hour (500 mph), but due to the enormous wavelength the wave oscillation at any given point takes 20 or 30 minutes to complete a cycle and has an amplitude of only about 1 metre (3. 3 ft). [10] This makes tsunamis difficult to detect over deep water.
Ships rarely notice their passage. As the tsunami approaches the coast and the waters become shallow, wave shoaling compresses the wave and its velocity slows below 80 kilometres per hour (50 mph). Its wavelength diminishes to less than 20 kilometres (12 mi) and its amplitude grows enormously, producing a distinctly visible wave. Since the wave still has such a long wavelength, the tsunami may take minutes to reach full height. Except for the very largest tsunamis, the approaching wave does not break (like a surf break), but rather appears like a fast moving tidal bore. 11] Open bays and coastlines adjacent to very deep water may shape the tsunami further into a step-like wave with a steep-breaking front. When the tsunami’s wave peak reaches the shore, the resulting temporary rise in sea level is termed run up. Run up is measured in metres above a reference sea level. [11] A large tsunami may feature multiple waves arriving over a period of hours, with significant time between the wave crests. The first wave to reach the shore may not have the highest run up. 12] About 80% of tsunamis occur in the Pacific Ocean, but are possible wherever there are large bodies of water, including lakes. They may be caused by landslides, volcanic explosions, bolides and seismic activity. Drawback If the first part of a tsunami to reach land is a trough—called a drawback—rather than a wave crest, the water along the shoreline recedes dramatically, exposing normally submerged areas. A drawback occurs because the tectonic plate on one side of the fault sinks suddenly during the earthquake, causing the overlaying water to propagate outwards with the trough of the wave at its front.
This is also why that there would not be any drawback when the tsunami travelling on the other side arrives ashore, as the tectonic plate is “raised” on that side of the fault line. Drawback begins before the wave arrives at an interval equal to half of the wave’s period. If the slope of the coastal seabed is small, drawback can exceed hundreds of meters. People unaware of the danger sometimes remain near the shore to satisfy their curiosity or to collect fish from the exposed seabed. During the Indian Ocean tsunami, the sea withdrew and many people went onto the exposed sea bed to investigate. citation needed] Photos show people walking on the normally submerged areas with the advancing wave in the background. [citation needed] Few survived. [citation needed] Scales of intensity and magnitude As with earthquakes, several attempts have been made to set up scales of tsunami intensity or magnitude to allow comparison between different events. [13] Intensity scales The first scales used routinely to measure the intensity of tsunami were the Sieberg-Ambraseys scale, used in the Mediterranean Sea and the Imamura-Iida intensity scale, used in the Pacific Ocean.
The latter scale was modified by Soloviev, who calculated the Tsunami intensity I according to the formula where Hav is the average wave height along the nearest coast. This scale, known as the Soloviev-Imamura tsunami intensity scale, is used in the global tsunami catalogues compiled by the NGDC/NOAA and the Novosibirsk Tsunami Laboratory as the main parameter for the size of the tsunami. Magnitude scales The first scale that genuinely calculated a magnitude for a tsunami, rather than an intensity at a particular location was the ML scale proposed by Murty & Loomis based on the potential energy. 13] Difficulties in calculating the potential energy of the tsunami mean that this scale is rarely used. Abe introduced the tsunami magnitude scale Mt, calculated from, where h is the maximum tsunami-wave amplitude (in m) measured by a tide gauge at a distance R from the epicenter, a, b & D are constants used to make the Mt scale match as closely as possible with the moment magnitude scale. [14] Warnings and predictions See also: Tsunami warning system One of the deep water buoys used in the DART tsunami warning system Drawbacks can serve as a brief warning.
People who observe drawback (many survivors report an accompanying sucking sound), can survive only if they immediately run for high ground or seek the upper floors of nearby buildings. In 2004, ten-year old Tilly Smith of Surrey, England, was on Maikhao beach in Phuket, Thailand with her parents and sister, and having learned about tsunamis recently in school, told her family that a tsunami might be imminent. Her parents warned others minutes before the wave arrived, saving dozens of lives. She credited her geography teacher, Andrew Kearney.
In the 2004 Indian Ocean tsunami drawback was not reported on the African coast or any other eastern coasts it reached. This was because the wave moved downwards on the eastern side of the fault line and upwards on the western side. The western pulse hit coastal Africa and other western areas. A tsunami cannot be precisely predicted, even if the magnitude and location of an earthquake is known. Geologists, oceanographers, and seismologists analyse each earthquake and based on many factors may or may not issue a tsunami warning.
However, there are some warning signs of an impending tsunami, and automated systems can provide warnings immediately after an earthquake in time to save lives. One of the most successful systems uses bottom pressure sensors that are attached to buoys. The sensors constantly monitor the pressure of the overlying water column. This is deduced through the calculation: where P = the overlying pressure in newtons per metre square, ? = the density of the seawater= 1. 1 x 103 kg/m3, g = the acceleration due to gravity= 9. 8 m/s2 and h = the height of the water column in metres.
Hence for a water column of 5,000 m depth the overlying pressure is equal to or about 5500 tonnes-force per square metre. Regions with a high tsunami risk typically use tsunami warning systems to warn the population before the wave reaches land. On the west coast of the United States, which is prone to Pacific Ocean tsunami, warning signs indicate evacuation routes. In Japan, the community is well-educated about earthquakes and tsunamis, and along the Japanese shorelines the tsunami warning signs are reminders of the natural hazards together with a network of warning sirens, typically at the top of the cliff of surroundings hills [15].
The Pacific Tsunami Warning System is based in Honolulu, Hawai? i. It monitors Pacific Ocean seismic activity. A sufficiently large earthquake magnitude and other information triggers a tsunami warning. While the subduction zones around the Pacific are seismically active, not all earthquakes generate tsunami. Computers assist in analysing the tsunami risk of every earthquake that occurs in the Pacific Ocean and the adjoining land masses. Tsunami hazard sign at Bamfield, British Columbia A tsunami warning sign on a seawall in Kamakura, Japan, 2004.
The monument to the victims of tsunami at Laupahoehoe, Hawaii Tsunami memorial in Kanyakumari beach A seawall at Tsu, Japan Tsunami Evacuation Route signage along U. S. Route 101, in Washington As a direct result of the Indian Ocean tsunami, a re-appraisal of the tsunami threat for all coastal areas is being undertaken by national governments and the United Nations Disaster Mitigation Committee. A tsunami warning system is being installed in the Indian Ocean. Computer models can predict tsunami arrival, usually within minutes of the arrival time. Bottom pressure sensors relay information in real time.
Based on these pressure readings and other seismic information and the seafloor’s shape (bathymetry) and coastal topography, the models estimate the amplitude and surge height of the approaching tsunami. All Pacific Rim countries collaborate in the Tsunami Warning System and most regularly practice evacuation and other procedures. In Japan, such preparation is mandatory for government, local authorities, emergency services and the population. Some zoologists hypothesise that some animal species have an ability to sense subsonic Rayleigh waves from an earthquake or a tsunami.
If correct, monitoring their behavior could provide advance warning of earthquakes, tsunami etc. However, the evidence is controversial and is not widely accepted. There are unsubstantiated claims about the Lisbon quake that some animals escaped to higher ground, while many other animals in the same areas drowned. The phenomenon was also noted by media sources in Sri Lanka in the 2004 Indian Ocean earthquake. [16][17] It is possible that certain animals (e. g. , elephants) may have heard the sounds of the tsunami as it approached the coast.
The elephants’ reaction was to move away from the approaching noise. By contrast, some humans went to the shore to investigate and many drowned as a result. It is not possible to prevent a tsunami. However, in some tsunami-prone countries some earthquake engineering measures have been taken to reduce the damage caused on shore. Japan built many tsunami walls of up to 4. 5 metres (15 ft) to protect populated coastal areas. Other localities have built floodgates and channels to redirect the water from incoming tsunami. However, their effectiveness has been questioned, as tsunami often overtop the barriers.
For instance, the Okushiri, Hokkaido tsunami which struck Okushiri Island of Hokkaido within two to five minutes of the earthquake on July 12, 1993 created waves as much as 30 metres (100 ft) tall—as high as a 10-story building. The port town of Aonae was completely surrounded by a tsunami wall, but the waves washed right over the wall and destroyed all the wood-framed structures in the area. The wall may have succeeded in slowing down and moderating the height of the tsunami, but it did not prevent major destruction and loss of life. 18] Natural factors such as shoreline tree cover can mitigate tsunami effects. Some locations in the path of the 2004 Indian Ocean tsunami escaped almost unscathed because trees such as coconut palms and mangroves absorbed the tsunami’s energy. In one striking example, the village of Naluvedapathy in India’s Tamil Nadu region suffered only minimal damage and few deaths because the wave broke against a forest of 80,244 trees planted along the shoreline in 2002 in a bid to enter the Guinness Book of Records. 19] Environmentalists have suggested tree planting along tsunami-prone seacoasts. Trees require years to grow to a useful size, but such plantations could offer a much cheaper and longer-lasting means of tsunami mitigation than artificial barriers. History The Samoan tsunami of September 2009 A devastated Marina beach in Chennai after the Indian Ocean Tsunami Main article: Historic tsunami At least 25 tsunami occurred in the last century. Of these, many were recorded in the Asia–Pacific region, particularly Japan. Ancient history As early as 426 B.
C. the Greek historian Thucydides inquired in his book History of the Peloponnesian War about the causes of tsunami, and was the first to argue that ocean earthquakes must be the cause. [3][4] The cause, in my opinion, of this phenomenon must be sought in the earthquake. At the point where its shock has been the most violent the sea is driven back, and suddenly recoiling with redoubled force, causes the inundation. Without an earthquake I do not see how such an accident could happen. [20] The Roman historian Ammianus Marcellinus (Res Gestae 26. 10. 5-19) described the typical sequence of a tsunami, including an incipient earthquake, the sudden retreat of the sea and a following gigantic wave, after the 365 A. D. tsunami devastated Alexandria. [21][22] 2004 Indian Ocean tsunami Main article: 2004 Indian Ocean earthquake The 2004 Indian Ocean tsunami killed over 200,000[23] people with many bodies either being lost to the sea or unidentified. According to an article in Geographical magazine (April 2008), the Indian Ocean tsunami of December 26, 2004 was not the worst that the region could expect.
Professor Costas Synolakis of the Tsunami Research Center at the University of Southern California co-authored a paper in Geophysical Journal International which suggests that a future tsunami in the Indian Ocean basin could affect locations such as Madagascar, Singapore, Somalia, Western Australia, and many others. As a weapon There have been studies and some attempt to create tsunami waves as a weapon. In World War II, the army in New Zealand trialled explosives in the area of today’s Shakespear Regional Park to create small tsunamis, an attempt which failed.
