A tsunami or tidal wave known as a seismic sea wave, is a series of waves in a water body caused by the displacement of a large volume of water in an ocean or a large lake. Earthquakes, volcanic eruptions and other underwater explosions above or below water all have the potential to generate a tsunami. Unlike normal ocean waves, which are generated by wind, or tides, which are generated by the gravitational pull of the Moon and the Sun, a tsunami is generated by the displacement of water. Tsunami waves do not resemble normal undersea currents or sea waves because their wavelength is far longer. Rather than appearing as a breaking wave, a tsunami may instead resemble a rising tide. For this reason, it is referred to as a "tidal wave", although this usage is not favoured by the scientific community because it might give the false impression of a causal relationship between tides and tsunamis. Tsunamis consist of a series of waves, with periods ranging from minutes to hours, arriving in a so-called "internal wave train".
Wave heights of tens of metres can be generated by large events. Although the impact of tsunamis is limited to coastal areas, their destructive power can be enormous, they can affect entire ocean basins; the 2004 Indian Ocean tsunami was among the deadliest natural disasters in human history, with at least 230,000 people killed or missing in 14 countries bordering the Indian Ocean. The Ancient Greek historian Thucydides suggested in his 5th century BC History of the Peloponnesian War that tsunamis were related to submarine earthquakes, but the understanding of tsunamis remained slim until the 20th century and much remains unknown. Major areas of current research include determining why some large earthquakes do not generate tsunamis while other smaller ones do; the term "tsunami" is a borrowing from the Japanese tsunami 津波, meaning "harbour wave". For the plural, one can either follow ordinary English practice and add an s, or use an invariable plural as in the Japanese; some English speakers alter the word's initial /ts/ to an /s/ by dropping the "t", since English does not natively permit /ts/ at the beginning of words, though the original Japanese pronunciation is /ts/.
Tsunamis are sometimes referred to as tidal waves. This once-popular term derives from the most common appearance of a tsunami, that of an extraordinarily high tidal bore. Tsunamis and tides both produce waves of water that move inland, but in the case of a tsunami, the inland movement of water may be much greater, giving the impression of an high and forceful tide. In recent years, the term "tidal wave" has fallen out of favour in the scientific community, because the causes of tsunamis have nothing to do with those of tides, which are produced by the gravitational pull of the moon and sun rather than the displacement of water. Although the meanings of "tidal" include "resembling" or "having the form or character of" the tides, use of the term tidal wave is discouraged by geologists and oceanographers. A 1969 episode of Hawaii Five-O entitled "Forty Feet High And It Kills!" used the terms "tsunami" and "tidal wave" interchangeably. The term seismic sea wave is used to refer to the phenomenon, because the waves most are generated by seismic activity such as earthquakes.
Prior to the rise of the use of the term tsunami in English, scientists encouraged the use of the term seismic sea wave rather than tidal wave. However, like tsunami, seismic sea wave is not a accurate term, as forces other than earthquakes – including underwater landslides, volcanic eruptions, underwater explosions, land or ice slumping into the ocean, meteorite impacts, the weather when the atmospheric pressure changes rapidly – can generate such waves by displacing water. While Japan may have the longest recorded history of tsunamis, the sheer destruction caused by the 2004 Indian Ocean earthquake and tsunami event mark it as the most devastating of its kind in modern times, killing around 230,000 people; the Sumatran region is accustomed to tsunamis, with earthquakes of varying magnitudes occurring off the coast of the island. Tsunamis are an underestimated hazard in the Mediterranean Sea and parts of Europe. Of historical and current importance are the 1755 Lisbon earthquake and tsunami, the 1783 Calabrian earthquakes, each causing several tens of thousands of deaths and the 1908 Messina earthquake and tsunami.
The tsunami claimed more than 123,000 lives in Sicily and Calabria and is among the most deadly natural disasters in modern Europe. The Storegga Slide in the Norwegian Sea and some examples of tsunamis affecting the British Isles refer to landslide and meteotsunamis predominantly and less to earthquake-induced waves; as early as 426 BC the Greek historian Thucydides inquired in his book History of the Peloponnesian War about the causes of tsunami, was the first to argue that ocean earthquakes must be the cause. 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, recoiling with redoubled force, causes the inundation. Without an earthquake I do not see; the Roman historian Ammianus Marcellinus described the typical sequence of a tsunami, including an incipient earthquake, the sudden retreat of the sea and a followin
Matthew C. Perry
Matthew Calbraith Perry was a Commodore of the United States Navy who commanded ships in several wars, including the War of 1812 and the Mexican–American War. He played a leading role in the opening of Japan to the West with the Convention of Kanagawa in 1854. Perry was interested in the education of naval officers, assisted in the development of an apprentice system that helped establish the curriculum at the United States Naval Academy. With the advent of the steam engine, he became a leading advocate of modernizing the U. S. Navy and came to be considered "The Father of the Steam Navy" in the United States. Matthew Perry was the son of Navy Captain Christopher Raymond Perry, he was born April 10, 1794, South Kingstown, R. I. U. S, his siblings included Oliver Hazard Perry, Raymond Henry Jones Perry, Sarah Wallace Perry, Anna Marie Perry, James Alexander Perry, Nathaniel Hazard Perry, Jane Tweedy Perry. His mother was born in County Down and was a descendant of an uncle of William Wallace, the Scottish knight and landowner, known for leading a resistance during the Wars of Scottish Independence and is today remembered as a patriot and national hero.
His paternal grandparents were James Freeman Perry, a surgeon, Mercy Hazard, a descendant of Governor Thomas Prence, a co-founder of Eastham, a political leader in both the Plymouth and Massachusetts Bay colonies, governor of Plymouth. In 1809, Perry received a midshipman's warrant in the Navy, was assigned to USS Revenge, under the command of his elder brother, his early career saw him assigned to several ships, including USS President, where he served as an aide to Commodore John Rodgers. President was in a victorious engagement over a British vessel, HMS Little Belt, shortly before the War of 1812 was declared. Perry continued aboard President during the War of 1812 and was present at the engagement with HMS Belvidera. Rodgers fired the first shot of the war at Belvidera. A shot resulted in a cannon bursting, killing several men and wounding Rodgers and others. Perry transferred to USS United States, commanded by Stephen Decatur, saw little fighting in the war afterwards, since the ship was trapped in port at New London, Connecticut.
Following the signing of the Treaty of Ghent, which ended the war, Perry served on various vessels in the Mediterranean. Perry served under Commodore William Bainbridge during the Second Barbary War, he served in African waters aboard USS Cyane during its patrol off Liberia from 1819 to 1820. After that cruise, Perry was sent to suppress the slave trade in the West Indies. During this period, while in port in Russia, Perry was offered a commission in the Imperial Russian Navy, which he declined. Perry commanded USS Shark, a schooner with 12 guns, from 1821 to 1825. In 1763, when Britain possessed Florida, the Spanish contended that the Florida Keys were part of Cuba and North Havana. Certain elements within the United States felt that Key West could be the "Gibraltar of the West" because it guarded the northern edge of the 90 miles wide Straits of Florida—the deep water route between the Atlantic and the Gulf of Mexico. In 1815 the Spanish governor in Havana deeded the island of Key West to Juan Pablo Salas of Saint Augustine.
After Florida was transferred to the United States, Salas sold Key West to American businessman John W. Simonton for $2,000 in 1821. Simonton lobbied the U. S. Government to establish a naval base on Key West both to take advantage of its strategic location and to bring law and order to the area. On March 25, 1822, Perry sailed Shark to Key West and planted the U. S. flag, physically claiming the Keys as United States territory. Perry renamed Cayo Hueso "Thompson's Island" for the Secretary of the Navy Smith Thompson and the harbor "Port Rodgers" for the president of the Board of Navy Commissioners. Neither name stuck however. From 1826 to 1827, Perry acted as fleet captain for Commodore Rodgers. Perry returned to Charleston, South Carolina for shore duty in 1828, in 1830 took command of a sloop-of-war, USS Concord, he spent the years 1833–1837 as second officer of the New York Navy Yard, gaining promotion to captain at the end of this tour. Perry had an ardent interest and saw the need for the naval education, supporting an apprentice system to train new seamen, helped establish the curriculum for the United States Naval Academy.
He was a vocal proponent of modernizing the Navy. Once promoted to captain, he oversaw construction of the Navy's second steam frigate USS Fulton, which he commanded after its completion, he was called "The Father of the Steam Navy", he organized America's first corps of naval engineers, conducted the first U. S. naval gunnery school while commanding Fulton in 1839–1841 off Sandy Hook on the coast of New Jersey. Perry received the title of commodore in June 1840, when the Secretary of the Navy appointed him commandant of New York Navy Yard; the United States Navy did not have ranks higher than captain until 1857, so the title of commodore carried considerable importance. An officer would revert to his permanent rank after the squadron command assignment had ended, although in practice officers who received the title of commodore retained the title for life, Perry was no exception. During his tenure in Brooklyn
The Bonin Islands known as the Ogasawara Islands, or, Yslas del Arzobispo, are an archipelago of over 30 subtropical and tropical islands, some 1,000 kilometres directly south of Tokyo, Japan. The name "Bonin Islands" comes from the Japanese word bunin, meaning "no people" or "uninhabited"; the only inhabited islands of the group are Chichijima, the seat of the municipal government, Hahajima. Ogasawara Municipality and Ogasawara Subprefecture take their names from the Ogasawara Group. Ogasawara Archipelago is used as a wider collective term that includes other islands in Ogasawara Municipality, such as the Volcano Islands, along with three other remote islands. Geographically speaking, all of these islands are part of the Nanpō Islands. A total population of 2,440, 2,000 on Chichijima and 440 on Hahajima, lives in the Ogasawara Group, which has a total area of 84 square kilometres; because the Ogasawara Islands have never been connected to a continent, many of their animals and plants have undergone unique evolutionary processes.
This has led to the islands' nickname of "The Galápagos of the Orient", their nomination as a natural World Heritage Site on June 24, 2011. The giant squid was photographed off the Ogasawara Islands for the first time in the wild on 30 September 2004, was filmed alive in December 2006. A 25-meter-diameter radio telescope is located in Chichijima, one of the stations of the very-long-baseline interferometry Exploration of Radio Astrometry project, is operated by the National Astronomical Observatory of Japan; the Bonin Islands consist of three subgroups, which are listed below along with their main islands: Muko-jima Group – Parry Group: Muko-jima. Geographically, they are not traditionally considered part of the Bonin Islands, which are the Mukojima and Hahajima island clusters. In other words, the historical range of the Bonin Islands is not the precise equivalent of the Japanese governmental unit; the Bonin Islands is a geographical term excluding the other islands which are today associated within the boundaries of a collective term, Ogasawara Shotō.
Prehistoric tools and carved stones, discovered on North Iwo Jima at the end of the 20th century, as well as stone tools discovered on Chichi-jima, indicate the islands might have been populated in ancient times. The first recorded visit by Europeans to the islands happened on 2 October 1543, when the Spanish explorer Bernardo de la Torre on the San Juan sighted Haha-jima, which he charted as Forfana. At that time, the islands were not populated. Japanese discovery of the islands occurred in Kanbun 10 and was followed by a shogunate expedition in Enpō 3; the islands were referred to as Bunin jima "the uninhabited islands". Shimaya Ichizaemon, the explorer at the order of the shogunate, inventoried several species of trees and birds, but after his expedition, the shogunate abandoned any plans to develop the remote islands. In 1727, Ogasawara Sadatō, a rōnin, claimed that the islands were discovered by his ancestor Ogasawara Sadayori, in 1593, the territory was granted as a fief by Toyotomi Hideyoshi.
However, investigation of the claim found that it was a fraud and the existence of Sadayori was doubtful. The first published description of the islands in the West was brought to Europe by Isaac Titsingh in 1796, his small library of Japanese books included Sangoku Tsūran Zusetsu by Hayashi Shihei. This book, published in Japan in 1785 described the Ogasawara Islands; these groups were collectively called Islas del Arzobispo in Spanish sources of the 18th–19th century. This name is most due to an expedition organized by the Arzobispo Pedro Moya de Contreras, Viceroy of New Spain, to explore the northern Pacific and the islands of Japan, its main objective was to find the long sought and legendary islands of Rica de Oro, Rica de Plata and the Islas del Armenio. After several years of planning and frustrated attempts the expedition set sail on 12 July 1587 c
Hirohito was the 124th Emperor of Japan according to the traditional order of succession, reigning from 25 December 1926, until his death on 7 January 1989. He was succeeded by Akihito. In Japan, reigning emperors are known as "the Emperor" and he is now referred to by his posthumous name, Emperor Shōwa; the word Shōwa is the name of the era coinciding with the Emperor's reign, after which he is known according to a tradition dating to 1912. The name Hirohito means "abundant benevolence". At the start of his reign, Japan was one of the great powers—the ninth-largest economy in the world, the third-largest naval power, one of the four permanent members of the council of the League of Nations, he was the head of state under the Constitution of the Empire of Japan during Japan's imperial expansion and involvement in World War II. After Japan's surrender, he was not prosecuted for war crimes as many other leading government figures were, his degree of involvement in wartime decisions remains controversial.
During the post-war period, he became the symbol of the new state under the post-war constitution and Japan's recovery, by the end of his reign, Japan had emerged as the world's second largest economy. Born in Tokyo's Aoyama Palace on 29 April 1901, Hirohito was the first son of 21-year old Crown Prince Yoshihito and 17-year old Crown Princess Sadako, he was the grandson of Yanagihara Naruko. His childhood title was Prince Michi. On the 70th day after his birth, Hirohito was removed from the court and placed in the care of the family of Count Kawamura Sumiyoshi, a former vice-admiral, to rear him as if he were his own grandchild. At the age of 3, Hirohito and his brother Chichibu were returned to court when Kawamura died – first to the imperial mansion in Numazu, Shizuoka back to the Aoyama Palace. In 1908, he began elementary studies at the Gakushūin; when his grandfather, Emperor Meiji, died on 30 July 1912, Hirohito's father, assumed the throne and Hirohito became the heir apparent. At the same time, he was formally commissioned in both the army and navy as a second lieutenant and ensign and was decorated with the Grand Cordon of the Order of the Chrysanthemum.
In 1914, he was promoted to the ranks of lieutenant in the army and sub-lieutenant in the navy to captain and lieutenant in 1916. He was formally proclaimed Crown Prince and heir apparent on 2 November 1916. Hirohito attended Gakushūin Peers' School from 1908 to 1914 and a special institute for the crown prince from 1914 to 1921. In 1920, Hirohito was promoted to the rank of Major in the army and Lieutenant Commander in the navy. In 1921, Hirohito took a six-month tour of Western Europe, including the United Kingdom, Italy, the Netherlands, Belgium. After his return to Japan, Hirohito became Regent of Japan on 29 November 1921, in place of his ailing father, affected by a mental illness. In 1923, he was promoted to the rank of Lieutenant-Colonel in the army and Commander in the navy, to army Colonel and Navy Captain in 1925. During Hirohito's regency, a number of important events occurred: In the Four-Power Treaty on Insular Possessions signed on 13 December 1921, the United States and France agreed to recognize the status quo in the Pacific, Japan and Britain agreed to terminate formally the Anglo-Japanese Alliance.
The Washington Naval Treaty was signed on 6 February 1922. Japan withdrew troops from the Siberian Intervention on 28 August 1922; the Great Kantō earthquake devastated Tokyo on 1 September 1923. On 27 December 1923, Daisuke Namba attempted to assassinate Hirohito in the Toranomon Incident but his attempt failed. During interrogation, he claimed to be a communist and was executed but some have suggested that he was in contact with the Nagacho faction in the Army. Prince Hirohito married his distant cousin Princess Nagako Kuni, the eldest daughter of Prince Kuniyoshi Kuni, on 26 January 1924, they had five daughters. The daughters who lived to adulthood left the imperial family as a result of the American reforms of the Japanese imperial household in October 1947 or under the terms of the Imperial Household Law at the moment of their subsequent marriages. On 25 December 1926, Hirohito assumed the throne upon Yoshihito's, death; the Crown Prince was said to have received the succession. The Taishō era's end and the Shōwa era's beginning were proclaimed.
The deceased Emperor was posthumously renamed Emperor Taishō within days. Following Japanese custom, the new Emperor was never referred to by his given name, but rather was referred to as "His Majesty the Emperor", which may be shortened to "His Majesty". In writing, the Emperor was referred to formally as "The Reigning Emperor". In November 1928, the Emperor's ascension was confirmed in ceremonies which are conventionally identified as "enthronement" and "coronation"; the first part of Hirohito's reign took plac
An island or isle is any piece of sub-continental land, surrounded by water. Small islands such as emergent land features on atolls can be called islets, cays or keys. An island in a river or a lake island may be called an eyot or ait, a small island off the coast may be called a holm. A grouping of geographically or geologically related islands is called an archipelago, such as the Philippines. An island may be described despite the presence of an artificial land bridge; some places may retain "island" in their names for historical reasons after being connected to a larger landmass by a land bridge or landfill, such as Coney Island and Coronado Island, though these are speaking, tied islands. Conversely, when a piece of land is separated from the mainland by a man-made canal, for example the Peloponnese by the Corinth Canal or Marble Hill in northern Manhattan during the time between the building of the United States Ship Canal and the filling-in of the Harlem River which surrounded the area, it is not considered an island.
There are two main types of islands in the sea: oceanic. There are artificial islands; the word island derives from Middle English iland, from Old English igland. However, the spelling of the word was modified in the 15th century because of a false etymology caused by an incorrect association with the etymologically unrelated Old French loanword isle, which itself comes from the Latin word insula. Old English ieg is a cognate of Swedish ö and German Aue, related to Latin aqua. Greenland is the world's largest island, with an area of over 2.1 million km2, while Australia, the world's smallest continent, has an area of 7.6 million km2, but there is no standard of size that distinguishes islands from continents, or from islets. There is a difference between continents in terms of geology. Continents are the largest landmass of a particular continental plate. By contrast, islands are either extensions of the oceanic crust, or belong to a continental plate containing a larger landmass. Continental islands are bodies of land.
Examples are Borneo, Sumatra, Sakhalin and Hainan off Asia. A special type of continental island is the microcontinental island, created when a continent is rifted. Examples are Madagascar and Socotra off Africa, New Caledonia, New Zealand, some of the Seychelles. Another subtype is an island or bar formed by deposition of tiny rocks where water current loses some of its carrying capacity; this includes: barrier islands, which are accumulations of sand deposited by sea currents on the continental shelves fluvial or alluvial islands formed in river deltas or midstream within large rivers. While some are transitory and may disappear if the volume or speed of the current changes, others are stable and long-lived. Islets are small islands. Oceanic islands are islands; the vast majority are volcanic in origin, such as Saint Helena in the South Atlantic Ocean. The few oceanic islands that are not volcanic are tectonic in origin and arise where plate movements have lifted up the ocean floor above the surface.
Examples are Saint Paul Rocks in the Atlantic Ocean and Macquarie Island in the Pacific. One type of volcanic oceanic island is found in a volcanic island arc; these islands arise from volcanoes. Examples are the Aleutian Islands, the Mariana Islands, most of Tonga in the Pacific Ocean; the only examples in the Atlantic Ocean are some of the Lesser Antilles and the South Sandwich Islands. Another type of volcanic oceanic island occurs. There are two examples: Iceland, the world's second largest volcanic island, Jan Mayen. Both are in the Atlantic. A third type of volcanic oceanic island is formed over volcanic hotspots. A hotspot is more or less stationary relative to the moving tectonic plate above it, so a chain of islands results as the plate drifts. Over long periods of time, this type of island is "drowned" by isostatic adjustment and eroded, becoming a seamount. Plate movement across a hot-spot produces a line of islands oriented in the direction of the plate movement. An example is the Hawaiian Islands, from Hawaii to Kure, which continue beneath the sea surface in a more northerly direction as the Emperor Seamounts.
Another chain with similar orientation is the Tuamotu Archipelago. The southernmost chain is the Austral Islands, with its northerly trending part the atolls in the nation of Tuvalu. Tristan da Cunha is an example of a hotspot volcano in the Atlantic Ocean. Another hotspot in the Atlantic is the island of Surtsey, formed in 1963. An atoll is an island formed from a coral reef that has grown on an eroded and submerged volcanic island; the reef forms a new island. Atolls are ring-shaped with a central lagoon. Examples are the Line Islands
Frederick William Beechey
Frederick William Beechey was an English naval officer and geographer. He was the son of two painters, Sir William Beechey RA. Born in London on 17 February 1796, he entered the Royal Navy at the age of 10, he was promoted to midshipman the following year and saw active service during the wars with France and America. In early 1818, now a lieutenant, Beechey sailed on HMS Trent under Lieutenant John Franklin in David Buchan's Arctic expedition, of which at a period he published a narrative. In the following year he accompanied Lieutenant W. E. Parry in HMS Hecla, sailing as far north as Melville Island. In 1821, as an officer on HMS Adventure, he took part in the survey of the Mediterranean coast of Africa under the direction of Captain William Henry Smyth, he and his brother, Henry William Beechey, made an overland survey of this coast and published a full account of their work in 1828 under the title of Proceedings of the Expedition to Explore the Northern Coast of Africa from Tripoly Eastward in 1821-1822.
In 1825, Beechey was appointed to command HMS Blossom. His task was to explore the Bering Strait in concert with Franklin and Parry operating from the east. In the summer of 1826, he passed the strait and a barge from his ship reached 71°23'31" N. and 156°21'30" W. near Point Barrow which he named, a point only 146 miles west of that reached by Franklin's expedition from the Mackenzie River. The whole voyage lasted more than three years and in the course of it Beechey discovered several islands in the Pacific, an excellent harbour near Cape Prince of Wales. In 1826, he visited a Catholic mission in California, he wrote, "...with whips and goads or sharp, pointed sticks to preserve silence and maintain order, what seemed more difficult than either, to keep the congregation in their kneeling posture. The goads would inflict a sharp puncture without making any noise; the end of the church was occupied by a guard of soldiers under arms with fixed bayonets." In July 1826, he named the three islands in the Bering Strait.
Two were the Diomede Islands that Vitus Bering had named in 1728: "Ratmanoff Island" and "Krusenstern Island". Beechey called the uninhabited third islet "Fairway Rock", still its contemporary name. One of his crew, Petty Officer John Bechervaise, gave a detailed account of the voyage in his Thirty-six Years of a Seafaring Life by an Old Quartermaster, published in 1839. In 1831, there appeared Beechey's Narrative of a Voyage to the Pacific and Bering's Strait to Co-operate with the Polar Expeditions, 1825-1828. In 1835, the following year Captain Beechey was employed on the coast survey of South America, from 1837 to 1847 carried on similar work along the Irish coasts, in the North Sea and English Channel, he carried out detailed tidal surveys during this period, which were published, with charts, in two Royal Society papers in 1848 and 1851. This was the first published work of its kind since Edmond Halley's tidal chart appeared in about 1702, he was appointed in 1850 to preside over the Marine Department of the Board of Trade.
In 1854, he was made rear-admiral, in the following year was elected president of the Royal Geographical Society. Beechey Island, where Sir John Franklin wintered, was named by him after his father, his daughter was the painter Frances Anne Hopkins who lived in Canada for twelve years and painted many scenes of canoe travel. His parents and three of his brothers were painters: the admiral and painter Richard Brydges Beechey, the portraitist Henry William Beechey, the portraitist George Duncan Beechey. European and American voyages of scientific exploration —. Proceedings Of The Expedition To Explore The Northern Coast Of Africa, From Tripoly Eastward. London: John Murray. Retrieved 15 August 2009. —. Narrative Of A Voyage To The Pacific And Beering's Strait, To Co-Operate With The Polar Expeditions Performed In His Majesty's Ship Blossom, Under The Command Of Captain F. W. Beechey, R. N. In The Years 1825, 26, 27, 28. Philadelphia: Carey & Lea. Retrieved 15 August 2009. —. A Voyage Of Discovery Towards The North Pole, Performed In His Majesty's Ships Dorothea And Trent, Under The Command Of Captain David Buchan, R. N. 1818.
London: Richard Bentley. Retrieved 15 August 2009. —. "Report of Observations Made Upon the Tides in the Irish Sea, Upon the Great Similarity of Tidal Phenomena of the Irish and English Channels, the Importance of Extending the Experiments Round the Land's End and up the English Channel. Embodied in a Letter to the Hydrographer". Philosophical Transactions of the Royal Society of London. 138: 105–116. Doi:10.1098/rstl.1848.0006. JSTOR 108287. —. "Report of Further Observations Made upon the Tidal Streams of the English Channel and German Ocean, under the Authority of the Admiralty, in 1849 and 1850". Abstracts of the Papers Communicated to the Royal Society of London. 6: 68–70. Doi:10.1098/rspl.1850.0024. —. "Report of Further Observations upon the Tidal Streams of the North Sea and English Channel, with Remarks upon the Laws by Which Those Streams Appear to be Governed". Philosophical Transactions of the Royal Society of London. 141: 703–718. Doi:10.1098/rstl.1851.0034. JSTOR 108420. —. "The Drawings and Watercolours".
Arctic. 33: 1–117. Doi:10.14430/arctic2551. JSTOR 40509279; this article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed.. "Beechey, Frederick William". Encyclopædia Britannica. 3. Cambridge University
A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission or from a combination of fission and fusion reactions. Both bomb types release large quantities of energy from small amounts of matter; the first test of a fission bomb released an amount of energy equal to 20,000 tons of TNT. The first thermonuclear bomb test released energy equal to 10 million tons of TNT. A thermonuclear weapon weighing little more than 2,400 pounds can release energy equal to more than 1.2 million tons of TNT. A nuclear device no larger than traditional bombs can devastate an entire city by blast and radiation. Since they are weapons of mass destruction, the proliferation of nuclear weapons is a focus of international relations policy. Nuclear weapons have been used twice in war, both times by the United States against Japan near the end of World War II. On August 6, 1945, the U. S. Army Air Forces detonated a uranium gun-type fission bomb nicknamed "Little Boy" over the Japanese city of Hiroshima.
S. Army Air Forces detonated a plutonium implosion-type fission bomb nicknamed "Fat Man" over the Japanese city of Nagasaki; these bombings caused injuries that resulted in the deaths of 200,000 civilians and military personnel. The ethics of these bombings and their role in Japan's surrender are subjects of debate. Since the atomic bombings of Hiroshima and Nagasaki, nuclear weapons have been detonated over two thousand times for testing and demonstration. Only a few nations are suspected of seeking them; the only countries known to have detonated nuclear weapons—and acknowledge possessing them—are the United States, the Soviet Union, the United Kingdom, China, India and North Korea. Israel is believed to possess nuclear weapons, though, in a policy of deliberate ambiguity, it does not acknowledge having them. Germany, Turkey and the Netherlands are nuclear weapons sharing states. South Africa is the only country to have independently developed and renounced and dismantled its nuclear weapons.
The Treaty on the Non-Proliferation of Nuclear Weapons aims to reduce the spread of nuclear weapons, but its effectiveness has been questioned, political tensions remained high in the 1970s and 1980s. Modernisation of weapons continues to this day. There are two basic types of nuclear weapons: those that derive the majority of their energy from nuclear fission reactions alone, those that use fission reactions to begin nuclear fusion reactions that produce a large amount of the total energy output. All existing nuclear weapons derive some of their explosive energy from nuclear fission reactions. Weapons whose explosive output is from fission reactions are referred to as atomic bombs or atom bombs; this has long been noted as something of a misnomer, as their energy comes from the nucleus of the atom, just as it does with fusion weapons. In fission weapons, a mass of fissile material is forced into supercriticality—allowing an exponential growth of nuclear chain reactions—either by shooting one piece of sub-critical material into another or by compression of a sub-critical sphere or cylinder of fissile material using chemically-fueled explosive lenses.
The latter approach, the "implosion" method, is more sophisticated than the former. A major challenge in all nuclear weapon designs is to ensure that a significant fraction of the fuel is consumed before the weapon destroys itself; the amount of energy released by fission bombs can range from the equivalent of just under a ton to upwards of 500,000 tons of TNT. All fission reactions generate the remains of the split atomic nuclei. Many fission products are either radioactive or moderately radioactive, as such, they are a serious form of radioactive contamination. Fission products are the principal radioactive component of nuclear fallout. Another source of radioactivity is the burst of free neutrons produced by the weapon; when they collide with other nuclei in surrounding material, the neutrons transmute those nuclei into other isotopes, altering their stability and making them radioactive. The most used fissile materials for nuclear weapons applications have been uranium-235 and plutonium-239.
Less used has been uranium-233. Neptunium-237 and some isotopes of americium may be usable for nuclear explosives as well, but it is not clear that this has been implemented, their plausible use in nuclear weapons is a matter of dispute; the other basic type of nuclear weapon produces a large proportion of its energy in nuclear fusion reactions. Such fusion weapons are referred to as thermonuclear weapons or more colloquially as hydrogen bombs, as they rely on fusion reactions between isotopes of hydrogen. All such weapons derive a significant portion of their energy from fission reactions used to "trigger" fusion reactions, fusion reactions can themselves trigger additional fission reactions. Only six countries—United States, United Kingdom, China and India—have conducted thermonuclear weapon tests. North Korea claims to have tested a fusion weapon as of January 2016. Thermonuclear weapons a