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83-622: Cannikin was an underground nuclear weapons test performed on November 6, 1971, on Amchitka island, Alaska , by the United States Atomic Energy Commission . The experiment, part of the Operation Grommet nuclear test series, tested the unique W71 warhead design for the LIM-49 Spartan anti-ballistic missile. With an explosive yield of almost 5 megatons of TNT (21 PJ), the test

166-402: A melt cavity . The shock-induced motion and high internal pressure cause this cavity to expand outwards, which continues over several tenths of a second until the pressure has fallen sufficiently, to a level roughly comparable with the weight of the rock above, and can no longer grow. Although not observed in every explosion, four distinct zones (including the melt cavity) have been described in

249-496: A nose . In rowing races such as the Oxford and Cambridge Boat Race , the margin of victory and of defeat is expressed in fractions and multiples of boat lengths . The length of a rowing eight is about 62 feet (19 m). A shorter distance is the canvas , which is the length of the covered part of the boat between the bow and the bow oarsman. The Racing Rules of Sailing also makes heavy use of boat lengths. A football field

332-426: A Hammer unit is usually defined as a sixteenth of a foot (16 Hammer units = 1 foot). This means that 1 Hammer unit is equal to exactly 19.05 millimetres or 0.75 inches (3/4"). Button sizes are typically measured in ligne , which can be abbreviated as L. The measurement refers to the button diameter, or the largest diameter of irregular button shapes. There are 40 ligne in 1 inch. One rack unit (U)

415-612: A Wave Committee , founded that year in Vancouver , attempted to halt further nuclear testing on the Aleutian Islands chain. With the intention of sailing to Amchitka to protest the 1971 test, the committee chartered a ship it renamed Greenpeace . During the voyage to Amchitka, the test was delayed a month. The ship was turned back by the U.S. Coast Guard, although a letter given to the Greenpeace crew showed support for

498-491: A cavity with radius of 110 feet (34 m). Other surface features may include disturbed ground, pressure ridges , faults , water movement (including changes to the water table level), rockfalls, and ground slump. Most of the gas in the cavity is composed of steam; its volume decreases dramatically as the temperature falls and the steam condenses. There are however other gases, mostly carbon dioxide and hydrogen , which do not condense and remain gaseous. The carbon dioxide

581-561: A certain extent. A 150-by-135-metre (164 by 148 yd) football field has an area of approximately 15,900 m (1.59 ha; 3.9 acres), twice the area of a Canadian football field and three times that of an American football field. A morgen ("morning" in Dutch and German) was approximately the amount of land tillable by one man behind an ox in the morning hours of a day. This was an official unit of measurement in South Africa until

664-450: A height of 12,000 ft (3,700 m) and subsequent radioactive fallout drifted in an easterly direction, travelling as far as 140 mi (225 km) from ground zero. On 26 July 1957, Plumbbob Pascal-A was detonated at the bottom of a 486 ft (148 m) shaft. According to one description, it "ushered in the era of underground testing with a magnificent pyrotechnic roman candle !" As compared with an above-ground test,

747-467: A news article about an earthquake in Wales, stating that an area the size of Wales was affected. The Radio 4 programme More or Less introduced the idea of "kilowales" – an area 1,000 times the size of Wales. The Register introduced the nanowales (20.78 m ). The measurement has been adopted by rainforest conservation charity Size of Wales , aiming to conserve an area of rainforest equating to

830-447: A number of small tectonic events did occur in the following weeks, (some registering as high as 4.0 on the richter scale) thought to be due to the interaction of the explosion with local tectonic stresses. 51°28′12″N 179°06′11″E  /  51.47000°N 179.10306°E  / 51.47000; 179.10306 Underground nuclear testing The extreme heat and pressure of an underground nuclear explosion cause changes in

913-743: A series of aftershocks , thought to be a result of cavity collapse and chimney formation. In a few cases, seismic energy released by fault movements has exceeded that of the explosion itself. Signed in Moscow on August 5, 1963, by representatives of the United States, the Soviet Union, and the United Kingdom, the Limited Test Ban Treaty agreed to ban nuclear testing in the atmosphere, in space, and underwater. Due to

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996-451: A space its size; in 2018, it was estimated that approximately 2.6 billion people could fit on the Isle of Wight, at a population density of six people per square metre. In Hong Kong, the 19-hectare Victoria Park is used to define smaller areas. In Denmark , the outlying island of Bornholm (588 km or 227 sq mi) is often used to describe the size of an area. In Germany,

1079-603: A unit of length defined by the Eurocard printed circuit board standard used to measure the horizontal width of rack mounted electronic equipment, similar to the rack unit (U) used to measure vertical heights of rack mounted equipment. One HP is 0.2 inches (1/5") or 5.08 millimetres wide. Valve's Source game engine uses the Hammer unit as its base unit of length. This unit refers to Source's official map creation software, Hammer. The exact definition varies from game to game, but

1162-438: Is 1.75 inches (44.45 mm) and is used to measure rack-mountable audiovisual, computing and industrial equipment. Rack units are typically denoted without a space between the number of units and the 'U'. Thus, a 4U  server enclosure (case) is seven inches (177.8 mm) high, or more practically, built to occupy a vertical space seven inches high, with sufficient clearance to allow movement of adjacent hardware. The hand

1245-515: Is 105 m × 68 m (115 yd × 74 yd) for major competitions such as the FIFA World Cup , UEFA European Championship and UEFA Champions League . A Canadian football field is 65 yd (59 m) wide and 150 yd (140 m) long, including two 20 yd (18 m) long end zones. In most US cities, a city block is between 1 ⁄ 16 and 1 ⁄ 8  mi (100 and 200 m). In Manhattan ,

1328-424: Is 65 yards (59 m) wide and 110 yards (100 m) long with end zones adding a combined 40 yards (37 m) to the length, making it 87,750 square feet (8,152 m ) or 0.8215 ha (2.030 acres). An Australian rules football field may be approximately 150 metres (160 yd) (or more) long goal to goal and 135 metres (148 yd) (or more) wide, although the field's elliptical nature reduces its area to

1411-444: Is a unit of measurement that does not form part of a coherent system of measurement , especially because its exact quantity may not be well known or because it may be an inconvenient multiple or fraction of a base unit. Many of the unusual units of measurements listed here are colloquial measurements, units devised to compare a measurement to common and familiar objects. In genetics, a centimorgan (abbreviated cM) or map unit (m.u.)

1494-497: Is a common reference. The US Central Intelligence Agency uses Washington, D.C. (61.4 sq mi or 159 km ) as a comparison for city-sized objects. In the Netherlands, its smallest province, Utrecht (1,386 km or 535 sq mi), is often used as a comparison for regions in general. The country of Belgium (30,528 km or 11,787 sq mi) has also often been used when comparing areas, to

1577-502: Is a non- SI unit of length equal to exactly 4 inches (101.6 mm). It is normally used to measure the height of horses in some English-speaking countries, including Australia, Canada, Ireland, the United Kingdom, and the United States. It is customary when measuring in hands to use a point to indicate inches (quarter-hands) and not tenths of a hand . For example, 15.1 hands normally means 15 hands, 1 inch (5 ft 1 in), rather than 15 + 1 ⁄ 10 hands. The light-nanosecond

1660-399: Is a unit for measuring genetic linkage. It is defined as the distance between chromosome positions (also termed loci or markers) for which the expected average number of intervening chromosomal crossovers in a single generation is 0.01. It is often used to infer distance along a chromosome. One centimorgan corresponds to about 1 million base pairs in humans on average. Horizontal pitch (HP) is

1743-477: Is a unit of vertical distance often—but not always—corresponding to the height of an ordinary line of text. One barn is 10  square metres, about the cross-sectional area of a uranium nucleus. The name probably derives from early neutron-deflection experiments, when the uranium nucleus was described, and the phrases "big as a barn" and "hit a barn door" were used. Barn are typically used for cross sections in nuclear and particle physics. Additional units include

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1826-498: Is an approximation of the imperial ounce, US dry ounce, or US fluid ounce. These three customary units vary. However, the metric ounce is usually taken as 25 or 30 ml (0.88 or 1.06 imp fl oz; 0.85 or 1.01 US fl oz) when volume is being measured, or in grams when mass is being measured. The US Food and Drug Administration (FDA) defines the "food labeling ounce" as 30 ml (1.1 imp fl oz; 1.0 US fl oz), slightly larger than

1909-406: Is around one third of a metre, with the exact definition depending on jurisdiction. Horses are used to measure distances in horse racing – a horse length (shortened to merely a length when the context makes it obvious) equals roughly 8 feet or 2.4 metres. Shorter distances are measured in fractions of a horse length ; also common are measurements of a full or fraction of a head , a neck , or

1992-504: Is defined as exactly 29.9792458 cm. It was popularized in information technology as a unit of distance by Grace Hopper as the distance which a photon could travel in one billionth of a second (roughly 30 cm or one foot): "The speed of light is one foot per nanosecond." A metric foot, defined as 300 millimetres (approximately 11.811 inches), has been used occasionally in the UK but has never been an official unit. A Chinese foot

2075-469: Is often given in the number of blocks east–west plus the number north–south (known to mathematicians as the Manhattan Metric ). The globally-average radius of Earth , generally given as 6,371 kilometres (3,959 miles), is often employed as a unit of measure to intuitively compare objects of planetary size. Lunar distance (LD), the distance from the centre of Earth to the centre of

2158-577: Is often used as a comparative measurement of length when talking about distances that may be hard to comprehend when stated in terms of standard units. An American football field is usually understood to be 100 yards (91 m) long, though it is technically 120 yards (110 m) when including the two 10 yd (9.1 m) long end zones. The field is 160 ft (53 yd; 49 m) wide. An association football pitch may vary within limits of 90–120 m (98–131 yd) in length and 45–90 m (49–98 yd) in width. The recommended field size

2241-399: Is originally the length from someone's elbow to the tip of their middle finger; it usually translates to approximately half a metre ±10%, with an ancient Roman cubit being as long as 120 cm. One cubit was equal to 6–7 palms , one palm being the width of a hand not including the thumb. In groff / troff and specifically in the included traditional manuscript macro set ms , the vee (v)

2324-594: Is prevalent in the construction industry in India . The same area is called a square in the construction industry in North America, and was historically used in Australia by real estate agents. A roof 's area may be calculated in square feet, then converted to squares. In Ireland, before the 19th century, a "cow's grass" was a measurement used by farmers to indicate the size of their fields. A cow's grass

2407-410: Is produced by thermal decomposition of carbonates , hydrogen is created by reaction of iron and other metals from the nuclear device and surrounding equipment. The amount of carbonates and water in the soil and the available iron have to be considered in evaluating the test site containment; water-saturated clay soils may cause structural collapse and venting. Hard basement rock may reflect shock waves of

2490-469: Is the Baneberry test. Slow, low-pressure uncontrolled releases of radioactivity are known as seeps ; these have little to no energy, are not visible and have to be detected by instruments. Late-time seeps are releases of noncondensable gases days or weeks after the blast, by diffusion through pores and crack, probably assisted by a decrease of atmospheric pressure (so called atmospheric pumping ). When

2573-499: The Nevada Test Site , 95 percent of tests conducted at a scaled depth of burial (SDOB) of less than 150 caused surface collapse, compared with about half of tests conducted at a SDOB of less than 180. The radius r (in feet) of the cavity is proportional to the cube root of the yield y (in kilotons), r = 55 * y 3 {\displaystyle {\sqrt[{3}]{y}}} ; an 8 kiloton explosion will create

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2656-574: The epicentre , and distinguish between the seismic signatures of an underground nuclear explosion and an earthquake. Additionally, eighty radionuclide stations detect radioactive particles vented by underground explosions. Certain radionuclides constitute clear evidence of nuclear tests; the presence of noble gases can indicate whether an underground explosion has taken place. Finally, eleven hydroacoustic stations and sixty infrasound stations monitor underwater and atmospheric tests. Hiroshima bomb (unit) An unusual unit of measurement

2739-678: The 1953 Simon test was documented as far as Albany, New York. The fallout from the March 1954 Bravo test in the Pacific Ocean had "scientific, political and social implications that have continued for more than 40 years". The multi- megaton test caused fallout to occur on the islands of the Rongerik and Rongelap atolls, and a Japanese fishing boat known as the Daigo Fukuryū Maru (Lucky Dragon). Prior to this test, there

2822-877: The 1960s, but the atmospheric testing component was abandoned following the establishment of the Partial Nuclear Test Ban Treaty . Preparation for the test took place over five years and involved hundreds of staff from the Lawrence Radiation Laboratory, later the Lawrence Livermore National Laboratory . Drilling for the shaft for the Milrow test began in March 1967, with drilling for the Cannikin test commencing in August 1967. To perform

2905-604: The 1969 calibration test and Cannikin itself attracted protest. Because of the 1964 Alaska earthquake , the plans raised concerns that tests might trigger earthquakes and cause a tsunami . A 1969 demonstration of 7,000 people blocked a major U.S.–Canada border crossing in British Columbia, carrying signs reading "Don't Make A Wave. It's Your Fault If Our Fault Goes". Further demonstrations occurred at Canada–US border crossings in Ontario and Quebec. The Canadian Don't Make

2988-588: The 1970s, and was defined in November 2007 by the South African Law Society as having a conversion factor of 1 morgen = 0.856 532  hectares . This unit of measure was also used in the Dutch colonial province of New Netherland (later New York and parts of New England ). The area of a familiar country, state or city is often used as a unit of measure, especially in journalism . Equal to 20,779 km (8,023 sq mi),

3071-411: The 29.6 ml (1.04 imp fl oz; 1.00 US fl oz) fluid ounce . Several Dutch units of measurement have been replaced with informal metric equivalents, including the ons or ounce. It originally meant 1 ⁄ 16 of a pound, or a little over 30 g (1.1 oz) depending on which definition of the pound was used, but was redefined as 100 g (3.5 oz) when

3154-458: The Moon, is a unit of measure in astronomy. The lunar distance is approximately 384,400 km (238,900 mi), or 1.28 light-seconds ; this is roughly 30 times Earth's diameter . A little less than 400 lunar distances make up an astronomical unit . The siriometer is an obsolete astronomical measure equal to one million astronomical units , i.e., one million times the average distance between

3237-584: The Soviet government's concern about the need for on-site inspections, underground tests were excluded from the ban. 108 countries eventually signed the treaty, with the significant exception of China. In 1974, the United States and the Soviet Union signed the Threshold Test Ban Treaty (TTBT) which banned underground tests with yields greater than 150 kilotons. By the 1990s, technologies to monitor and detect underground tests had matured to

3320-562: The Soviets. Underground testing was allowed, provided that it does not cause "radioactive debris to be present outside the territorial limits of the State under whose jurisdiction or control such explosion is conducted". Following analysis of underwater detonations that were part of Operation Crossroads in 1946, inquiries were made regarding the possible military value of an underground explosion. The US Joint Chiefs of Staff thus obtained

3403-730: The Sun and Earth. This distance is equal to about 15.8  light-years , 149.6  Pm , or 4.8  parsecs , and is about twice the distance from Earth to the star Sirius . The cubit is, among others, a unit used in the Bible for measuring the size of Noah's Ark and of the Ark of the Covenant . Cubits of various lengths were used in Antiquity by various peoples, not only the Hebrews. One cubit

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3486-546: The United States), and instead wanted an international detection system. The resulting International Monitoring System (IMS) consists of a network of 321 monitoring stations, and 16 radionuclide laboratories. Fifty "primary" seismic stations send data continuously to the International Data Center, along with 120 "auxiliary" stations which send data on request. The resulting data is used to locate

3569-581: The agreement of the United States Atomic Energy Commission (AEC) to perform experiments on both surface and sub-surface detonations. The Alaskan island of Amchitka was initially selected for these tests in 1950, but the site was later deemed unsuitable and the tests were moved to the Nevada Test Site. The first underground nuclear test was conducted on 29 November 1951. This was the 1.2  kiloton Buster-Jangle Uncle , which detonated 17 ft (5.2 m) beneath ground level. The test

3652-498: The area of Wales. On 1 March 2013, the charity announced that they had succeeded in conserving an area of rainforest the size of Wales and will continue to operate to sustain and increase the protected area. In the United States, the area of the smallest state, Rhode Island (1,545 sq mi or 4,000 km ); the largest of the contiguous 48 states, Texas (268,601 sq mi or 695,670 km ); and less commonly Alaska (656,425 sq mi or 1,700,130 km ),

3735-509: The atmosphere (the resulting crater is usually conical in profile, circular, and may range between tens to hundreds of yards in diameter and depth ). One figure used in determining how deeply the device should be buried is the scaled depth of burial , or -burst (SDOB) This figure is calculated as the burial depth divided by the cube root of the yield. It is estimated that, in order to ensure containment, this figure should be greater than 300 ft (100 m) per kiloton . The energy of

3818-504: The atmosphere. Public concern about fallout from nuclear testing grew in the early 1950s. Fallout was discovered after the Trinity test, the first ever atomic bomb test, in 1945. Photographic film manufacturers later reported 'fogged' films ; this was traced to packaging materials sourced from Indiana crops, contaminated by Trinity and later tests at the Nevada Test Site , over 1,000 miles (1,600 km) away. Intense fallout from

3901-406: The country of Wales is used in phrases such as "an area the size of Wales" or "twice the area of Wales". England is 6.275 times the size of Wales, and Scotland is roughly four times the size of Wales. Ireland is four times as large as Wales, and France is about twenty-five times larger. The British comedy show The Eleven O'Clock Show parodied the use of this measurement, by introducing

3984-446: The depth and yield of the explosion , as well as the nature of the surrounding rock. If the test is conducted at sufficient depth, the test is said to be contained , with no venting of gases or other contaminants to the environment. In contrast, if the device is buried at insufficient depth ("underburied"), then rock may be expelled by the explosion, forming a subsidence crater surrounded by ejecta , and releasing high-pressure gases to

4067-477: The explosion, also possibly causing structural weakening and venting. The noncondensible gases may stay absorbed in the pores in the soil. Large amount of such gases can however maintain enough pressure to drive the fission products to the ground. Escape of radioactivity from the cavity is known as containment failure . Massive, prompt, uncontrolled releases of fission products, driven by the pressure of steam or gas, are known as venting ; an example of such failure

4150-477: The health and environmental impact." The Prime Minister of India "voiced the heightened international concern" when he called for the elimination of all nuclear testing worldwide. Knowledge about fallout and its effects grew, and with it concern about the global environment and long-term genetic damage . Talks between the United States, the United Kingdom, Canada, France, and the Soviet Union began in May 1955 on

4233-403: The injunction by 4 votes to 3. The test was carried out but, although it triggered small earthquakes, did not cause a tsunami as feared. Cannikin was detonated on November 6, 1971 , as the thirteenth test of the Operation Grommet (1971–1972) underground nuclear test series. The announced yield was 5 megatons (21 PJ) – the largest underground nuclear test in U.S. history. (Estimates for

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4316-420: The largest of all 50 states, are used in a similar fashion. For example, Antarctica 's Larsen B ice shelf was approximately the size of Rhode Island until it broke up in 2002. Other areas may be described like this, too, like in the 1979 movie The China Syndrome when radiation is expected to contaminate "an area the size of Pennsylvania ". The island of Manhattan (22.83 sq mi or 59.1 km )

4399-404: The measurement "block" usually refers to a north–south block, which is 1 ⁄ 20  mi (80 m). Sometimes people living in places (like Manhattan) with a regularly spaced street grid will speak of long blocks and short blocks . Within a typical large North American city, it is often only possible to travel along east–west and north–south streets, so travel distance between two points

4482-546: The media. There are all kinds of letters and protests that come from, not surprisingly, Japanese fishermen, the fishermen's wives; there are student groups, all different types of people; that protest against the Americans' use of the Pacific for nuclear testing. They're very concerned about, first of all, why the United States even has the right to be carrying out those kinds of tests in the Pacific. They're also concerned about

4565-489: The microbarn (or "outhouse") and the yoctobarn (or "shed"). A Kuang is a traditional Chinese unit of area used in sampling , equal to 0.11 square metres or one square Chinese foot . One brass is exactly 100 square feet (9.29 m ) area (used in measurement of work done or to be done, such as plastering, painting, etc.). The same word is used, however, for 100 cubic feet (2.83 m ) of estimated or supplied loose material, such as sand, gravel, rubble, etc. This unit

4648-500: The milk of grazing cows; cow milk is therefore a convenient, sensitive fallout indicator. Soft tissues of animals can be analyzed for gamma emitters , bones and liver for strontium and plutonium , and blood, urine and soft tissues are analyzed for tritium. Although there were early concerns about earthquakes arising as a result of underground tests, there is no evidence that this has occurred. However, fault movements and ground fractures have been reported, and explosions often precede

4731-422: The nuclear explosion is released in one microsecond . In the following few microseconds, the test hardware and surrounding rock are vaporised, with temperatures of several million degrees and pressures of several million atmospheres . Within milliseconds , a bubble of high-pressure gas and steam is formed. The heat and expanding shock wave cause the surrounding rock to vaporise, or be melted further away, creating

4814-400: The pitch is not used for international competition), which generally results in the association football pitch generally only being used for order of magnitude comparisons. An American football field , including both end zones, is 360 by 160 ft (120.0 by 53.3 yd; 109.7 by 48.8 m), or 57,600 square feet (5,350 m ) (0.535 hectares or 1.32 acres). A Canadian football field

4897-537: The point that tests of one kiloton or over could be detected with high probability, and in 1996 negotiations began under the auspices of the United Nations to develop a comprehensive test ban. The resulting Comprehensive Nuclear-Test-Ban Treaty was signed in 1996 by the United States, Russia, United Kingdom, France, and China. However, following the United States Senate decision not to ratify

4980-423: The point where it has been regarded as a meme and where there is a website dedicated to notable areas which have been compared to that of Belgium. The Isle of Wight (380 km or 147 sq mi), an island off the south coast of mainland England , is commonly used to define smaller areas. It has sometimes been used in attempts to examine whether a certain amount of a given object or group would fit in

5063-613: The precise yield range from 4.4 to 5.2 megatons or 18 to 22 PJ). The ground lifted 20 feet (6 m), caused by an explosive force almost 400 times the power of the Hiroshima bomb . Subsidence and faulting at the site created a new lake, several hundred meters wide. The explosion caused a seismic shock of 7.0 on the Richter scale , causing rockfalls and turf slides of a total of 35,000 square feet (3,300 m). Though earthquakes and tsunamis predicted by environmentalists did not occur,

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5146-422: The pressure in the cavity falls below the level needed to support the overburden, the rock above the void falls into the cavity. Depending on various factors, including the yield and characteristics of the burial, this collapse may extend to the surface. If it does, a subsidence crater is created. Such a crater is usually bowl-shaped, and ranges in size from around 100 feet to over half a mile in diameter. At

5229-560: The protest by some on the intervening Coast Guard ship. Under their own ship's name, the organization created for the protest continued to exist as the campaigning environmental organization Greenpeace . In July 1971, the anti-nuclear Committee for Nuclear Responsibility filed suit against the Atomic Energy Commission, asking the court to stop the test. The suit was unsuccessful, with the Supreme Court denying

5312-429: The radioactive debris released to the atmosphere was reduced by a factor of ten. Theoretical work began on possible containment schemes. Plumbbob Rainier was detonated at 899 ft (274 m) underground on 19 September 1957. The 1.7 kt explosion was the first to be entirely contained underground, producing no fallout. The test took place in a 1,600 to 2,000 ft (500 to 600 m) horizontal tunnel in

5395-565: The sampling of explosion gases. The radionuclide composition differs by the type of releases; large prompt venting releases significant fraction (up to 10%) of fission products, while late-time seeps contain only the most volatile gases. Soil absorbs the reactive chemical compounds, so the only nuclides filtered through soil into the atmosphere are the noble gases , primarily krypton-85 and xenon-133 . The released nuclides can undergo bio-accumulation . Radioactive isotopes like iodine-131 , strontium-90 and caesium-137 are concentrated in

5478-427: The shape of a hook. The hook "was designed so explosive force will seal off the non-curved portion of tunnel nearest the detonation before gases and fission fragments can be vented around the curve of the tunnel's hook". This test would become the prototype for larger, more powerful tests. Rainier was announced in advance, so that seismic stations could attempt to record a signal. Analysis of samples collected after

5561-456: The state of Saarland (2,569.69 km or 992.16 sq mi) is often used to define areas. In Brazil , it is common to compare relatively small areas to the state of Sergipe (21,910.4 km or 8,459.7 sq mi), the smallest in the country. Smaller areas are sometimes compared to the cities of São Paulo (1,521.11 km or 587.30 sq mi) or Rio de Janeiro (1,221 km or 471 sq mi). A metric ounce

5644-421: The strain and subsequent release then forms a seismic wave . A few seconds later the molten rock starts collecting on the bottom of the cavity and the cavity content begins cooling. The rebound after the shock wave causes compressive forces to build up around the cavity, called a stress containment cage , sealing the cracks. Several minutes to days later, once the heat dissipates enough, the steam condenses, and

5727-605: The subject of an international agreement to end nuclear tests. On August 5, 1963, representatives of the United States , the Soviet Union , and the United Kingdom signed the Limited Test Ban Treaty, forbidding testing of nuclear weapons in the atmosphere, in space, and underwater. Agreement was facilitated by the decision to allow underground testing, eliminating the need for on-site inspections that concerned

5810-402: The surrounding rock. The crushed zone , about two times the radius of the cavity, consists of rock that has lost all of its former integrity. The cracked zone , about three times the cavity radius, consists of rock with radial and concentric fissures. Finally, the zone of irreversible strain consists of rock deformed by the pressure. The following layer undergoes only an elastic deformation ;

5893-543: The surrounding rock. The rock closest to the location of the test is vaporised , forming a cavity. Farther away, there are zones of crushed, cracked, and irreversibly strained rock. Following the explosion, the rock above the cavity may collapse, forming a rubble chimney. If this chimney reaches the surface, a bowl-shaped subsidence crater may form. The first underground test took place in 1951. Further tests soon led scientists to conclude that even notwithstanding environmental and diplomatic considerations, underground testing

5976-551: The test enabled scientists to develop an understanding of underground explosions that "persists essentially unaltered today". The information would later provide a basis for subsequent decisions to agree to the Limited Test Ban Treaty. Cannikin , the last test at the facility on Amchitka, was detonated on 6 November 1971. At approximately five megatons , it was the largest underground test in US history. The effects of an underground nuclear test may vary according to factors including

6059-406: The test tunnel has to be accessed, controlled tunnel purging is performed; the gases are filtered, diluted by air and released to atmosphere when the winds will disperse them over sparsely populated areas. Small activity leaks resulting from operational aspects of tests are called operational releases ; they may occur e.g. during drilling into the explosion location during core sampling , or during

6142-403: The test, 400 tons of equipment was placed in a shaft 1,870 metres (6,150 ft) deep and 2.3 metres (90 in) wide. Test support equipment was designed to survive a ground upheaval of 4.6 metres (15 ft) at test time. The chairman of the Atomic Energy Commission, James R. Schlesinger , brought his wife and two daughters to Amchitka for the test to emphasize the safety of the test. Both

6225-526: The test. The Cannikin test was too large to be conducted safely at Nevada Test Site . Amchitka had been considered in the 1950s as a potential nuclear test site, but had been deemed unsuitable at that time. In 1965, a single nuclear test, Long Shot , was carried out on the island for the purposes of seismic test detection development, under program Vela Uniform . The Amchitka site was again investigated as an atmospheric nuclear test site for intercontinental ballistic missile silo design under Project Rufus in

6308-425: The treaty in 1999, it is still yet to be ratified by 8 of the required 44 'Annex 2' states and so has not entered into force as United Nations law. In the late 1940s, the United States began to develop the capability to detect atmospheric testing using air sampling; this system was able to detect the first Soviet test in 1949. Over the next decade, this system was improved, and a network of seismic monitoring stations

6391-529: Was Teapot Ess , on 23 March 1955. The one-kiloton explosion was an operational test of an ' Atomic Demolition Munition ' (ADM). It was detonated 67 ft (20 m) underground, in a shaft lined with corrugated steel, which was then back-filled with sandbags and dirt. Because the ADM was buried underground, the explosion blew tons of earth upwards, creating a crater 300 ft (90 m) wide and 128 ft (39 m) deep. The resulting mushroom cloud rose to

6474-461: Was "insufficient" appreciation of the dangers of fallout. The test became an international incident. In a Public Broadcasting Service (PBS) interview, the historian Martha Smith argued: "In Japan, it becomes a huge issue in terms of not just the government and its protest against the United States, but all different groups and all different peoples in Japan start to protest. It becomes a big issue in

6557-453: Was designed as a scaled-down investigation of the effects of a 23-kiloton ground-penetrating gun-type fission weapon that was then being considered for use as a cratering and bunker-buster weapon. The explosion resulted in a cloud that rose to 11,500 ft (3,500 m), and deposited fallout to the north and north-northeast. The resulting crater was 260 ft (79 m) wide and 53 ft (16 m) deep. The next underground test

6640-532: Was equal to the amount of land that could produce enough grass to support a cow. A football pitch , or field, can be used as a man-in-the-street unit of area. The standard FIFA football pitch for international matches is 105 m (344 ft) long by 68 m (223 ft) wide (7,140 m or 0.714 ha or 1.76 acres); FIFA allows for a variance of up to 5 m (16.4 ft) in length in either direction and 7 m (23.0 ft) more or 4 m (13.1 ft) less in width (and larger departures if

6723-505: Was established to detect underground tests. Development of the Threshold Test Ban Treaty in the mid-1970s led to an improved understanding of the relationship between test yield and resulting seismic magnitude. When negotiations began in the mid-1990s to develop a comprehensive test ban, the international community was reluctant to rely upon the detection capabilities of individual nuclear weapons states (especially

6806-642: Was of far greater scientific value than all other forms of testing. This understanding strongly influenced the governments of the first three nuclear powers to sign of the Limited Test Ban Treaty in 1963, which banned all nuclear tests except for those performed underground. From then until the signing of the Comprehensive Nuclear-Test-Ban Treaty in 1996, most nuclear tests were performed underground, which prevented additional nuclear fallout from entering into

6889-597: Was the largest underground explosion ever detonated by the United States. Prior to the main five-megaton test in 1971, a 1 Mt (4.2 PJ) test took place on the island on October 2, 1969, for calibration purposes, and to ensure the subsequent Cannikin test could be contained. This test, Milrow , was included in the Operation Mandrel nuclear test series. The Cannikin test faced considerable opposition on environmental grounds. The campaigning environmental organization Greenpeace grew out of efforts to oppose

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