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Underground nuclear testing is the test detonation of nuclear weapons that is performed underground. When the device being tested is buried at sufficient depth, the explosion may be contained, with no release of radioactive materials to the atmosphere. The extreme heat and pressure of an underground nuclear explosion causes changes in 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 provided information that eventually led to the signing 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 Test Ban Treaty in 1996, most nuclear tests were performed underground, in order to prevent nuclear fallout from entering into the atmosphere. ==Background== Although public concern about fallout from nuclear testing grew in the early 1950s,〔(【引用サイトリンク】title=History of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) )〕 fallout was discovered after the Trinity test in 1945.〔 Photographic film manufacturers would later report 'fogged' films; this was traced to packaging materials sourced from Indiana crops, contaminated by the ''Trinity'' and later tests at the Nevada Test Site, over 1,000 miles away.〔 Intense fallout from the 1953 ''Simon'' test was documented as far as Albany, New York.〔 The fallout from the March 1954 ''Bravo'' test in the Pacific would have "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 was "insufficient" appreciation of the dangers of fallout.〔 The test became an international incident. In a 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 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 the health and environmental impact."〔(【引用サイトリンク】publisher=Public Broadcasting Service )〕 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.〔(【引用サイトリンク】publisher=US Department of State )〕 Talks between the United States, the United Kingdom, Canada, France, and the Soviet Union began in May 1955 on 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.〔(【引用サイトリンク】url=http://www.jfklibrary.org/Historical+Resources/JFK+in+History/Nuclear+Test+Ban+Treaty.htm )〕 Agreement was facilitated by the decision to allow underground testing, eliminating the need for on-site inspections that concerned 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."〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Underground nuclear weapons testing」の詳細全文を読む スポンサード リンク
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