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An explosion is a rapid expansion in
volume Volume is a measure of occupied three-dimensional space. It is often quantified numerically using SI derived units (such as the cubic metre and litre) or by various imperial or US customary units (such as the gallon, quart, cubic inch). Th ...
associated with an extreme outward release of
energy In physics, energy (from Ancient Greek: ἐνέργεια, ''enérgeia'', “activity”) is the quantitative property that is transferred to a body or to a physical system, recognizable in the performance of work and in the form of hea ...
, usually with the generation of high
temperatures Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have relied on ...
and release of high-pressure
gas Gas is one of the four fundamental states of matter (the others being solid, liquid, and plasma). A pure gas may be made up of individual atoms (e.g. a noble gas like neon), elemental molecules made from one type of atom (e.g. oxygen), or ...
es. Supersonic explosions created by
high explosive An explosive (or explosive material) is a reactive substance that contains a great amount of potential energy that can produce an explosion if released suddenly, usually accompanied by the production of light, heat, sound, and pressure. An ...
s are known as
detonation Detonation () is a type of combustion involving a supersonic exothermic front accelerating through a medium that eventually drives a shock front propagating directly in front of it. Detonations propagate supersonically through shock waves with s ...
s and travel through
shock wave In physics, a shock wave (also spelled shockwave), or shock, is a type of propagating disturbance that moves faster than the local speed of sound in the medium. Like an ordinary wave, a shock wave carries energy and can propagate through a me ...
s. Subsonic explosions are created by
low explosive An explosive (or explosive material) is a reactive substance that contains a great amount of potential energy that can produce an explosion if released suddenly, usually accompanied by the production of light, heat, sound, and pressure. An expl ...
s through a slower
combustion Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel (the reductant) and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke. Combus ...
process known as deflagration.


Causes

Explosions can occur in nature due to a large
influx Influx may refer to: * Flux (biology) of ions, molecules or other substances from the extracellular space to the intracellular space * ''Influx'', a 2014 science-fiction novel by Daniel Suarez Daniel is a masculine given name and a surname of ...
of energy. Most natural explosions arise from
volcanic A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plates a ...
or stellar processes of various sorts. Explosive volcanic eruptions occur when
magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma is found beneath the surface of the Earth, and evidence of magmatism has also been discovered on other terrestrial planets and some natural sa ...
rises from below, it has very dissolved gas in it. The reduction of
pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and e ...
as the magma rises and causes the gas to bubble out of solution, resulting in a rapid increase in volume. Explosions also occur as a result of impact events and in phenomena such as hydrothermal explosions (also due to volcanic processes). Explosions can also occur outside of Earth in the universe in events such as supernovae. Explosions frequently occur during
bushfires A wildfire, forest fire, bushfire, wildland fire or rural fire is an unplanned, uncontrolled and unpredictable fire in an area of combustible vegetation. Depending on the type of vegetation present, a wildfire may be more specifically identif ...
in
eucalyptus ''Eucalyptus'' () is a genus of over seven hundred species of flowering trees, shrubs or mallees in the myrtle family, Myrtaceae. Along with several other genera in the tribe Eucalypteae, including '' Corymbia'', they are commonly known as e ...
forests where the volatile oils in the tree tops suddenly combust.


Astronomical

Among the largest known explosions in the universe are supernovae, which occur after the end of life of some types of
stars A star is an astronomical object comprising a luminous spheroid of plasma held together by its gravity. The nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night, but their immense distances from Earth ma ...
. Solar flares are an example of a common, much less energetic explosion on the Sun, and presumably on most other stars as well. The energy source for solar flare activity comes from the tangling of magnetic field lines resulting from the rotation of the Sun's conductive plasma. Another type of large astronomical explosion occurs when a very large meteoroid or an asteroid impacts the surface of another object, such as a planet. For example, the
Tunguska event The Tunguska event (occasionally also called the Tunguska incident) was an approximately 12- megaton explosion that occurred near the Podkamennaya Tunguska River in Yeniseysk Governorate (now Krasnoyarsk Krai), Russia, on the morning of June 3 ...
of 1908 is believed to have resulted from a meteor air burst. Black hole mergers, likely involving binary black hole systems, are capable of radiating many solar masses of energy into the universe in a fraction of a second, in the form of a gravitational wave. This is capable of transmitting ordinary energy and destructive forces to nearby objects, but in the vastness of space, nearby objects are usually rare. The gravitational wave observed on 21 May 2019, known as GW190521, produced a merger signal of about 100 ms duration, during which time is it estimated to have radiated away 9 solar masses in the form of gravitational energy.


Chemical

The most common artificial explosives are chemical explosives, usually involving a rapid and violent
oxidation Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a ...
reaction that produces large amounts of hot gas. Gunpowder was the first explosive to be invented and put to use. Other notable early developments in chemical explosive technology were
Frederick Augustus Abel Sir Frederick Augustus Abel, 1st Baronet (17 July 18276 September 1902) was an English chemist who was recognised as the leading British authority on explosives. He is best known for the invention of cordite as a replacement for gunpowder in f ...
's development of nitrocellulose in 1865 and Alfred Nobel's invention of dynamite in 1866. Chemical explosions (both intentional and accidental) are often initiated by an electric spark or flame in the presence of oxygen. Accidental explosions may occur in fuel tanks, rocket engines, etc.


Electrical and magnetic

A high current electrical fault can create an 'electrical explosion' by forming high energy
electrical arc An electric arc, or arc discharge, is an electrical breakdown of a gas that produces a prolonged electrical discharge. The current through a normally nonconductive medium such as air produces a plasma; the plasma may produce visible light. ...
which rapidly vaporizes metal and insulation material. This arc flash hazard is a danger to people working on energized
switchgear In an electric power system, a switchgear is composed of electrical disconnect switches, fuses or circuit breakers used to control, protect and isolate electrical equipment. Switchgear is used both to de-energize equipment to allow work to be ...
. Excessive
magnetic pressure In physics, magnetic pressure is an energy density associated with a magnetic field. In SI units, the energy density P_B of a magnetic field with strength B can be expressed as :P_B = \frac where \mu_0 is the vacuum permeability. Any magnetic fie ...
within an ultra-strong
electromagnet An electromagnet is a type of magnet in which the magnetic field is produced by an electric current. Electromagnets usually consist of wire wound into a coil. A current through the wire creates a magnetic field which is concentrated in ...
can cause a ''magnetic explosion''.


Mechanical and vapor

Strictly a physical process, as opposed to chemical or nuclear, e.g., the bursting of a sealed or partially sealed container under internal pressure is often referred to as an explosion. Examples include an overheated boiler or a simple tin can of beans tossed into a fire. Boiling liquid expanding vapor explosions are one type of mechanical explosion that can occur when a vessel containing a pressurized liquid is ruptured, causing a rapid increase in volume as the liquid evaporates. Note that the contents of the container may cause a subsequent chemical explosion, the effects of which can be dramatically more serious, such as a propane tank in the midst of a fire. In such a case, to the effects of the mechanical explosion when the tank fails are added the effects from the explosion resulting from the released (initially liquid and then almost instantaneously gaseous) propane in the presence of an ignition source. For this reason, emergency workers often differentiate between the two events.


Nuclear

In addition to stellar
nuclear explosion A nuclear explosion is an explosion that occurs as a result of the rapid release of energy from a high-speed nuclear reaction. The driving reaction may be nuclear fission or nuclear fusion or a multi-stage cascading combination of the two, tho ...
s, a
nuclear weapon A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission (fission bomb) or a combination of fission and fusion reactions ( thermonuclear bomb), producing a nuclear explosion. Both bom ...
is a type of explosive weapon that derives its destructive force from nuclear fission or from a combination of fission and fusion. As a result, even a nuclear weapon with a small yield is significantly more powerful than the largest conventional explosives available, with a single weapon capable of completely destroying an entire city.


Properties


Force

Explosive force is released in a direction perpendicular to the surface of the explosive. If a grenade is in mid air during the explosion, the direction of the blast will be 360°. In contrast, in a
shaped charge A shaped charge is an explosive charge shaped to form an explosively formed penetrator (EFP) to focus the effect of the explosive's energy. Different types of shaped charges are used for various purposes such as cutting and forming metal, ini ...
the explosive forces are focused to produce a greater local explosion; shaped charges are often used by military to breach doors or walls.


Velocity

The speed of the reaction is what distinguishes an explosive reaction from an ordinary combustion reaction. Unless the reaction occurs very rapidly, the thermally expanding gases will be moderately dissipated in the medium, with no large differential in pressure and no explosion. As a wood fire burns in a fireplace, for example, there certainly is the evolution of heat and the formation of gases, but neither is liberated rapidly enough to build up a sudden substantial pressure differential and then cause an explosion. This can be likened to the difference between the energy discharge of a
battery Battery most often refers to: * Electric battery, a device that provides electrical power * Battery (crime), a crime involving unlawful physical contact Battery may also refer to: Energy source *Automotive battery, a device to provide power t ...
, which is slow, and that of a flash
capacitor A capacitor is a device that stores electrical energy in an electric field by virtue of accumulating electric charges on two close surfaces insulated from each other. It is a passive electronic component with two terminals. The effect of ...
like that in a
camera A camera is an optical instrument that can capture an image. Most cameras can capture 2D images, with some more advanced models being able to capture 3D images. At a basic level, most cameras consist of sealed boxes (the camera body), with a ...
flash, which releases its energy all at once.


Evolution of heat

The generation of heat in large quantities accompanies most explosive chemical reactions. The exceptions are called entropic explosives and include organic peroxides such as acetone peroxide. It is the rapid liberation of heat that causes the gaseous products of most explosive reactions to expand and generate high
pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and e ...
s. This rapid generation of high pressures of the released gas constitutes the explosion. The liberation of heat with insufficient rapidity will not cause an explosion. For example, although a unit mass of coal yields five times as much heat as a unit mass of nitroglycerin, the coal cannot be used as an explosive (except in the form of coal dust) because the rate at which it yields this heat is quite slow. In fact, a substance that burns less rapidly (''i.e.'' slow
combustion Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel (the reductant) and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke. Combus ...
) may actually evolve more total heat than an explosive that detonates rapidly (''i.e.'' fast
combustion Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel (the reductant) and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke. Combus ...
). In the former, slow combustion converts more of the internal energy (''i.e.''
chemical potential In thermodynamics, the chemical potential of a species is the energy that can be absorbed or released due to a change of the particle number of the given species, e.g. in a chemical reaction or phase transition. The chemical potential of a species ...
) of the burning substance into heat released to the surroundings, while in the latter, fast combustion (''i.e.''
detonation Detonation () is a type of combustion involving a supersonic exothermic front accelerating through a medium that eventually drives a shock front propagating directly in front of it. Detonations propagate supersonically through shock waves with s ...
) instead converts more internal energy into work on the surroundings (''i.e.'' less internal energy converted into heat); ''c.f.''
heat In thermodynamics, heat is defined as the form of energy crossing the boundary of a thermodynamic system by virtue of a temperature difference across the boundary. A thermodynamic system does not ''contain'' heat. Nevertheless, the term is ...
and
work (thermodynamics) In thermodynamics, work is one of the principal processes by which a thermodynamic system can interact with its surroundings and exchange energy. An exchange of energy is facilitated by a mechanism through which the system can spontaneously e ...
are equivalent forms of energy. See Heat of Combustion for a more thorough treatment of this topic. When a chemical compound is formed from its constituents, heat may either be absorbed or released. The quantity of heat absorbed or given off during transformation is called the
heat of formation In chemistry and thermodynamics, the standard enthalpy of formation or standard heat of formation of a compound is the change of enthalpy during the formation of 1 mole of the substance from its constituent elements in their reference state, wit ...
. Heats of formations for solids and gases found in explosive reactions have been determined for a temperature of 25 °C and atmospheric pressure, and are normally given in units of kilojoules per gram-molecule. A positive value indicates that heat is absorbed during the formation of the compound from its elements; such a reaction is called an endothermic reaction. In explosive technology only materials that are exothermic—that have a net liberation of heat and have a negative heat of formation—are of interest. Reaction heat is measured under conditions either of constant pressure or constant volume. It is this heat of reaction that may be properly expressed as the "heat of explosion."


Initiation of reaction

A chemical explosive is a compound or mixture which, upon the application of heat or shock, decomposes or rearranges with extreme rapidity, yielding much gas and heat. Many substances not ordinarily classed as explosives may do one, or even two, of these things. A reaction must be capable of being initiated by the application of shock, heat, or a
catalyst Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...
(in the case of some explosive chemical reactions) to a small portion of the mass of the explosive material. A material in which the first three factors exist cannot be accepted as an explosive unless the reaction can be made to occur when needed.


Fragmentation

Fragmentation is the accumulation and projection of particles as the result of a high explosives detonation. Fragments could originate from: parts of a structure (such as
glass Glass is a non-crystalline, often transparent, amorphous solid that has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most often formed by rapid cooling ( quenching ...
, bits of
structural material Structural engineering depends on the knowledge of materials and their properties, in order to understand how different materials resist and support loads. Common structural materials are: Iron Wrought iron Wrought iron is the simplest form ...
, or roofing material), revealed strata and/or various surface-level geologic features (such as loose
rock Rock most often refers to: * Rock (geology), a naturally occurring solid aggregate of minerals or mineraloids * Rock music, a genre of popular music Rock or Rocks may also refer to: Places United Kingdom * Rock, Caerphilly, a location in Wales ...
s,
soil Soil, also commonly referred to as earth or dirt Dirt is an unclean matter, especially when in contact with a person's clothes, skin, or possessions. In such cases, they are said to become dirty. Common types of dirt include: * Debri ...
, or
sand Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a textural class o ...
), the casing surrounding the explosive, and/or any other loose miscellaneous items not vaporized by the shock wave from the explosion. High velocity, low angle fragments can travel hundreds of metres with enough energy to initiate other surrounding high explosive items, injure or kill personnel, and/or damage vehicles or structures.


Notable examples


Chemical

* 1626
Wanggongchang Explosion The Wanggongchang Explosion ( zh, t=王恭廠大爆炸), also known as the Great Tianqi Explosion ( zh, t=天啟大爆炸, labels=no), Wanggongchang Calamity ( zh, t=王恭廠之變, labels=no) or Beijing Explosive Incident in the late Ming dy ...
* 1887 Nanaimo mine explosion * 1917
Halifax Explosion On the morning of 6 December 1917, the French cargo ship collided with the Norwegian vessel in the waters of Halifax, Nova Scotia, Canada. The ''Mont-Blanc'', laden with high explosives, caught fire and exploded, devastating the Richmond ...
* 1917 Battle of Messines * 1921
Oppau explosion The Oppau explosion occurred on September 21, 1921, when approximately 4,500 tonnes of a mixture of ammonium sulfate and ammonium nitrate fertilizer stored in a tower silo exploded at a BASF plant in Oppau, now part of Ludwigshafen, Germany, kil ...
*
1944 Bombay explosion The Bombay explosion (or Bombay docks explosion) occurred on 14 April 1944, in the Victoria Dock of Bombay, British India (now Mumbai, India) when the British freighter SS ''Fort Stikine'', carrying a mixed cargo of cotton bales, timber, oil, g ...
* 1944
Port Chicago disaster The Port Chicago disaster was a deadly munitions explosion of the ship SS ''E. A. Bryan'' that occurred on July 17, 1944, at the Port Chicago Naval Magazine in Port Chicago, California, United States. Munitions detonated while being loaded ...
* 1944
RAF Fauld explosion The RAF Fauld explosion was a military accident which occurred at 11:11am on Monday, 27 November 1944 at the RAF Fauld underground munitions storage depot in Staffordshire, England. It was one of the largest non-nuclear explosions in history ...
* 1947
Cádiz Explosion The Cádiz Explosion was a military accident which occurred at 9:45 pm, on 18 August 1947 at a storage depot in the Base de Defensas Submarinas (Submarine Defence Base) in Cádiz, Spain, when some 1,737 sea mines, torpedoes and depth charges (of ...
* 1947 Texas City disaster * 1960 Nedelin catastrophe * 1969 Soviet N1 rocket explosion * 1974 Flixborough disaster * 1998
PEPCON disaster On May 4, 1988, a fire followed by several explosions occurred at the Pacific Engineering and Production Company of Nevada (PEPCON) chemical plant in Henderson, Nevada. The disaster caused two fatalities, 372 injuries, and an estimated $100 mill ...
, Henderson, Nevada *
1988 Poole explosion On 21 June 1988, a large fire and explosion engulfed the BDH chemical plant in Poole, Dorset, England. 3,500 people were evacuated out of the town centre in the biggest peacetime evacuation the country had seen since World War II. Despite the inte ...
* 1994 Port Neal fertilizer plant explosion * 2001
AZF (factory) AZF (French initialism for ''AZote Fertilisant'', i.e. nitrogen fertiliser) was the name of a chemical factory in Toulouse, France, which exploded on 21 September 2001. The blast was equivalent to 20-40 tons of TNT, producing an earthquake with ...
* 2004 Ryongchon disaster * 2005 Hertfordshire Oil Storage Terminal fire *
2008 Gërdec explosions At approximately 12 p.m. local time on Saturday, March 15th, 2008, an ex-military ammunition depot in the village of Gërdec in the Vorë Municipality of Albania (14 kilometers from Tirana, the nation's capital), U.S and Albanian munitions expe ...
*
2009 Cataño oil refinery fire The 2009 Cataño oil refinery fire was a fire that began with an explosion on October 23, 2009, and was extinguished on October 25 at the Caribbean Petroleum Corporation (CAPECO) oil refinery and oil depot in Bayamón, Puerto Rico. While the ...
* 2013
West Fertilizer Company explosion On April 17, 2013, an ammonium nitrate explosion occurred at the West Fertilizer Company storage and distribution facility in West, Texas, United States ( north of Waco), while emergency services personnel were responding to a fire at the facili ...
*
2015 Tianjin explosions On 12 August 2015, a series of explosions at the Port of Tianjin in Tianjin, northern China, killed 173 people, according to official reports, and injured hundreds of others. The explosions occurred at a container storage station in the Bin ...
* 2020 Beirut explosion


Nuclear

*
Trinity test Trinity was the code name of the first detonation of a nuclear weapon. It was conducted by the United States Army at 5:29 a.m. on July 16, 1945, as part of the Manhattan Project. The test was conducted in the Jornada del Muerto desert abo ...
*
Ivy Mike Ivy Mike was the codename given to the first full-scale test of a thermonuclear device, in which part of the explosive yield comes from nuclear fusion. Ivy Mike was detonated on November 1, 1952, by the United States on the island of Elugelab ...
*
Castle Bravo Castle Bravo was the first in a series of high-yield thermonuclear weapon design tests conducted by the United States at Bikini Atoll, Marshall Islands, as part of '' Operation Castle''. Detonated on March 1, 1954, the device was the most powerful ...
*
Tsar Bomba The Tsar Bomba () ( code name: ''Ivan'' or ''Vanya''), also known by the alphanumerical designation "AN602", was a thermonuclear aerial bomb, and the most powerful nuclear weapon ever created and tested. Overall, the Soviet physicist Andrei ...
* Atomic bombings of Hiroshima and Nagasaki


Volcanic

* Santorini *
Krakatoa Krakatoa (), also transcribed (), is a caldera in the Sunda Strait between the islands of Java and Sumatra in the Indonesian province of Lampung. The caldera is part of a volcanic island group ( Krakatoa archipelago) comprising four islands. T ...
*
Mount St. Helens Mount St. Helens (known as Lawetlat'la to the indigenous Cowlitz people, and Loowit or Louwala-Clough to the Klickitat) is an active stratovolcano located in Skamania County, Washington, in the Pacific Northwest region of the United St ...
*
Mount Tambora Mount Tambora, or Tomboro, is an active stratovolcano in West Nusa Tenggara, Indonesia. Located on Sumbawa in the Lesser Sunda Islands, it was formed by the active subduction zones beneath it. Before 1815 eruption of Mount Tambora, 1815, its e ...
*
Mount Pinatubo Mount Pinatubo is an active stratovolcano in the Zambales Mountains, located on the tripoint boundary of the Philippine provinces of Zambales, Tarlac and Pampanga, all in Central Luzon on the northern island of Luzon. Its eruptive histor ...
*
Toba catastrophe theory The Youngest Toba eruption was a supervolcano eruption that occurred around 74,000 years ago at the site of present-day Lake Toba in Sumatra, Indonesia. It is one of the Earth's largest known explosive eruptions. The Toba catastrophe theory ho ...
* Yellowstone Caldera


Stellar

*
List of supernovae This is a list of supernovae that are of historical significance. These include supernovae that were observed prior to the availability of photography, and individual events that have been the subject of a scientific paper that contributed to supe ...


Etymology

Classical Latin means "to hiss a bad actor off the stage", "to drive an actor off the stage by making noise", from (“out”) + (“to clap; to applaud”). The modern meaning developed later: wikt:explode#Etymology * Classical Latin: "to drive an actor off the stage by making noise" hence meaning "to drive out" or "to reject" In English: * Around 1538: "drive out or off by clapping" (originally theatrical) * Around 1660: "drive out with violence and sudden noise" * Around 1790: "go off with a loud noise" * Around 1882: first use as "bursting with destructive force"


See also


References

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