Mushroom cloud

A mushroom cloud is a distinctive pyrocumulus mushroom-shaped cloud of debris/smoke and usually condensed water vapor resulting from a large explosion. The effect is most commonly associated with a nuclear explosion, but any sufficiently energetic detonation or deflagration will produce the same effect. They can be caused by powerful conventional weapons, like thermobaric weapons, including the ATBIP and GBU-43/B Massive Ordnance Air Blast. Some volcanic eruptions and impact events can produce natural mushroom clouds.

Mushroom clouds result from the sudden formation of a large volume of lower-density gases at any altitude, causing a Rayleigh–Taylor instability. The buoyant mass of gas rises rapidly, resulting in turbulent vortices curling downward around its edges, forming a temporary vortex ring that draws up a central column, possibly with smoke, debris, and/or condensed water vapor to form the "mushroom stem". The mass of gas plus entrained moist air eventually reaches an altitude where it is no longer of lower density than the surrounding air; at this point, it disperses, drifting back down (see fallout). The stabilization altitude depends strongly on the profiles of the temperature, dew point, and wind shear in the air at and above the starting altitude.

Ascending cloud from Redoubt Volcano from an eruption on April 21, 1990. The mushroom-shaped plume rose from avalanches of hot debris (pyroclastic flows) that cascaded down the north flank of the volcano.
Mushroom cloud from the atomic bombing of Nagasaki, Japan on August 9, 1945.

Origin of the term

Vue du siege de Gibraltar et explosion des batteries flottantes 1782.jpeg
Vue du siège de Gibraltar et explosion des batteries flottantes View of the Siege of Gibraltar and the Explosion of the Floating Batteries, artist unknown, c.1782

Although the term appears to have been coined at the start of the 1950s, mushroom clouds generated by explosions were being described centuries before the atomic era. A contemporary aquatint by an unknown artist of the 1782 Franco-Spanish attack on Gibraltar shows one of the attacking force's floating batteries exploding with a mushroom cloud, after the British defenders set it ablaze by firing heated shot. The 1917 Halifax Explosion produced one. The Times published a report on 1 October 1937 of a Japanese attack on Shanghai in China which generated "a great mushroom of smoke". During World War II, descriptions of mushroom clouds were relatively common.

The atomic bomb cloud over Nagasaki, Japan was described in The Times of London of 13 August 1945 as a "huge mushroom of smoke and dust". On 9 September 1945, The New York Times published an eyewitness account of the Nagasaki bombing, written by William L. Laurence, the official newspaper correspondent of the Manhattan Project, who accompanied one of the three aircraft that made the bombing run. He wrote of the bomb producing a "pillar of purple fire", out of the top of which came "a giant mushroom that increased the height of the pillar to a total of 45,000 feet".[1]

Later in 1946, the Operation Crossroads nuclear bomb tests were described as having a "cauliflower" cloud, but a reporter present also spoke of "the mushroom, now the common symbol of the atomic age". Mushrooms have traditionally been associated both with life and death, food and poison, making them a more powerful symbolic connection than, say, the "cauliflower" cloud.[2]


Mushroom cloud
Inside a rising mushroom cloud: denser air rapidly forces itself into the bottom center of the toroidal fireball, which turbulently mixes into the familiar cloud appearance.

Mushroom clouds are formed by many sorts of large explosions under earth's gravity, but they are best known for their appearance after nuclear detonations. Without gravity, the explosive's by-product gases would remain spherical. Nuclear weapons are usually detonated above the ground (not upon impact, because some of the energy would be dissipated by the ground motions), to maximize the effect of their spherically expanding fireball and blast wave. Immediately after the detonation, the fireball begins to rise into the air, acting on the same principle as a hot-air balloon.

One way to analyze the motion, once the hot gas has cleared the ground sufficiently, is as a 'spherical cap bubble',[3] as this gives agreement between the rate of rise and observed diameter.

Castle Bravo Blast
Castle Bravo, March 1, 1954 >15 Mt, showing multiple condensation rings and several ice caps.

As it rises, a Rayleigh–Taylor instability is formed, and air is drawn upwards and into the cloud (similar to the updraft of a chimney), producing strong air currents known as "afterwinds", while, inside the head of the cloud, the hot gases rotate in a toroidal shape. When the detonation altitude is low enough, these afterwinds will draw in dirt and debris from the ground below to form the stem of the mushroom cloud.

After the mass of hot gases reaches its equilibrium level, the ascent stops, and the cloud starts flattening the characteristic mushroom shape, usually aided by surface growth due to the decaying turbulence.

Nuclear mushroom clouds

Nuclear detonations produced high above the ground might not create mushroom clouds with a stem. The heads of the clouds themselves consist of highly radioactive particles, primarily the fission products and other weapon debris aerosols, and are usually dispersed by the wind, though weather patterns (especially rain) can produce problematic nuclear fallout.[4]

Detonations significantly below ground level or deep below the water (for instance, nuclear depth charges) also do not produce mushroom clouds, as the explosion causes the vaporization of a huge amount of earth and water in these instances, creating a bubble which then collapses in on itself; in the case of a less deep underground explosion, this produces a subsidence crater. Detonations underwater but near the surface produce a pillar of water, which, in collapsing, forms a cauliflower-like shape, which is easily mistaken for a mushroom cloud (such as in the well-known pictures of the Crossroads Baker test). Underground detonations at low depth produce a mushroom cloud and a base surge, two different distinct clouds. The amount of radiation vented into the atmosphere decreases rapidly with increasing detonation depth.

With surface and near-surface air bursts, the amount of debris lofted into the air decreases rapidly with increasing burst altitude. At burst altitudes of approximately 7 meters/kiloton13, a crater is not formed, and correspondingly lower amounts of dust and debris are produced. The fallout-reducing height, above which the primary radioactive particles consist mainly of the fine fireball condensation, is approximately 55 meters/kiloton0.4.[4] However, even at these burst altitudes, fallout may be formed by a number of mechanisms.

Mushroom cloud size as a function of yield.

The distribution of radiation in the mushroom cloud varies with the yield of the explosion, type of weapon, fusion/fission ratio, burst altitude, terrain type, and weather. In general, lower-yield explosions have about 90% of their radioactivity in the mushroom head and 10% in the stem. In contrast, megaton-range explosions tend to have most of their radioactivity in the lower third of the mushroom cloud.[5]

At the moment of the explosion, the fireball is formed. The ascending, roughly spherical mass of hot, incandescent gases changes shape due to atmospheric friction and cools its surface by energy radiation, turning from a sphere to a violently rotating spheroidal vortex. A Rayleigh–Taylor instability is formed as the underneath cool air initially pushes the bottom fireball gases into an inverted cup shape. This causes turbulence and a vortex that sucks more air into its center, creating external afterwinds and cooling itself. The speed of its rotating slows down as it cools, and may stop entirely during later phases. The vaporized parts of the weapon and ionized air cool into visible gases, forming the early cloud; the white-hot vortex core becomes yellow, then dark red, then loses visible incandescence. With further cooling, the bulk of the cloud fills in as atmospheric moisture condenses. As the cloud ascends and cools, its buoyancy lessens, and its ascent slows.

If the size of the fireball is comparable to the atmospheric density scale height, the whole cloud rise will be ballistic, overshooting a large volume of overdense air to greater altitudes than the final stabilization altitude. Significantly smaller fireballs produce clouds with buoyancy-governed ascent.

After reaching the tropopause, the bottom of the region of strong static stability, the cloud tends to slow its ascent and spread out. If it contains sufficient energy, the central part of it may continue rising up into the stratosphere as an analog of a standard thunderstorm.[6] A mass of air ascending from the troposphere to the stratosphere leads to the formation of acoustic gravity waves, virtually identical to those created by intense stratosphere-penetrating thunderstorms. Smaller-scale explosions penetrating the tropopause generate waves of higher frequency, classified as infrasound.

The explosion raises a large amount of moisture-laden air from lower altitudes. As the air rises, its temperature drops, and its water vapour first condenses as water droplets, and later freezes as ice crystals. The phase changes release latent heat, heating the cloud and driving it to yet higher altitudes.

Bomba atomica
The evolution of a nuclear mushroom cloud; 19 kt at 120 m • kt −​13. Tumbler-Snapper Dog. The sandy Nevada desert soil is "popcorned" by the intense flash of light emitted by the prompt supercriticality event and this "popcorning effect" results in more soil being lofted into the stem of the mushroom cloud, than would otherwise be the case, if the device had been placed above a more typical surface or soil.

A mushroom cloud undergoes several phases of formation.[7]

  • Early time, the first ≈20 seconds, when the fireball forms and the fission products mix with the material aspired from the ground or ejected from the crater. The condensation of evaporated ground occurs in first few seconds, most intensely during fireball temperatures between 3500–4100 K.[8]
  • Rise and stabilization phase, 20 seconds to 10 minutes, when the hot gases rise up and early large fallout is deposited.
  • Late time, until about 2 days later, when the airborne particles are being distributed by wind, deposited by gravity, and scavenged by precipitation.

The shape of the cloud is influenced by the local atmospheric conditions and wind patterns. The fallout distribution is predominantly a downwind plume. However, if the cloud reaches the tropopause, it may spread against the wind, because its convection speed is higher than the ambient wind speed. At the tropopause, the cloud shape is roughly circular and spread out.

The initial color of some radioactive clouds can be colored red or reddish-brown, due to presence of nitrogen dioxide and nitric acid, formed from initially ionized nitrogen, oxygen, and atmospheric moisture. In the high-temperature, high-radiation environment of the blast, ozone is also formed. It is estimated that each megaton of yield produces about 5000 tons of nitrogen oxides.[9] Yellow and orange hues have also been described. This reddish hue is later obscured by the white colour of water/ice clouds, condensing out of the fast-flowing air as the fireball cools, and the dark colour of smoke and debris sucked into the updraft. The ozone gives the blast its characteristic corona discharge-like smell.[10]

The droplets of condensed water gradually evaporate, leading to the cloud's apparent disappearance. The radioactive particles, however, remain suspended in the air, and the now-invisible cloud continues depositing fallout along its path.

The stem of the cloud is gray to brown in a groundburst, as large amounts of dust, dirt, soil, and debris are sucked into the mushroom cloud. Airbursts produce white, steamy stems. Groundbursts produce dark mushroom clouds, containing irradiated material from the ground in addition to the bomb and its casing, and therefore produce more radioactive fallout, with larger particles that readily deposit locally.

A higher-yield detonation can carry the nitrogen oxides from the burst high enough in atmosphere to cause significant depletion of the ozone layer.

A double mushroom, with two levels, can be formed under certain conditions. For example, the Buster-Jangle Sugar shot formed the first head from the blast itself, followed by another one generated by the heat from the hot, freshly formed crater.[11]

The fallout itself may appear as dry, ash-like flakes, or as particles too small to be visible; in the latter case, the particles are often deposited by rain. Large amounts of newer, more radioactive particles deposited on skin can cause beta burns, often presenting as discolored spots and lesions on the backs of exposed animals.[12] The fallout from the Castle Bravo test had the appearance of white dust and was nicknamed Bikini snow; the tiny white flakes resembled snowflakes, stuck to surfaces, and had a salty taste. 41.4% of the fallout from the Operation Wigwam test consisted of irregular opaque particles, slightly over 25% of particles with transparent and opaque areas, approximately 20% of microscopic marine organisms, and 2% of microscopic radioactive threads of unknown origin.[11]

Cloud composition

The mushroom cloud from Buster-Jangle Charlie, yield 14 kilotons (at 143 m • kt −​13), during the initial phase of stem formation. The toroidal fireball is visible at the top, a condensation cloud is forming in the middle due to intense updrafts of moist air, and the forming partial stem can be seen below. The cloud exhibits the reddish-brown hue of nitrogen oxides.

The cloud contains three main classes of material: the remains of the weapon and its fission products, the material acquired from the ground (only significant for burst altitudes below the fallout-reducing altitude, which depends on the weapon yield), and water vapour. The bulk of the radiation contained in the cloud consists of the nuclear fission products; neutron activation products from the weapon materials, air, and the ground debris form only a minor fraction. Neutron activation starts during the neutron burst at the instant of the blast itself, and the range of this neutron burst is limited by the absorption of the neutrons as they pass through the Earth's atmosphere.

Most of the radiation is created by the fission products. Thermonuclear weapons produce a significant part of their yield from nuclear fusion. Fusion products are typically non-radioactive. The degree of radiation fallout production is therefore measured in kilotons of fission. The Tsar Bomba, which produced 97% of its 50-megaton yield from fusion, was a very clean weapon compared to what would typically be expected of a weapon of its yield (although it still produced 1.5 megatons of its yield from fission), as its fusion tamper was made of lead instead of uranium-238; otherwise, its yield would have been 100 megatons with 51 of those from fission. Were it to be detonated at or near the surface, its fallout would comprise fully one-quarter of all the fallout from every nuclear weapon test, combined.

Initially, the fireball contains a highly ionized plasma consisting only of atoms of the weapon, its fission products, and atmospheric gases of adjacent air. As the plasma cools, the atoms react, forming fine droplets and then solid particles of oxides. The particles coalesce to larger ones, and deposit on surface of other particles. Larger particles usually originate from material aspired into the cloud. Particles aspired while the cloud is still hot enough to melt them mix with the fission products throughout their volume. Larger particles get molten radioactive materials deposited on their surface. Particles aspired into the cloud later, when its temperature is low enough, do not become significantly contaminated. Particles formed only from the weapon itself are fine enough to stay airborne for a long time and become widely dispersed and diluted to non-hazardous levels. Higher-altitude blasts which do not aspire ground debris, or which aspire dust only after cooling enough and where the radioactive fraction of the particles is therefore small, cause much smaller degree of localized fallout than lower-altitude blasts with larger radioactive particles formed.

The concentration of condensation products is the same for the small particles and for the deposited surface layers of larger particles. About 100 kg of small particles are formed per kiloton of yield. The volume, and therefore activity, of the small particles is almost three orders of magnitude lower than the volume of the deposited surface layers on larger particles.

For higher-altitude blasts, the primary particle forming processes are condensation and subsequent coagulation. For lower-altitude and ground blasts, with involvement of soil particles, the primary process is deposition on the foreign particles.

A low-altitude detonation produces a cloud with a dust loading of 100 tons per megaton of yield. A ground detonation produces clouds with about three times as much dust. For a ground detonation, approximately 200 tons of soil per kiloton of yield is melted and comes in contact with radiation.[8]

The fireball volume is the same for a surface or an atmospheric detonation. In the first case, the fireball is a hemisphere instead of a sphere, with a correspondingly larger radius.[8]

The particle sizes range from submicrometer- and micrometer-sized (created by condensation of plasma in the fireball), through 10–500 micrometers (surface material agitated by the blast wave and raised by the afterwinds), to millimeter and above (crater ejecta). The size of particles together with the altitude they are carried to, determines the length of their stay in the atmosphere, as larger particles are subject to dry precipitation. Smaller particles can be also scavenged by precipitation, either from the moisture condensing in the cloud itself or from the cloud intersecting with a rain cloud. The fallout carried down by rain is known as rain-out if scavenged during raincloud formation, washout if absorbed into already formed falling raindrops.[13]

Particles from air bursts are smaller than 10–25 micrometers, usually in the submicrometer range. They are composed mostly of iron oxides, with smaller proportion of aluminium oxide, and uranium and plutonium oxides. Particles larger than 1–2 micrometers are very spherical, corresponding to vaporized material condensing into droplets and then solidifying. The radioactivity is evenly distributed throughout the particle volume, making total activity of the particles linearly dependent on particle volume.[8] About 80% of activity is present in more volatile elements, which condense only after the fireball cools to considerable degree. For example, strontium-90 will have less time to condense and coalesce into larger particles, resulting in greater degree of mixing in the volume of air and smaller particles.[14] The particles produced immediately after the burst are small, with 90% of the radioactivity present in particles smaller than 300 nanometers. These coagulate with stratospheric aerosols. Coagulation is more extensive in the troposphere, and, at ground level, most activity is present in particles between 300 nm and 1 µm. The coagulation offsets the fractionation processes at particle formation, evening out isotopic distribution.

For ground and low-altitude bursts, the cloud contains also vaporized, melted and fused soil particles. The distribution of activity through the particles depends on their formation. Particles formed by vaporization-condensation have activity evenly distributed through volume as the air-burst particles. Larger molten particles have the fission products diffused through the outer layers, and fused and non-melted particles that were not heated sufficiently but came in contact with the vaporized material or scavenged droplets before their solidification have a relatively thin layer of high activity material deposited on their surface. The composition of such particles depends on the character of the soil, usually a glass-like material formed from silicate minerals. The particle sizes do not depend on the yield but instead on the soil character, as they are based on individual grains of the soil or their clusters. Two types of particles are present, spherical, formed by complete vaporization-condensation or at least melting of the soil, with activity distributed evenly through the volume (or with a 10–30% volume of inactive core for larger particles between 0.5–2 mm), and irregular-shaped particles formed at the edges of the fireball by fusion of soil particles, with activity deposited in a thin surface layer. The amount of large irregular particles is insignificant.[8] Particles formed from detonations above, or in, the ocean, will contain short-lived radioactive sodium isotopes, and salts from the sea water. Molten silica is a very good solvent for metal oxides and scavenges small particles easily; explosions above silica-containing soils will produce particles with isotopes mixed through their volume. In contrast, coral debris, based on calcium carbonate, tends to adsorb radioactive particles on its surface.[14]

The elements undergo fractionation during particle formation, due to their different volatility. Refractory elements (Sr, Y, Zr, Nb, Ba, La, Ce, Pr, Nd, Pm) form oxides with high boiling points; these precipitate the fastest and at the time of particle solidification, at temperature of 1400 °C, are considered to be fully condensed. Volatile elements (Kr, Xe, I, Br) are not condensed at that temperature. Intermediate elements have their (or their oxides) boiling points close to the solidification temperature of the particles (Rb, Cs, Mo, Ru, Rh, Tc, Sb, Te). The elements in the fireball are present as oxides, unless the temperature is above the decomposition temperature of a given oxide. Less refractory products condense on surfaces of solidified particles. Isotopes with gaseous precursors solidify on the surface of the particles as they are produced by decay.

The largest, and therefore the most radioactive particles, are deposited by fallout in the first few hours after the blast. Smaller particles are carried to higher altitudes and descend more slowly, reaching ground in a less radioactive state as the isotopes with the shortest half-lives decay the fastest. The smallest particles can reach the stratosphere and stay there for weeks, months, or even years, and cover an entire hemisphere of the planet via atmospheric currents. The higher danger, short-term, localized fallout is deposited primarily downwind from the blast site, in a cigar-shaped area, assuming a wind of constant strength and direction. Crosswinds, changes in wind direction, and precipitation are factors that can greatly alter the fallout pattern.[15]

The condensation of water droplets in the mushroom cloud depends on the amount of condensation nuclei. Too many condensation nuclei actually inhibit condensation, as the particles compete for a relatively insufficient amount of water vapor.

Chemical reactivity of the elements and their oxides, ion adsorption properties, and compound solubility influence particle distribution in the environment after deposition from the atmosphere. Bioaccumulation influences the propagation of fallout radioisotopes in the biosphere.


The primary fallout hazard is gamma radiation from short-lived radioisotopes, which represent the bulk of activity. Within 24 hours after the burst, the fallout gamma radiation level drops 60 times. Longer-life radioisotopes, typically caesium-137 and strontium-90, present a long-term hazard. Intense beta radiation from the fallout particles can cause beta burns to people and animals coming in contact with the fallout shortly after the blast. Ingested or inhaled particles cause an internal dose of alpha and beta radiation, which may lead to long-term effects, including cancer.

The neutron irradiation of the atmosphere itself produces a small amount of activation, mainly as long-lived carbon-14 and short-lived argon-41. The elements most important for induced radioactivity for sea water are sodium-24, chlorine, magnesium, and bromine. For ground bursts, the elements of concern are aluminium-28, silicon-31, sodium-24, manganese-56, iron-59, and cobalt-60.

The bomb casing can be a significant sources of neutron-activated radioisotopes. The neutron flux in the bombs, especially thermonuclear devices, is sufficient for high-threshold nuclear reactions. The induced isotopes include cobalt-60, 57 and 58, iron-59 and 55, manganese-54, zinc-65, yttrium-88, and possibly nickel-58 and 62, niobium-63, holmium-165, iridium-191, and short-lived manganese-56, sodium-24, silicon-31, and aluminium-28. Europium-152 and 154 can be present, as well as two nuclear isomers of rhodium-102. During the Operation Hardtack, tungsten-185, 181 and 187 and rhenium-188 were produced from elements added as tracers to the bomb casings, to allow identification of fallout produced by specific explosions. Antimony-124, cadmium-109, and cadmium-113m are also mentioned as tracers.[8]

The most significant radiation sources are the fission products from the primary fission stage, and in the case of fission-fusion-fission weapons, from the fission of the fusion stage uranium tamper. Many more neutrons per unit of energy are released in a thermonuclear explosion in comparison with a purely fission yield influencing the fission products composition. For example, the uranium-237 isotope is a unique thermonuclear explosion marker, as it is produced by a (n,2n) reaction from uranium-238, with the minimal neutron energy needed being about 5.9 MeV. Considerable amounts of neptunium-239 and uranium-237 are indicators of a fission-fusion-fission explosion. Minor amounts of uranium-240 are also formed, and capture of large numbers of neutrons by individual nuclei leads to formation of small but detectable amounts of higher transuranium elements, e.g. einsteinium-255 and fermium-255.[8]

One of the important fission products is krypton-90, a radioactive noble gas. It diffuses easily in the cloud, and undergoes two decays to rubidium-90 and then strontium-90, with half-lives of 33 seconds and 3 minutes. The noble gas nonreactivity and rapid diffusion is responsible for depletion of local fallout in Sr-90, and corresponding Sr-90 enrichment of remote fallout.[16]

The radioactivity of the particles decreases with time, with different isotopes being significant at different timespans. For soil activation products, aluminium-28 is the most important contributor during the first 15 minutes. Manganese-56 and sodium-24 follow until about 200 hours. Iron-59 follows at 300 hours, and after 100–300 days, the significant contributor becomes cobalt-60.

Radioactive particles can be carried for considerable distances. Radiation from the Trinity test was washed out by a rainstorm in Illinois. This was deduced, and the origin traced, when Eastman Kodak found x-ray films were being fogged by cardboard packaging produced in the Midwest. Unanticipated winds carried lethal doses of Castle Bravo fallout over the Rongelap Atoll, forcing its evacuation. The crew of Daigo Fukuryu Maru, a Japanese fishing boat located outside of the predicted danger zone, was also affected. Strontium-90 found in worldwide fallout later led to the Partial Test Ban Treaty.[14]

Fluorescent glow

The intense radiation in the first seconds after the blast may cause an observable aura of fluorescence, the blue-violet-purple glow of ionized oxygen and nitrogen out to a significant distance from the fireball, surrounding the head of the forming mushroom cloud.[17][18][19] This light is most easily visible at night or under conditions of weak daylight.[4] The brightness of the glow decreases rapidly with elapsed time since the detonation, becoming only barely visible after a few tens of seconds.[20]

Condensation effects

Nuclear mushroom clouds are often accompanied by short-lived vapour clouds, known variously as "Wilson clouds", condensation clouds, or vapor rings. The "negative phase" following the positive overpressure behind a shock front causes a sudden rarefaction of the surrounding medium. This low pressure region causes an adiabatic drop in temperature, causing moisture in the air to condense in an outward moving shell surrounding the explosion. When the pressure and temperature return to normal, the Wilson cloud dissipates.[21] Scientists observing the Operation Crossroads nuclear tests in 1946 at Bikini Atoll named that transitory cloud a "Wilson cloud" because of its visual similarity to a Wilson cloud chamber; the cloud chamber uses condensation from a rapid pressure drop to mark the tracks of electrically charged subatomic particles. Analysts of later nuclear bomb tests used the more general term "condensation cloud" in preference to "Wilson cloud".

The same kind of condensation is sometimes seen above the wings of jet aircraft at low altitude in high-humidity conditions. The top of a wing is a curved surface. The curvature (and increased air velocity) causes a reduction in air pressure, as given by Bernoulli's Law. This reduction in air pressure causes cooling, and when the air cools past its dew point, water vapour condenses out of the air, producing droplets of water, which become visible as a white cloud. In technical terms, the "Wilson cloud" is also an example of the Prandtl–Glauert singularity in aerodynamics.

The shape of the shock wave is influenced by variation of the speed of sound with altitude, and the temperature and humidity of different atmospheric layers determines the appearance of the Wilson clouds. Condensation rings around or above the fireball are a commonly observed feature. Rings around the fireball may become stable, becoming rings around the rising stem. Higher-yield explosions cause intense updrafts, where air speeds can reach 300 miles per hour (480 km/h). The entrainment of higher-humidity air, combined with the associated drop in pressure and temperature, leads to the formation of skirts and bells around the stem. If the water droplets become sufficiently large, the cloud structure they form may become heavy enough to descend; in this way, a rising stem with a descending bell around it can be produced. Layering of humidity in the atmosphere, responsible for the appearance of the condensation rings as opposed to a spherical cloud, also influences the shape of the condensation artifacts along the stem of the mushroom cloud, as the updraft causes laminar flow. The same effect above the top of the cloud, where the expansion of the rising cloud pushes a layer of warm, humid, low-altitude air upwards into cold, high-altitude air, first causes the condensation of water vapour out of the air and then causes the resulting droplets to freeze, forming ice caps (or icecaps), similar in both appearance and mechanism of formation to scarf clouds.

The resulting composite structures can become very complex. The Castle Bravo cloud had, at various phases of its development, 4 condensation rings, 3 ice caps, 2 skirts, and 3 bells.

The Castle Bravo test

The mushroom cloud from the 15-megaton Castle Bravo hydrogen bomb test, showing multiple condensation rings, March 1, 1954.

Castle romeo2

The mushroom cloud from the 11-megaton Castle Romeo hydrogen bomb test, showing a prominent condensation ring.

Castle Union

The mushroom cloud from the 6.9-megaton Castle Union hydrogen bomb test, showing multiple condensation rings.

Crossroads baker explosion

The water column from the 21-kiloton Crossroads Baker test, involving a nuclear underwater explosion, showing a prominent, spherical Wilson cloud.

Greenhouse George

The mushroom cloud from the 225-kiloton Greenhouse George test, showing a well-developed bell.

The formation of a mushroom cloud from a nuclear test; Tumbler-Snapper Dog. The streamers of smoke seen to the left of the explosion at detonation are vertical smoke flares used to observe the shockwave from the explosion, and are unrelated to the mushroom cloud.
The formation of a mushroom cloud from a nuclear test; Tumbler-Snapper Dog. The streamers of smoke seen to the left of the explosion at detonation are vertical smoke flares used to observe the shockwave from the explosion, and are unrelated to the mushroom cloud.


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Chain Reaction (sculpture)

Chain Reaction is a peace monument and public art sculpture composed of a metal framework of stainless steel and fiberglass surrounded by concrete, depicting a mushroom cloud created by a nuclear explosion. Designed by American editorial cartoonist Paul Conrad and built by Peter M. Carlson, the 5.5-ton, 8-meter (26-foot) high sculpture was installed in 1991 adjacent to the Santa Monica Civic Center in Santa Monica, California.An inscription at the base of the sculpture reads, "This is a statement of peace. May it never become an epitaph." The theme of the sculpture reflects the subject of nuclear disarmament. UCLA professor Paul Von Blum places the sculpture in the category of late 20th and early 21st century contemporary American public political artwork in the tradition of commemorative works throughout the United States, calling the work "a powerful warning about the continuing dangers of nuclear war".Conrad first expressed interest in building the sculpture in either Beverly Hills or Santa Monica in 1988. He built the sculpture with the help of an anonymous donation of $250,000 and donated the sculpture to the city of Santa Monica after it was approved by the city. It was later revealed that the donation came from philanthropist Joan Kroc, widow of Ray Kroc, the founder of the McDonald's corporation. Joan Kroc spent millions campaigning for nuclear disarmament in the 1980s. In 2012, the sculpture became the first work of public art designated as a historic landmark in the City of Santa Monica.

Condensation cloud

A transient condensation cloud, also called Wilson cloud, is observable at large explosions in humid air.

When a nuclear weapon or a large amount of a conventional explosive is detonated in sufficiently humid air, the "negative phase" of the shock wave causes a rarefaction (reduction in density) of the air surrounding the explosion, but not contained within it. This rarefaction results in a temporary cooling of that air, which causes a condensation of some of the water vapor contained in it. When the pressure and the temperature return to normal, the Wilson cloud dissipates.Since heat does not leave the affected air mass, this change of pressure is adiabatic, with an associated change of temperature. In humid air, the drop in temperature in the most rarefied portion of the shock wave can bring the air temperature below its dew point, at which moisture condenses to form a visible cloud of microscopic water droplets. Since the pressure effect of the wave is reduced by its expansion (the same pressure effect is spread over a larger radius), the vapor effect also has a limited radius. Such vapor can also be seen in low pressure regions during high–g subsonic maneuvers of aircraft in humid conditions.

Scientists observing the Operation Crossroads nuclear tests in 1946 at Bikini Atoll named that transitory cloud a "Wilson cloud" because of its similarity to the appearance of the inside of a Wilson cloud chamber, an instrument they would have been familiar with. (The cloud chamber effect is caused by a temporary reduction in pressure in a closed system and marks the tracks of electrically-charged sub-atomic particles.) Analysts of later nuclear bomb tests used the more general term condensation cloud.

The shape of the shock wave, influenced by different speed in different altitudes, and the temperature and humidity of different atmospheric layers determines the appearance of the Wilson clouds. During nuclear tests, condensation rings around or above the fireball are commonly observed. Rings around the fireball may become stable and form rings around the rising stem of the mushroom cloud.

The lifetime of the Wilson cloud during nuclear air bursts can be shortened by the thermal radiation from the fireball, which heats the cloud above the dew point and evaporates the droplets.

The same kind of condensation cloud is sometimes seen above the wings of aircraft in a moist atmosphere. The top of a wing has a reduction of air pressure as part of the process of generating lift. This reduction in air pressure causes a cooling, just as above, and the condensation of water vapor. Hence, the small, transient clouds that appear.

The vapor cone of a transonic aircraft is another example of a condensation cloud.

Divine Strake

Divine Strake was the official designation for a large-yield, non-nuclear, high-explosive test that was planned for the Nevada National Security Site, formerly the Nevada Test Site. Following its announcement, the test generated great controversy, centering on two issues: its potential value in developing a nuclear "bunker buster" warhead, and the possibility that the mushroom cloud generated by the explosion could carry large amounts of radioactive dust deposited at the Test Site over years of nuclear testing.

On February 22, 2007 the Defense Threat Reduction Agency (DTRA) officially cancelled the experiment.


Earthandsky (stylized in all caps; read as Earth and Sky) is the sixth studio album by American metalcore band Of Mice & Men. It was released on September 27, 2019 through Rise Records. The album was produced by Josh Wilbur and is the follow-up to the group's fifth album, Defy (2018).


Elugelab, or Elugelap (Marshallese: Āllokļap, [ælʲːe͡oɡʷ(ɔ͡ʌ)ɫɑ͡æpʲ]), was an island, part of the Enewetak Atoll in the Marshall Islands. It was enlarged, and then destroyed by the world's first true hydrogen bomb test on 1 November 1952, a test which was codenamed shot "Mike" of Operation Ivy. Prior to being enlarged and subsequently destroyed, the island was described as "just another small naked island of the atoll".The fireball created by Ivy Mike had a maximum radius of 2.9 to 3.28 km (1.80 to 2.04 mi). This maximum is reached a number of seconds after the detonation and during this time the hot fireball invariably rises due to buoyancy. While still relatively close to the ground, the fireball had yet to reach its maximum dimensions and was thus approximately "three and one quarter" miles (5.2 km) wide.The detonation produced a crater 6,240 feet (1.90 km) in diameter and 164 feet (50 m) deep where Elugelab had once been; the blast and water waves from the explosion (some waves up to twenty feet high) stripped the test islands clean of vegetation, as observed by a helicopter survey within 60 minutes after the test, by which time the mushroom cloud had blown away. The island "became dust and ash, pulled upward to form a mushroom cloud that rose about twenty-seven miles into the sky. According to Eric Schlosser, all that remained of Elugelab was a circular crater filled with seawater, more than a mile in diameter and "fifteen storeys deep". The blast yielded 10.4 megatons of explosive energy, 700 times the energy that leveled central Hiroshima.Aerial footage of Elugelab and adjacent islands well before Mike shot at a time prior to the connecting causeway being created is available, as is footage after the causeway was finished that supported the diagnostic Krause-Ogle box light pipe system, with numerous trees removed in preparation of the shot also plainly evident, along with footage of the aforementioned helicopter survey of the Mike crater soon after the detonation, and finally, high-altitude footage of the crater accompanied with details of its depth—"175 feet deep"—equivalent to the height of a "17-storey building" and with an area large enough to accommodate about "14 Pentagon buildings".The detonation also collapsed some natural crevices in the reef, some distance away from the rim of the crater.Full radioecology recovery surveys were documented before and after each test series. For a brief online introduction into some of these studies—with specific reference to the ecological effects of the 1.69-megaton Operation Castle Nectar shot, detonated in 1954 on a barge just north east of the crater of the 10.4-megaton Ivy Mike thermonuclear test - see [1] a report by the University of Washington's Laboratory of Radiation Biology and [2].

Emanuele Ottolenghi

Emanuele Ottolenghi, a political scientist, is a Senior Fellow with the Foundation for the Defense of Democracies in Washington, DC. Previously, he ran the Brussels-based AJC Transatlantic Institute. He has taught at the Oxford Centre for Hebrew and Jewish Studies, as well as the Middle East Centre of St. Antony’s College, Oxford. He earned a Ph.D. from the Hebrew University and an undergraduate degree from the University of Bologna.

Ottolenghi has written about Middle East issues for Commentary, The Daily Mirror, The Guardian, National Review Online, Newsday, the Jewish Chronicle, and the Middle East Quarterly, as well as European publications: Corriere del Ticino, il Foglio, Libero, Il Riformista, Liberal, Standpoint, L'Unità, and Die Welt.

He has expertise on antisemitism, Iran, Israel, Italy, and terrorism. He is the author of five books:

The Pasdaran: Inside Iran's Islamic Revolutionary Guards Corps (Washington, FDD Press: 2011).

Iran: the Looming Crisis (London, Profile Books: 2010).

Under a Mushroom Cloud: Europe, Iran and the Bomb (London, Profile Books: 2009).

La Bomba Iraniana (Turin, Lindau: 2008).

Autodafe': L'Europa, gli ebrei e l'antisemitismo (Turin, Lindau: 2007).

Fairchild K-20

The K-20 is an aerial photography camera used during World War II, e.g., from the Enola Gay's tail gunner position of the nuclear mushroom cloud over Hiroshima. Designed by Fairchild Camera and Instrument, approximately 15,000 were manufactured under licence for military contract by Folmer Graflex Corporation in Rochester, New York between 1941 and 1945.

The K-20 uses a 5.25"×20 to 5.25"×200 foot roll film, with an image size of 4×5 inches. Lenses were 6 3/8" f/4.5 with an adjustable diaphragm and were non interchangeable, these were made by Kodak, Ilex, or Bausch & Lomb, as available at the time of order. The camera featured the use of a vacuum to keep the film flat.

Earlier aerial cameras, from the World War I era, included the Kodak K1, with focal plane shutter, the Fairchild K3, K3A, K3B etc., with in-lens shutter to eliminate distortion, K5 etc., some of which used individual glass plates, some individual sheet film, and some roll film.

Similar cameras, from the World War II era are: K17, K18, K19, K21, K22, F20, F40, F56, etc., many making 9"×9" or 9"×18" images using 9"+ roll film.

George R. Caron

Technical Sergeant George Robert "Bob" Caron (October 31, 1919 – June 3, 1995) was the tail gunner, the only defender of the twelve crewmen, aboard the B-29 Enola Gay during the historic bombing of the Japanese city of Hiroshima on 6 August 1945. Facing the rear of the B-29, his vantage point made him the first man to witness the cataclysmic growth of the mushroom cloud over Hiroshima.

Caron was also the only photographer aboard, and took photographs as the mushroom cloud ascended. Of the four 509th Composite Group aircraft assigned to the Hiroshima bombing, Caron's camera and two others captured the explosion on film. Immediately before the mission, the 509th's photography officer, Lieutenant Jerome Ossip, asked then Staff Sergeant Caron to carry a handheld Fairchild K-20 camera. After the mission, Ossip developed photos from all the aircraft, but found that the fixed cameras failed to record anything. Film from another handheld was mishandled in developing, making Caron's the only official still photographs of the explosion. 2nd Lt. Russell Gackenback, Navigator aboard then unnamed Necessary Evil, took two still photographs of the cloud about one minute after detonation using his personal AFGA 620 camera. A handheld 16 mm film camera on The Great Artiste captured the only known motion film of the explosion. Caron's photographs of the explosion were printed on millions of leaflets that were dropped over Japan the next day.

Caron graduated from Brooklyn Technical High School (Brooklyn, New York) in 1938.In May 1995, he published the book Fire of a Thousand Suns, The George R. "Bob" Caron Story, Tail Gunner of the Enola Gay about his "eye-witness account of the momentous event when the world was catapulted into the Atomic Age, the introduction of atomic capability, the technical development of the B-29, and the events that put him into the tail gun turret of the Enola Gay."

Ivy Mike

Ivy Mike was the codename given to the first test of a full-scale thermonuclear device, in which part of the explosive yield comes from nuclear fusion. It was detonated on November 1, 1952 by the United States on the island of Elugelab in Enewetak Atoll, in the Pacific Ocean, as part of Operation Ivy. It was the first full test of the Teller–Ulam design, a staged fusion device.

Due to its physical size and fusion fuel type (cryogenic liquid deuterium), the Mike device was not suitable for use as a deliverable weapon; it was intended as an extremely conservative proof of concept experiment to validate the concepts used for multi-megaton detonations. A simplified and lightened bomb version (the EC-16) was prepared and scheduled to be tested in operation Castle Yankee, as a backup in case the non-cryogenic "Shrimp" fusion device (tested in Castle Bravo) failed to work; that test was cancelled when the Bravo device was tested successfully, making the cryogenic designs obsolete.

Long Live The Kings

Long Live The Kings is the 9th studio album released by the Kottonmouth Kings on April 20, 2010, and was the first album that featured their newest addition to the group, The Dirtball. It's also the only album to date that featured 8 members of the Kottonmouth Kings on the cover of the album, as it was released just prior to Pakelika leaving the group. The album features the likes of Tech N9ne, Insane Clown Posse, and Big B. It features the single, "At It Again", from Johnny Richter's new solo album, "Laughing", as well as a single from The Dirtball, entitled "Mushrooms", which is said to be the sequel to a song he released earlier in his career called "Mushroom Cloud".

A deluxe edition of the album including a Super Bonus CD (containing all bonus tracks that were available through other retailers' exclusives and two tracks that were only available on the Super Bonus CD) and DVD was sold exclusively through the Suburban Noize online store. The Super Bonus CD contained 16 tracks; the first 11 tracks were included on a bonus disc with the Best Buy edition of Long Live the Kings, tracks 12-14 were included as bonus tracks on the iTunes edition of the album, and tracks 15-16 were exclusive to the Super Bonus CD. The bonus CD featured guest appearances by Saint Dog and Dogboy, as well as tracks from D-Loc, DJ Bobby B, and the X-Pistols (a newly formed side group, similar to Kingspade, consisting of KMK vocalists Daddy X and The Dirtball).

MC Paul Barman

Paul Nathaniel Barman (born October 30, 1974), better known by his stage name MC Paul Barman, is an American rapper. He resides in Manhattan, New York. In 2012, LA Weekly placed him at number 14 on the "Top 20 Whitest Musicians of All Time" list.

Nuclear Energy (sculpture)

Nuclear Energy (1964–66) (LH 526) is a bronze sculpture by Henry Moore that is located on the campus of the University of Chicago at the site of the world's first nuclear reactor, Chicago Pile-1. The first human-made self-sustaining nuclear chain reaction was initiated here on December 2, 1942.

Richland High School (Washington)

Richland High School is a public secondary school in the northwest United States, located in Richland, Washington. The school was founded as Columbia High School in 1910 to serve the educational needs of the small town of Richland. The building was replaced with a much larger structure by the U.S. Army Corps of Engineers in 1946 as the development of the neighboring Hanford Engineering Works brought an infux of employees to the region to support the war effort.

Columbia High was renamed Richland High School as the small farming community continued to develop as weapons production climbed during the Cold War and the town was designated as a first class city in 1958. The facilities of were extensively renovated in 1964, and remodeled again in stages between 1995 and 2006. The school is now part of the Richland School District. Until the founding of Hanford Falcons in 1972, Richland High was the only high school in the city.Richland's mascot is the "Bomber", officially named for the Boeing B-17 Flying Fortress built in Seattle, but also in recognition of the city's contributions as an "Atomic City" in World War Two. Hanford was home to the Manhattan Project's B Reactor, the first full-scale plutonium production reactor in the world. Plutonium manufactured at the site was used in the nuclear bomb detonated over Nagasaki, Japan. Consequently, mushroom cloud logos are proudly displayed throughout the school and the student body frequently shouts "nuke 'em" at sporting events.As the region has diversified since its past as a federally owned Atomic City where 90% of the population was either employed by or a dependent of Hanford, the school has since received criticism for its depiction of a mushroom cloud as an unofficial logo for the school, believing that the logo and the mascot to be a shameful reminder of the atomic bombs dropped on Hiroshima and Nagasaki.

San Antonio, New Mexico

San Antonio is an unincorporated community and census-designated place in Socorro County, New Mexico, United States, roughly in the center of the state, on the Rio Grande. The entire population of the county is around 18,000.San Antonio is partly agricultural, and partly a bedroom community for Socorro and White Sands Missile Range.

The city supports a few small businesses, which include the original Owl Bar and Cafe (featured on an episode of the Travel Channel's Burger Land in 2013), The Buckhorn Tavern (featured in 2009 on the Food Network's Throwdown! with Bobby Flay,), San Antonio Crane, a restaurant featuring Mexican food, a seasonal roadside market, and a general store.

San Antonio is the gateway to the Bosque del Apache National Wildlife Refuge. Interstate 25 runs along the west, and U.S. Route 380 begins there and heads east to Carrizozo. The Rio Grande is just to the east of San Antonio, and the BNSF Railway runs through it and has a small yard, little more than a siding.While still part of the New Mexico Territory, the town was the birthplace of Conrad Hilton. His father was a merchant and hotelier in San Antonio, and Hilton learned the hotel trade there. Hilton was one of the original legislators in the newly formed state of New Mexico, and founded the Hilton Hotels Corporation.

San Antonio is about 28 miles from Trinity Site, where the first nuclear bomb was detonated on July 16, 1945. Residents reported tremors like an earthquake and the town received some of the remnants of the mushroom cloud, resulting in some radioactive contamination of the area, which faded quickly and does not persist today. The town was the meeting place for the scientists who detonated the bomb.

Smoke ring

A smoke ring is a visible vortex ring formed by smoke in a clear atmosphere.

Smokers may blow smoke rings from the mouth, intentionally or accidentally. Smoke rings may also be formed by sudden bursts of fire (such as lighting and immediately putting out a cigarette lighter), by shaking a smoke source (such as an incense stick) up and down, by firing certain types of artillery, or by the use of special devices, such as vortex ring toys. The head of a mushroom cloud is a large smoke ring.

A smoke ring is commonly formed when a puff of smoke is suddenly injected into clear air, especially through a narrow opening. The outer parts of the puff are slowed down by the still air (or by edges of the opening) relative to the central part, imparting it the characteristic poloidal flow pattern.

The smoke makes the ring visible, but does not significantly affect the flow. The same phenomenon occurs with any fluid, creating vortex rings which are invisible but otherwise entirely similar to smoke rings.

The Mushroom Cloud Effect

The Mushroom Cloud Effect is a street album by Pakistani hip-hop artist Adil Omar consisting of compiled tracks and previously unheard demos. It was released digitally on March 22, 2013 and features Omar's early underground work (mostly affiliated with Soul Assassins) performing on other producer's tracks as opposed to self produced material.

Thought Balloon Mushroom Cloud

Thought Balloon Mushroom Cloud is the second studio album by American hip hop musician MC Paul Barman. It was released in 2009.

White House Iraq Group

The White House Iraq Group (aka, White House Information Group or WHIG) was an arm of the White House whose purpose was to inform the public about the purpose of the 2003 invasion of Iraq.

The task force was set up in August 2002 by White House Chief of Staff Andrew Card and chaired by Karl Rove to coordinate all of the executive branch elements in the run-up to the war in Iraq. However, it is widely speculated that the intention of the task force was "escalation of rhetoric about the danger that Iraq posed to the U.S., including the introduction of the term 'mushroom cloud'" [1].


Yarraloola or Yarraloola Station is a pastoral lease that once operated as a sheep station but is currently operating as a cattle station in Western Australia.

It is located 47 kilometres (29 mi) west of Pannawonica and 80 kilometres (50 mi) east of Onslow along the Robe River in the Pilbara region.

Messrs. H. and W. Woolhouse took up Yarraloola in 1878 and had developed a good reputation for their breeding program for horses and sheep by 1886. Floodwaters following heavy rain caused severe damage to Yarraloola in 1894 with many parts of the homestead flooded under 1 foot (0.3 m) of water. A total of 400 sheep were washed away in the floodwaters as was about 10 miles (16 km) of fencing. By the end of the same year 10,500 sheep were shorn for a clip of 150 bales of wool.The property was put up for auction in 1898, at this time it occupied an area of 295,400 acres (119,544 ha) and had 25 miles (40 km) of double frontage on the Robe River. The area was grassed with silver, plain and bundle-bundle grasses as well as areas of salt bush. Two three room cottages made from jarrah with iron roofing, a corrugated iron woolshed, yards, sleeping quarters, kitchen and blacksmith shop had been built along with seven paddocks contained within 80 miles (129 km) of fencing. Stocked with 11,600 mixed sheep, 230 cattle and 180 horses watered by the river and seven windlasses it was acquired by G.P Paterson and A.R. Richardson, who had previously partly owned Yeeda Station.In 1915, the property passed 16,500 sheep over the boards during shearing producing 250 bales of wool. This followed an excellent season where the 17.5 inches (444 mm) was recorded in six months. Although the 1919 season was poorer with Yarraloola only receiving 1.59 inches (40 mm) over seven months, 19,500 sheep were shorn yielding 252 bales of wool.The current homestead was constructed by Keith Paterson in 1919, the building process was quite slow but improved as road access to the station for motor vehicles arrived in the 1920s.Station workers felt the tremor and saw the mushroom cloud produced by a nuclear test conducted on the Monte Bello Islands in 1952, situated approximately 80 miles (129 km) from the property.The station was severely flooded in 2009 when the Robe River burst its banks. Jason Reimers, the station manager, and his family had to be evacuated from the property after a tropical depression crossed the coast.Yarraloola is currently owned by Robe River Iron Associates joint venture through the Yarraloola Pastoral Company and managed by Rio Tinto.


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