Emma Wilson
Mushroom clouds are formed by large explosions, most notably nuclear detonations. They are characterised by their distinctive shape, which includes a stem and a head. The height of mushroom clouds can vary, but they can reach impressive altitudes. For example, the mushroom cloud produced by the atomic bombing of Hiroshima rose to over 60,000 feet in about ten minutes. The total height of a mushroom cloud can be influenced by various factors, including the type of weapon, burst altitude, and weather conditions.
| Characteristics | Values |
|---|---|
| Formation | Mushroom clouds are formed by large explosions under Earth's gravity, and are best known for their appearance after nuclear detonations. |
| Height | The height of a mushroom cloud can vary, but they can reach extremely high altitudes. For example, the mushroom cloud over Hiroshima rose to over 60,000 feet in about ten minutes. Another source states the total height of a mushroom cloud is 2,872.932 meters. |
| Composition | The heads of mushroom clouds consist of highly radioactive particles, primarily fission products and weapon debris aerosols. These particles remain suspended in the air even after the cloud disappears due to the evaporation of condensed water. |
| Fallout | Mushroom clouds can cause nuclear fallout, especially in the presence of rain. The fallout may appear as dry, ash-like flakes, or as invisible particles. The largest and most radioactive particles are deposited in the first few hours after the blast, while smaller particles can reach the stratosphere and stay there for extended periods. |
| Accompanying Phenomena | Mushroom clouds are often accompanied by short-lived vapour clouds known as "Wilson clouds" or condensation clouds. These are caused by a sudden rarefaction of the surrounding medium, leading to a drop in temperature and the condensation of moisture. |
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What You'll Learn
- The tallest mushroom cloud on record was over Hiroshima, reaching 60,000 ft in 10 minutes
- Mushroom clouds are formed by large explosions, most notably nuclear detonations
- The height of a mushroom cloud is determined by when it reaches equal density with the air
- The mushroom head contains highly radioactive particles, which can cause beta burns
- The vapour clouds that accompany mushroom clouds are known as Wilson clouds
The tallest mushroom cloud on record was over Hiroshima, reaching 60,000 ft in 10 minutes
Mushroom clouds are formed by large explosions, but they are most commonly associated with the aftermath of nuclear detonations. The distribution of radiation in a mushroom cloud varies with the type of weapon, the burst altitude, the terrain, and the weather, among other factors. The heads of the clouds consist of highly radioactive particles, which are usually dispersed by the wind.
Nuclear mushroom clouds are often accompanied by short-lived vapour clouds, known as "Wilson clouds" or "condensation clouds". These are caused by a sudden rarefaction of the surrounding medium, leading to a drop in temperature and the condensation of moisture in the air.
The tallest mushroom cloud on record was over Hiroshima, reaching 60,000 feet in about ten minutes. The atomic bomb, known as "Little Boy", was dropped on the city of Hiroshima on August 6, 1945, at 8:16 a.m. The cloud was visible from the Enola Gay plane, which was flying at 30,000 feet, just 30 seconds after the explosion. The city was engulfed in a thick black smoke, with numerous fires started by the heat of the bomb and the knocking over of charcoal stoves used for cooking.
A rare photograph of the mushroom cloud was discovered in a former Japanese elementary school, providing a glimpse of the bomb's immediate aftermath. The image shows the distinct two-tiered cloud as it was seen from Kaitaichi, six miles east of Hiroshima's centre. According to experts, the towering plume seen in the photograph is not the original mushroom cloud, which would have dissipated within hours of the strike.
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Mushroom clouds are formed by large explosions, most notably nuclear detonations
Under the Earth's gravity, the by-products of a large explosion produce a unique cloud formation. When a nuclear weapon is detonated above the ground, a fireball forms and begins to rise, acting similarly to a hot-air balloon. This rising fireball creates a Rayleigh-Taylor instability, drawing air upwards and generating strong air currents known as "afterwinds". The explosion also lifts a significant amount of moisture-laden air from lower altitudes.
As the warm, moist air ascends, it cools down, causing the water vapour to condense into water droplets and eventually freeze into ice crystals. This phase change releases latent heat, further propelling the cloud to higher altitudes. The heads of mushroom clouds contain highly radioactive particles, primarily fission products and weapon debris aerosols. These radioactive particles can remain suspended in the air even after the cloud becomes invisible as the water droplets evaporate.
The height of a mushroom cloud can vary depending on the explosion's yield and other factors. For example, the mushroom cloud over Hiroshima, Japan, following the atomic bomb attack in 1945, rose to over 60,000 feet in approximately ten minutes. Another source mentions a mushroom cloud with a total height of 2,872.932 meters.
The distribution of radiation within the mushroom cloud is influenced by factors such as explosion yield, weapon type, fusion-fission ratio, burst altitude, terrain type, and weather conditions. Lower-yield explosions tend to have a higher proportion of their radioactivity in the mushroom head, while megaton-range explosions have more radioactivity in the lower third of the cloud. The fallout from these explosions can take on various forms, from dry, ash-like flakes to invisible particles deposited by rain.
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The height of a mushroom cloud is determined by when it reaches equal density with the air
Mushroom clouds are the result of large explosions, most notably nuclear detonations. The height of a mushroom cloud is influenced by various factors, including the energy of the explosion, the atmospheric conditions, and the density of the surrounding air.
The formation of a mushroom cloud begins with the rapid expansion of lower-density gases at any altitude. This creates a Rayleigh-Taylor instability, leading to the formation of turbulent vortices that curl downward, forming a temporary vortex ring. This upward motion draws in a central column of smoke, debris, condensed water vapour, or a combination of these elements, forming the iconic mushroom stem.
As the buoyant mass of gas rises, it eventually reaches an altitude where it is no longer less dense than the surrounding air. At this point, the cloud stabilizes and begins to disperse, marking the maximum height attained by the mushroom cloud. The height at which stabilization occurs depends on factors such as temperature profiles, dew point, and wind shear in the atmosphere.
The height of a mushroom cloud can vary significantly. For instance, the atomic bomb explosion over Nagasaki, Japan, produced a mushroom cloud that reached a height of 45,000 feet, as described by an eyewitness account published in The New York Times in 1945. On the other hand, the typical height at which mushroom clouds stabilize is around 6-8 miles above the Earth's surface, which is known as the tropopause. Once the cloud reaches this altitude, it tends to spread out laterally, contributing to the characteristic mushroom shape.
The height at which a mushroom cloud stabilizes is indeed determined by when it reaches equal density with the surrounding air. This occurs when the upward motion of the cloud slows as it ascends and cools, eventually reaching an altitude where its density matches that of the ambient air. At this point, the cloud can no longer rise and begins to disperse, marking the maximum height of the mushroom cloud.
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The mushroom head contains highly radioactive particles, which can cause beta burns
Mushroom clouds are formed by large explosions under Earth's gravity, but they are most commonly associated with the aftermath of nuclear detonations. The size of the explosion determines the distribution of radiation in the mushroom cloud. Lower-yield explosions have about 90% of their radioactivity in the mushroom head, or cloud, and 10% in the stem. Conversely, megaton-range explosions tend to have most of their radioactivity in the lower third of the mushroom cloud.
The mushroom head contains highly radioactive particles, primarily fission products, and other weapon debris aerosols. These particles are usually dispersed by the wind, but weather patterns, especially rain, can produce nuclear fallout. The fallout may appear as dry, ash-like flakes, or as particles too small to be visible, which are often deposited by rain.
The radioactive particles can be carried for considerable distances. For instance, radiation from the Trinity test was washed out by a rainstorm in Illinois, and unanticipated winds carried lethal doses of Castle Bravo fallout over the Rongelap Atoll, necessitating its evacuation.
Large amounts of newer, more radioactive particles deposited on the skin can cause beta burns, which often manifest as discoloured spots and lesions on the backs of exposed animals. Beta burns are shallow surface burns, usually affecting the skin, and less frequently the lungs or gastrointestinal tract. They are caused by beta particles, typically from hot particles or dissolved radionuclides that come into direct contact with or close proximity to the body. Beta burns can appear similar to sunburn, but unlike gamma rays, beta emissions are stopped much more effectively by materials. Therefore, they deposit all their energy in only a shallow layer of tissue, causing more intense but more localized damage.
The symptoms of beta burns include itching and/or a burning sensation that lasts for one or two days, sometimes accompanied by hyperaemia. After 1-3 weeks, burn symptoms such as erythema, increased skin pigmentation, epilation, and skin lesions may appear.
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The vapour clouds that accompany mushroom clouds are known as Wilson clouds
Mushroom clouds are distinctive mushroom-shaped clouds of debris, smoke, and condensed water vapour that form after large explosions. They are most commonly associated with nuclear explosions, but any sufficiently energetic detonation or deflagration can produce a similar effect.
Nuclear mushroom clouds are often accompanied by short-lived vapour clouds known as Wilson clouds, condensation clouds, or vapour rings. These clouds are formed by the "negative phase" following the positive overpressure behind a shock front, which causes a sudden rarefaction of the surrounding medium. This low-pressure region leads to 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.
The term "Wilson cloud" is derived from the Wilson cloud chamber, a particle detector invented by Scottish physicist Charles Thomson Rees Wilson in the early 20th century. The chamber uses condensation from a rapid pressure drop to track the paths of electrically charged subatomic particles. The Wilson cloud was so named due to its visual similarity to the clouds formed in Wilson's chamber.
Wilson clouds are distinct from the larger, more persistent structures that form later, such as the "cauliflower cloud" and the base surge, which are composed of water, spray, and radioactive particles from the explosion. The primary mushroom cloud from an air burst is formed by the rising column of hot, compressed gas and bomb debris, rather than being primarily a condensation phenomenon like the Wilson cloud.
The shape and appearance of Wilson clouds are influenced by the speed, temperature, and humidity of different atmospheric layers. During nuclear tests, condensation rings around or above the fireball are commonly observed. These rings can become stable and form rings around the rising stem of the mushroom cloud. The lifetime of a Wilson cloud during a nuclear air burst can be shortened by the thermal radiation from the fireball, which causes the cloud to heat up and evaporate.
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Frequently asked questions
The height of mushroom clouds can vary. The mushroom cloud over Hiroshima rose to over 60,000 feet in about ten minutes. Another source states that the total height of a mushroom cloud is 2,872.932 meters.
Mushroom clouds are formed by large explosions under Earth's gravity. They are most commonly associated with nuclear detonations, where the blast is detonated above the ground to maximize the effect of the blast wave and fireball.
After the detonation, the fireball rises, creating a "spherical cap bubble". As it rises, a Rayleigh-Taylor instability is formed, and air is drawn upwards, creating strong air currents known as "afterwinds". The phase change releases latent heat, causing the cloud to rise higher.
Mushroom clouds from nuclear explosions carry radioactive particles that remain suspended in the air, causing nuclear fallout. The fallout may appear as dry, ash-like flakes or invisible particles deposited by rain. These particles can cause beta burns on the skin of exposed individuals or animals.
