For an explosion to occur, there must be a rapid, forceful expansion of matter. There are numerous ways this can happen, both naturally and artificially, such as
volcanic eruptions, or two objects striking each other at very high speeds, as in an
impact event. Explosive volcanic eruptions occur when
magma rises from below, it has dissolved gas in it. The reduction of
pressure as the magma rises causes the gas to bubble out of solution, resulting in a rapid increase in volume, however the size of the magma chamber remains the same. This results in pressure buildup that eventually leads to an explosive eruption. Explosions can also occur outside of Earth in the universe in events such as
supernovae, or, more commonly, stellar flares. Humans are also able to create explosions through the use of
explosives, or through
nuclear fission or
fusion, as in a
nuclear weapon. Explosions frequently occur during
bushfires in
eucalyptus forests where the volatile oils in the tree tops suddenly combust.
Astronomical around
Wolf–Rayet star WR 124 is the remnants of a
stellar explosion, which is currently observed as six
light years across Among the largest known explosions in the universe are
supernovae, which occur after the end of life of some types of
stars.
Solar flares are an example of common, much less energetic, explosions 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 meteoroid or an asteroid impacts the surface of another object, or
explodes in its atmosphere, such as a planet. This occurs because the two objects are moving at very high speed relative to each other (a minimum of for an Earth impacting body). For example, the
Tunguska event 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
gravitational waves. This is capable of transmitting ordinary energy and destructive forces to nearby objects, but in the vastness of space, nearby objects are 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 nine solar masses in the form of gravitational energy.
Chemical is an example of a chemical explosive. The most common artificial explosives are chemical explosives, usually involving a rapid and violent
oxidation 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'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. Chemical reactions that cause explosions can are typically either unimolecular decomposition reactions or multi-molecular reduction-oxidation (redox) reactions.
Electrical and magnetic that has exploded A high current electrical fault can create an "electrical explosion" by forming a high-energy
electrical arc which rapidly vaporizes metal and insulation material. This
arc flash hazard is a danger to people working on energized
switchgear. Excessive
magnetic pressure within an ultra-strong
electromagnet 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 explosions, a
nuclear weapon 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==