Definitions

Volcanic bomb

smart bomb

Bomb with a guidance system that directs its path toward a target. It is steered by fins or wings on the bomb that move in response to guidance commands. Guidance systems may be electro-optical, laser, infrared, or inertial. Electro-optical systems send pictures of the area so that the bomb can be guided onto the target. Laser-guided bombs follow the reflections of a laser beam trained onto the target by an aircraft or a spotter on the ground. Infrared guidance responds to radiation generated by warm areas of the target. Inertial navigation is based on inputting coordinates derived from radar systems or from Global Positioning System satellites into the bomb's gyroscopes. Smart bombs, initially used in the Vietnam War, offer far greater accuracy than traditional gravity, or “dumb,” bombs.

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or enhanced radiation warhead

Small thermonuclear weapon that produces minimal blast and heat but releases large amounts of lethal radiation. The blast and heat are confined to a radius of only a few hundred yards; within a somewhat larger area, the bomb throws off a massive wave of neutron and gamma radiation, which is extremely destructive to living tissue. Such a bomb could be used with deadly efficiency against tank and infantry formations on the battlefield without endangering towns or cities only a few miles away. It can be carried in a missile or delivered by a howitzer or even an attack aircraft.

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or H-bomb or thermonuclear bomb

Weapon whose enormous explosive power is generated by the nuclear fusion of hydrogen isotopes. The high temperatures required for the fusion reaction are produced by detonating an atomic bomb (which draws its energy from nuclear fission). The bomb's explosion produces a blast that can destroy structures within a radius of several miles, an intense white light that can cause blindness, and heat fierce enough to set off firestorms. It also creates radioactive fallout that can poison living creatures and contaminate air, water, and soil. Hydrogen bombs, which may be thousands of times more powerful than atomic bombs, can be made small enough to fit in the warhead of a ballistic missile (see ICBM) or even in an artillery shell (see neutron bomb). Edward Teller and other U.S. scientists developed the first H-bomb and tested it at Enewetak atoll (Nov. 1, 1952). The Soviet Union first tested an H-bomb in 1953, followed by Britain (1957), China (1967), and France (1968). Most modern nuclear weapons employ both fusion and fission.

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In volcanology, any unconsolidated volcanic material that has a diameter greater than 1.25 in. (32 mm). Bombs form from clots of wholly or partly liquid lava ejected during a volcanic explosion; they solidify and become rounded during flight. The final shape is determined by the initial size, viscosity, and flight velocity of the magma.

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First atomic bomb test, near Alamogordo, New Mexico, July 16, 1945.

Weapon whose great explosive power results from the sudden release of energy upon the splitting, or fission, of the nuclei of heavy elements such as plutonium or uranium (see nuclear fission). With only 11–33 lb (5–15 kg) of highly enriched uranium, a modern atomic bomb could generate a 15-kiloton explosion, creating a huge fireball, a large shock wave, and lethal radioactive fallout. The first atomic bomb, developed by the Manhattan Project during World War II, was set off on July 16, 1945, in the New Mexico desert. The only atomic bombs used in war were dropped by the U.S. on Hiroshima on Aug. 6, 1945, and on Nagasaki three days later. In 1949 the Soviet Union tested its first atomic bomb, followed by Britain (1952), France (1960), China (1964), India (1974), and Pakistan (1998). Israel and South Africa were suspected of testing atomic weapons in 1979. Seealso hydrogen bomb; Nuclear Non-proliferation Treaty; nuclear weapon.

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A volcanic bomb is a globe of molten rock (tephra) larger than 65 mm (2.5 inches) in diameter, formed when a volcano ejects viscous fragments of lava during an eruption. They cool into solid fragments before they reach the ground. Lava bombs can be thrown many kilometres from an erupting vent, and often acquire aerodynamic shapes during their flight. Bombs can be extremely large; the 1935 eruption of Asama in Japan expelled bombs measuring 5-6 m in diameter up to distances of 600 m from the vent.

Volcanic bombs are a significant volcanic hazard, and can cause severe injuries and death to people in an eruption zone. One such incident occurred at Galeras volcano in Colombia in 1993; six people near the summit were killed and several seriously injured by lava bombs when the volcano erupted unexpectedly.

Types of Bombs

Bombs are named according to their shape, which is determined by the fluidity of the magma from which they are formed.

1. Ribbon or cylindrical bombs

These bombs form from highly to moderately fluid magma, ejected as irregular strings and blobs. The strings break up into small segments which fall to the ground intact and look like ribbons. Hence, the name- ribbon bombs. These bombs are circular or flattened in cross section, are fluted along their length, and have tabular vesicles.

2. Spherical bombs

These bombs also form from high to moderately fluid magma. In the case of spherical bombs, surface tension plays a major role in pulling the ejecta into spheres.

3. Spindle, fusiform, or almond/rotational bombs

These bombs are formed by the same processes as spherical bombs, though the major difference being the partial nature of the spherical shape. Spinning during flight leaves these bombs looking elongated or almond shape, the spinning theory behind these bombs' development has also given them the name 'fusiform bombs'. Spindle bombs are characterised by longitudinal fluting, one side slightly smoother and broader than the other. This smooth side represents the underside of the bomb as it fell through the air.

4. Cow-dung bombs

These are formed when highly fluid magma falls from moderate height (so the bomb does not solidify before impact) which are still liquid when they strike the ground. They consequently flatten or splash and form irregular roundish disks which resemble cow-dung.

5. Bread-crust bombs

If the outside of a lava bomb solidifies during its flight, it may develop a cracked outer surface as the interior continues to expand. This type of lava bomb is known as a bread-crust bomb.

6. Cored bombs

Cored bombs are bombs that have rinds of lava enclosing a core of previously consolidated lava. The core consists of accessory fragments of an earlier eruption, accidental fragments of country rock or in rare cases bits of lava formed earlier during the same eruption.

External links

  • http://www.gc.maricopa.edu/earthsci/imagearchive/bombs.htm
  • http://volcanoes.usgs.gov/Products/Pglossary/bomb.html

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