column. The base surge billows upward to a height ofseveral hundred feet and expands rapidly outward to adistance of several thousand yards. Then it graduallyrises from the surface and merges with the cloud formedby the escaping fireball.EFFECTS OF NUCLEAR WEAPONSDetonation of the nuclear bomb creates a blast wavethat travels outward in all directions at an initial speedmuch greater than the speed of sound. When the wavestrikes the earth’s surface, another wave is formed byreflection. At some distance from ground zero(depending on the height of the blast), the primary andreflected waves combine to form a reinforced blastwave. Pressure at the wave front, called overpressure, ismany times that of normal atmospheric pressure and iswhat causes most of the physical damage. Additionally,underwater bursts create large water waves, some ofwhich reach heights of over 90 feet within a fewhundred feet from the blast. The water waves traveloutward at high speed for a distance of several miles,gradually diminishing in size. The overpressuredecreases as the distance from the blast increases, but itcan cause damage many miles from the blast.Nuclear weapons produce explosions of great forceand heat and release nuclear radiation. Their primarypurpose is the mass destruction of property andpersonnel. Their effects are divided into threecategories—blast waves or shock waves, incendiary,and radiation.Blast Waves or Shock WavesInjuries caused by blast waves can be divided intoprimary (direct) injuries and secondary (indirect)injuries.PRIMARY BLAST INJURIES.—Primary blastinjuries result from the direct action of the air shockwave on the human body. The greater the weapon’s size,the greater the blast wave’s effective range, with asubsequent increase in casualties.SECONDARY BLAST INJURIES.—Secondaryblast injuries are caused by strong blast winds reachinghundreds of miles per hour collapsing buildings andtimber and flinging debris about. Personnel may also behurled against stationary objects or thrown to theground by high winds accompanying the explosion.At sea, the shock wave accompanying anunderwater burst produces various secondary injuries.Causalities resemble those caused by moreconventional underwater weapons, such as mines anddepth charges. Instead of being localized, the casualtiesextend over the entire ship. Also, injuries result frompersonnel being thrown against fixed objects orstructures. Unsecured objects can act as missiles andcause many injuries.IncendiaryThere are two general ways fires can originate in anuclear explosion.1. First, kindling fuels can be ignited as a directresult of the absorption of thermal radiation.2. Second, fires can be started from electrical shortcircuits, broken gas lines, or other interruptedheat sources as an indirect effect of the blastwave.13-10Student Notes:Figure 13-4.—A subsurface burst.
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