Land Mine
A land mine is a hidden explosive device that is buried in the ground. There are basic one-stage mines that explode on contact, and two-stage models that fly into the air before shattering into deadly shrapnel. A few types illuminate the battlefield instead, either by burning where detonated or firing a flare into the sky.
Although land mines are a relatively recent invention, the use of underground explosives dates back hundreds of years. Besieging armies would try to capture fortified cities by putting primitive mines beneath their walls. During the American Civil War, devices called land torpedoes were used occasionally, despite universal condemnation of such "infernal devices." They were usually 24-pound artillery shells fitted with a sensitive percussion fuse.
The Germans developed the first true land mines during World War I, and used them to disable Allied armored vehicle s. Each mine was an artillery shell buried with the fuse facing up; when a tank ran over it, the mine exploded. During the next World War, land mines became more sophisticated, and were used for specific purposes. One antitank mine, the German Teller mine, was encased in steel and could hold 12 pounds (5.4 kg) of TNT. It also featured an antilifting device, a fuse on the bottom that went off if the mine was unearthed. Antipersonnel mines, such as the Spreng or S-mine, were also created by the Germans. These resembled large tin cans. A trip wire projected from their tops and was attached to a nearby stick driven into the ground. If the wire was touched, a propellant fired the mine out of the ground. When it reached waist height, the anchor wire triggered the main charge (usually less than one pound of TNT), sending steel balls and shrapnel over a wide area.
As lethal as they were, steel mines had one weakness: they could be located with a metal detector. Today's land mines are housed in plastic, which makes finding them more difficult. They are also more brutally efficient. An English design called the bar mine has a rectangular pressure plate that rests above a much longer, bar-shaped charge. If a tank touches even the edge of the plate the charge detonates and its oblong form creates a wider explosion that ensures maximum damage. Other mines use a shaped charge to propel a high-speed jet of burning gases or to target their fragments in a specific direction. Chemical mines disperse a nonexplosive but equally deadly payload. They are especially effective when sown among conventional mines, because the explosives slow advancing troops and increase exposure to the chemical.
Some mines are designed to deactivate themselves after a set time, but these so-called ÒsmartÓ mines are the exception, and most mines can remain active and lethal for over ten years. By 1997, it was estimated that more than 100 million mines lay scattered in over 60 countries, many in regions disturbed by civil wars. The threat of land mines continued in many areas long after the war itself was resolved. Groups in countries around the world began working to ban antipersonnel land mines in the late 1990s. The anti-land mine crusade gained momentum with the support of Diana, Princess of Wales, shortly before her death in 1997, and with the awarding of the 1997 Nobel Peace Prize to an American anti-land mine group. In December1997, an international treaty banning land mines was signed in Ottawa, though the United States, a major land mine user, refused to sign.
While civilian protests against the use of land mines gained a victory with the signing of the treaty, land mine removal technology also advanced. Since plastic mines cannot be located with metal detectors, new methods were needed to detect them. The United States Department of Defense began researching alternate technology in 1995, and developed several methods for finding plastic mines. One of the most successful was an infrared detector that senses thermal anomalies surrounding mines. The Department of Defense also investigated sensors using ground penetrating radar, acoustic and microwave sensors, and sensors that can locate TNT by scent (as specially trained mine-detecting dogs do). A possibility for a future mine-removal system might be to genetically engineer fruit flies to locate TNT.
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