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Understanding Lightning: Ground Current

When lightning strikes the ground or an object on the ground, the discharge occurs in and along the ground surface (not deep into the ground). This creates a dangerous and potentially deadly ground current near the lightning strike.

Ground current is responsible for killing many farm animals on a yearly basis. The threat of a fatal incident is affected by the distance between contact points with the ground and also the orientation of those contact points with respect to the lightning strike and discharge path. Farm animals have a long span between their front and back legs making them more vulnerable to ground current from a nearby lightning strike.

In humans, the risk of a lightning death or injury increases for a person lying on the ground because the greatest distance between contact points (usually between the head and feet) is greater than the distance of the contact points (2 feet) if the person was standing up. In the U.S., many lightning deaths and injuries are related to ground current.

ground current bridge, see text for description
golfer and ground current
20 cows laying under tree after being killed by lightning


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