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Lightning Injuries
This page focuses on understanding the pathophysiology, assessment, and treatment of lightning injuries. The material on this page is summarized for field use in the Environmental section of the Wilderness Medicine Handbook.
Contents
Contents
The Physics of Lightning
Thunderstorms and lightning are created when water molecules within the rising warm air become ionized (negatively charged) as they enter the cooler air in the upper atmosphere. Between 5 and 10 kilometers negatively charged water vapor condenses and turns to water droplets and ice crystals. When heavy enough to overcome the updraft, the droplets or crystals fall as rain or hail, bringing the cooler air and their negative charges with them. As negative charges accumulate at the bottom of the cloud, a step leader shoots at 150-foot (45.7-meter) intervals toward the ground. Because like charges repel one another, the negative charges at the bottom of the cloud force the electrons in all objects below the cloud deep into the ground, leaving positive charges to accumulate directly below the cloud. As the positive charges increase in strength, they create electron streams known as "dart leaders," which move upward towards the cloud and connect with the negative step leader moving down to complete the circuit. This initial upward stroke is followed by a massive return stroke.
Thunder is the result of super-heated air abruptly expanding outward from the completed circuit. The process continues until the charges are equalized. A single lightning bolt is really a series of sequential strokes one immediately after the other. The multiple strokes are responsible for the characteristic flickering and branching.
Thunder is the result of super-heated air abruptly expanding outward from the completed circuit. The process continues until the charges are equalized. A single lightning bolt is really a series of sequential strokes one immediately after the other. The multiple strokes are responsible for the characteristic flickering and branching.
There are three basic lightning scenarios:
- Mountainous regions with cool nights and hot days. Mountain storms tend to develop during the hottest part of the summer. Falling cool air from the high mountains feeds developing storms as it dives under the warm air at lower elevations pushing it upward. Local lakes increase the moisture content of the system and the severity of the storms.
- A cold front moving in under an existing warm air mass forces warm air upward causing lines of thunder storms to form behind it.
- Dark land masses surrounded (or partially surrounded) by cooler water. Water retains its relative coolness from the winter due to its tremendous mass. The darker land heats up in the hot summer sun and heats the air close to the ground causing it to rise and form thunderstorms.