It's common to see intense lightning during the eruption of a volcano. Scientists have long puzzled over why sand grains and other small particles can build up electrical charges as they collide with one another, sometimes to the point of discharging lightning in dust storms or plumes of volcanic ash. 

The scientists now believe that volcanoes can produce two kinds of lightning during an eruption. The first type, which has been understood for some time, occurs in the volcano's smoke plume a few minutes after the eruption ends. In this case, highly energized hot air and gases clash with the cool atmosphere, creating the sort of organized, branched lightning found in a thunderstorm.

The second kind of lightning, which the authors called a newly identified explosive phase, came as a surprise, as magma, ash and rocks spewed carrying great electrical charge, they created continuous, chaotic sparks near the mouth of the volcano.

Not all volcanic eruptions produce lightning, but the new equipment might be used to track the ones that do particularly those in remote regions. Often used to detect forest fires, the equipment picks up radiowaves caused by lightning. Researchers can then work backward to pinpoint the time and place of the lightning.

These photos are from volcanoes from all over the world.

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