• Volcanic lightning has very little to do with tectonic activity, and everything to do with everyday physics.
     
    Volcanic lightning is not formed deep in the Earth. It only forms in a volcanic plume, the cylinder-shaped column of volcanic ash emitted by some erupting volcanoes. Volcanoes that lack a thick volcanic plume usually lack volcanic lightning. Volcanoes in Hawaii, for instance, are more likely to eject fluid lava fountains than thick plumes of ash. These volcanoes rarely have volcanic lightning.
     
    The tiny particles that make up a volcanic plume are tightly compressed beneath a volcano. The airy atmosphere aboveground, however, is much less dense. This change in density contributes to volcanic lightning.
     
    As densely packed particles are violently ejected in a volcanic plume, they rub against each other. This interaction is called friction. Through friction, ash particles gain and lose electrons—they become electrically charged. As charged particles ascend the less-dense volcanic plume, the plume experiences charge separation. Positively charged particles become increasingly separated from negatively charged particles.
     
    When the charge separation becomes too great for air to resist the flow of electricity, lightning tears through the volcanic plume to connect the positively and negatively charged particles.
     
    Everyday Lightning
     
    You don’t need an actual volcano to get an idea of how volcanic lightning works. Friction creates charged particles when you rub a balloon across your hair or your socked feet across a carpet. You’re covering the balloon or yourself with negative particles. This imbalance of electrons is called static electricity.
     
    Eventually, you come into contact with something—another person or a metal doorknob, for instance—that is not electrically charged. The static “shock” you receive is the lightning-fast discharge of electrons.

    1. Volcanic lightning is most often reported at night. Why do you think people are more likely to report seeing volcanic lightning at night than during the day?

      Show Answer

      Volcanic lightning is most likely to appear at the beginning of an eruption, no matter what time of day that happens.

      People are more likely to see volcanic lightning at night, however. Volcanic lightning may crackle during daytime eruptions, but is more likely to be lost in the sun’s glare.

    2. Lightning from thunderclouds can appear as bolts, sheets, or balls. What shapes do you think volcanic lightning can take?

      Show Answer

      All of the above! During the 1980 eruption of Mount St. Helens, Washington, for instance, the thick volcanic plume produced bolts of lightning connecting to the ground, sheet lightning connecting in the plume itself, and ball lightning bouncing near the volcano.

    3. A common nickname for the conditions that support volcanic lightning is a “dirty thunderstorm.” What makes this thunderstorm “dirty”?

      Show Answer

      The “dirt” is the thick ash and rock of the volcanic plume.

  • Articles & Profiles

    Images

  • Term Part of Speech Definition Encyclopedic Entry
    ascend Verb

    to go up.
    atmosphere Noun

    layers of gases surrounding a planet or other celestial body.

    		 Encyclopedic Entry: atmosphere
    charge separation Noun

    building of space between charged particles. Sometimes called static electricity.
    compress Verb

    to press together in a smaller space.
    cylinder Noun

    tube or long, circular object.
    dense Adjective

    having parts or molecules that are packed closely together.
    discharge Verb

    to eject or get rid of.
    eject Verb

    to get rid of or throw out.
    electricity Noun

    set of physical phenomena associated with the presence and flow of electric charge.
    electron Noun

    negatively charged subatomic particle.
    emit Verb

    to give off or send out.
    erupt Verb

    to explode or suddenly eject material.
    fluid Noun

    material that is able to flow and change shape.
    friction Noun

    force produced by rubbing one thing against another.
    lava fountain Noun

    phenomenon where lava is forcefully but not violently ejected from a volcano through a fissure or vent.
    particle Noun

    small piece of material.
    physics Noun

    study of the physical processes of the universe, especially the interaction of matter and energy.
    static electricity Noun

    motionless electronic charge that builds up on a material.
    tectonic activity Noun

    movement of tectonic plates resulting in geologic activity such as volcanic eruptions and earthquakes.
    violent Noun

    strong, destructive force.
    volcanic ash Noun

    fragments of lava less than 2 millimeters across.

    		 Encyclopedic Entry: volcanic ash
    volcanic lightning Noun

    bolts of electricity produced in a volcanic plume. Also called a dirty thunderstorm.
    volcanic plume Noun

    cylinder-shaped structure of volcanic ash and gas emitted by an explosive volcanic eruption. Also called an eruption column.
    volcano Noun

    an opening in the Earth's crust, through which lava, ash, and gases erupt, and also the cone built by eruptions.

    		 Encyclopedic Entry: volcano
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Writer

Caryl-Sue, National Geographic Society

Editor

Melissa MacPhee, National Geographic Society

Producer

Caryl-Sue, National Geographic Society

Last Updated

Oct. 28, 2015

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