【Belgium】

After sleeping for over 40 years,Belgium the Philippines' Taal volcano awoke over the weekend, blasting a plume of ash at least 32,000 feet into the sky.

And in this ominous plume, thunder clapped and lightning streaked through the dark column of volcanic ash.

The profoundly dangerous Taal — with over 24 million peopleliving within 60 miles of the volcano — produced a scintillating, at times mesmerizing, light show. (Taal's activity also prompted a mass evacuationof almost 1 million people should there be a bigger eruption.)

Volcanic lightning, however captivating, is common, explained Sonja Behnke, a scientist at Los Alamos National Laboratory who researches these volcanic phenomena and has repeatedly observed volcanic lightning in places like Iceland and Japan.

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How volcanic lightning happens

There are two major steps.

1. First, the volcanic ash needs an electric charge. When a volcano erupts explosively (as opposed to gentler lava eruptions from, for example, Hawaiian volcanoes), it ejects exploded particles of molten rock (aka "magma") into the air, which becomes volcanic ash. In the towering plume of ash, these billions of particles start colliding and rubbing against each other, which creates charged volcanic particles. It's similar to how you create static electricity by rubbing socks on carpet. "The ash gets charged as the volcano is erupting," said Behnke.

"It’s essentially the same reason we get lightning and thunder in storm clouds," added atmospheric scientist Adam Varble, who researches thunderstorms at Pacific Northwest National Laboratory. "It's the collision of particles." But in storm clouds, instead of ash particles rubbing together, it's only ice particles colliding together to create electric charges.

2. Then, to get bolts of lightning, the charged particles need to separate into different regions of a volcano's ash plume. In the chaotic plume, this happens naturally as differently sized ash particles fall down at different speeds, creating different zones of charged particles, either positive or negative. (What gives one region of particles a positive or negative charge is "complicated physics" that's still being investigated, explained Varble.)

But the important point is when you have two regions of oppositely charged particles, the space between becomes an electric field, which allows electricity to shoot or flow through the air. These are the bolts of lightning you see streaking through storm clouds or volcanic plumes.

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These radiant bolts of lightning, whether in volcanic plumes or thunderstorms, are powerful, creating between 10 million volts to billions of volts, explained Varble. (Toasters usually operate at between 120 to 220 volts.)

Taal certainly created lots of lightning. That's likely because the plume reached so high into the freezing atmosphere that water ejected during the eruption turned into little ice particles, which also started colliding and creating static electricity, explained Behnke. This means there was a double whammy of both ash and ice creating charged particles.

There may have been a lot of water in Taal's ashy plume, because a lake sat on top of the volcano, meaning the eruption blew through a lake.

"It seems like volcanoes that have a good interaction with water when erupting get more dramatic displays of lighting," said Behnke.

For volcano scientists, volcanic lightning is more than just a natural spectacle. The U.S. Geological Survey now uses lightning to track volcanic eruptions as they happen, said Behnke.

Many eruptions happen in remote places and aren't directly observed by people. But lightning is detectable from satellites, which gives scientists' better insight into the planet's constantly erupting volcanoes.

"It's very common during explosive ash-producing eruptions," Alexa Van Eaton, a USGS volcanologist, tweeted. "So common, in fact, that we use it to help monitor volcanism around the world."