What cause electrical storms to form above volcanoes?

Asked by sferik (6121

) December 24th, 2008

Looking at the photographs of the year, I was struck by the first one of a ball of lightning above the Chaiten volcano. The caption states: “Cases of electrical storms breaking out directly above erupting volcanoes are well documented, although scientists differ on what causes them.”

So what are the different theories? I’ve never seen or heard of this amazing phenomenon before. I must know more.

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7 Answers

I had heard that it was caused by static build-up from the friction of ash particles.

Edit:
Just found these three hypotheses:

A. the interactions between ash particles causing a static buildup
B. ash acting as condensation nucleii for magmatic water which then accretes as ice via riming. Charging then occurs as in a thunderstorm
C. a piezoelectrical source due to the fracture of crystals upon eruption

source

Harp (19179

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Harp hit it on the head. This is called a “dirty thunderstorm,” and is generated from friction in the ash, in the same way that regular thunder is generated from friction between ice crystals.

tonedef (3935

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