Lightning: it isn’t just for stormclouds.
“If you are caught on a golf course during a storm and are afraid of lightning, hold up a 1-iron. Not even God can hit a 1-iron.” –Lee Trevino
When the voltage between two distant points exceed the breakdown voltage of air, a lightning strike occurs. During thunderstorms, approximately ten Coulombs of charge — some 10^20 electrons — are exchanged with every bolt, representing the release of an incredible build-up of energy.
During a volcanic eruption, however, the incredible heats cause neutral atoms to become ions, either positively or negatively charged, which then separate due to differences in masses, temperatures and physical cross-sections. The aerodynamics separates the particles even farther, and when the threshold of breakdown voltage is crossed, a lightning strike occurs. The photos below, most spectacularly, show multiple lightning strikes observed over the span of many minutes, taken as a time-lapse. All told, volcanic lightning has been observed and well-documented in over 150 eruptions, from the recent ones Eyjafjallajökull (in Iceland), Puyehue-Cordón Caulle (in Chile) and Sakurajima (in Japan) all the way back to the infamous eruption of Mt. Vesuvius nearly 2000 years ago!
Mostly Mute Monday tells the story — in images with 200 words max — of a particular physical or astronomical sight found in this Universe. For more about volcanic lightning and its causes, have a read here.
Leave your comments at the Starts With A Bang forum on Scienceblogs.