Volcanic lightning

Lightning has been observed in ash plumes during explosive eruptions, but not every eruption produces visible discharges. The U.S. Geological Survey describes activity in several parts of a plume: the gas-thrust region above the vent, the rising convective column, and the umbrella region that spreads outward at altitude. Electrical activity close to the vent may appear as short, chaotic discharges, while larger flashes can occur farther up in the plume.

An eruption rapidly fragments magma into ash and larger particles. Fracturing can generate charge, and collisions and friction between particles can transfer charge and separate particles of different sizes or materials. These mechanisms are often grouped as fractoelectric and triboelectric charging. In higher, mature plumes, ice particles may contribute processes analogous to those in thunderclouds. Their relative importance varies with eruption and plume conditions; researchers continue to investigate how these mechanisms combine.

Lightning detection can provide information even when a volcano is remote or obscured. Instruments that detect radio signals from discharges can help establish when and where lightning occurred, while combining electrical observations with other measurements may help researchers investigate plume dynamics. A 2022 review of volcanic electrification describes this as a growing tool for understanding explosive eruptions, not a standalone measure of eruption size or a replacement for established monitoring.

Electrical discharges can create a lightning hazard around an eruption, including for power infrastructure. Laboratory experiments and analyses of lightning-affected volcanic particles also indicate that intense heating can melt, round, aggregate or fragment some ash grains and can alter their chemistry. The extent of these effects in natural plumes depends on conditions and is a research topic. Volcanic ash itself remains dangerous to aviation and infrastructure regardless of whether lightning is observed.