The lightning observed during volcanic eruptions is generally due to the friction between ash particles, dust, and gas which rub against each other and become electrically charged, causing electrical discharges.
In an erupting volcano, the column of ash and dust propelled into the atmosphere is so dense and turbulent that it creates a tremendous amount of friction between the particles. This friction strips electrons from the particles, generating electric charges. Gradually, the lighter positively charged particles rise higher, while the heavier negatively charged particles tend to remain at the bottom of the volcanic cloud. The result: the eruption column behaves like a gigantic atmospheric battery. When the charge difference becomes too great, the air can no longer insulate it, and it "cracks," releasing a powerful electric current: the volcanic lightning. This phenomenon is quite similar to a classic thunderstorm, but with ash added!
First, a very dense volcanic plume is needed, with a lot of material expelled into the air: ash, gas, rock debris. This large cloud filled with particles swirls, constantly rubbing against itself, and creates a huge static electricity. The more intense this friction is, the greater the chances of seeing lightning. Also, if the eruption is particularly violent or explosive, this turbulence increases even further. The second crucial ingredient is humidity. The presence of water or ice mixed with the ash facilitates electrical exchanges and thus boosts the formation of lightning. One last detail: the higher the plume rises, sometimes reaching several kilometers in altitude, the lower the temperature drops, favoring the appearance of spectacular lightning.
During volcanic eruptions, ash and rock fragments ejected into the air collide with each other. These constant contacts strip electrons from certain particles, allowing others to become negatively charged. Quickly, chaos ensues: some dust particles are negative, while others are positive. As a result, genuine electric fields are created within the volcanic plume. When these charges become intense enough to overcome the electrical resistance of the air, a breakdown occurs, and a lightning bolt streaks across the sky through the volcanic clouds. This phenomenon is somewhat reminiscent of what is observed with friction in a typical thunderstorm, but here, it is the volcanic ash that replaces the water droplets and ice crystals.
The eruption of the Eyjafjallajökull volcano in Iceland in 2010 left a lasting impression with its powerful lightning caused by the friction of ash particles. These spectacular lightning strikes greatly contributed to the media coverage of the event. Another striking example is the eruption of Pinatubo in the Philippines in 1991. This massive event generated repeated lightning due to the enormous amount of particles expelled at high speed. And how can we forget the impressive eruption of the Calbuco volcano in Chile in 2015, characterized by an incredible light display filmed from all angles by locals? Further back in history, the famous Krakatoa eruption in 1883 also produced monumental lightning, visible for hundreds of kilometers around and reported in numerous historical accounts.
Volcanic lightning produces an enormous amount of heat and energy. The primary consequence is that they transform certain gases into specific chemical molecules, notably by forming nitrogen oxides, which directly affects the chemistry of the atmosphere and can locally intensify acid rain. These molecules also disrupt air quality in the surrounding area and can pose problems for living organisms near the volcano. Furthermore, these lightning strikes sometimes contribute to electrically charging the layer of suspended dust and ash, thereby influencing dispersion mechanisms and altering the trajectories of volcanic clouds. Finally, although their overall climatic impact seems limited compared to other volcanic phenomena, these lightning strikes can still punctually influence local weather systems.
The flashes observed during volcanic eruptions are called 'volcanic lightning' or 'volcanic storms.' This spectacular phenomenon results from intense friction between ash particles ejected into the air, creating an accumulation of electric charges.
The eruption of the Calbuco volcano in Chile in 2015 produced particularly impressive volcanic thunderstorms, which were photographed and widely shared due to their stunning beauty.
Volcanic lightning enables scientists to estimate the volume of ash emitted during an eruption, thereby facilitating the monitoring and assessment of volcanic risks for the affected populations.
During the explosive eruption of the Icelandic volcano Eyjafjallajökull in 2010, which caused major disruptions to air traffic in Europe, spectacular volcanic lightning was documented by numerous scientific teams.
Scientists use various tools to study these lightning flashes, including specialized high-speed cameras, atmospheric electricity sensors, and weather radars. These instruments allow them to analyze the electrical mechanisms that are generally inaccessible directly within volcanic plumes.
In general, volcanic lightning has little impact on local weather. However, a major eruption accompanied by lightning can produce large amounts of ash that can temporarily cool the local or regional atmosphere and affect cloud formation.
The accurate forecasting of volcanic lightning remains challenging. However, scientists can indirectly anticipate its likelihood by studying the characteristics of the eruption, such as the intensity of volcanic particle emissions and the rapid rise of the ash plume.
No, volcanic lightning does not occur systematically during every eruption. It mainly depends on specific environmental factors, such as the chemical composition of the ash, its density, the strength of the eruption, and the surrounding weather conditions.
Yes, volcanic lightning can pose additional risks as it can trigger fires, damage electrical infrastructure, and further complicate rescue or evacuation operations.
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