Why Do Lightning Flashes Appear When a Volcano Erupts?

The phenomenon of lightning appearing when a volcano erupts is called volcanic lightning. This happens due to several factors.

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Lightning struck along with ash spewed by the Taal volcano in the city of Tagaytay, Cavite, Philippines, which erupted on Sunday (1/12/2020) evening.

A video recording shows the eruption of Mount Ruang, which is quite powerful and explosive in the Sitaro Islands Regency, North Sulawesi, on Wednesday (April 17, 2024) night. The video shows that the eruption of Mount Ruang not only emitted lava and hot clouds but was also accompanied by lightning flashes.

The phenomenon of lightning appearing around an erupting volcano is often referred to as volcanic lightning. Volcanic lightning is a mysterious phenomenon and is difficult for researchers to understand. However, in general, volcanic lightning is a manifestation of electrical processes that occur when the ash column rises due to explosive volcanic eruptions.

Many studies have revealed that the level of volcanic lightning strength is influenced by the size of volcanic eruptions, especially in relation to the height of ash and atmospheric temperature. Therefore, the higher the ash plume or column from a volcanic eruption, the greater the potential for volcanic lightning formation.

Head of the Center for Volcanology, Mitigation and Geological Disasters (PVMBG) Hendra Gunawan explained that lightning seen when a volcano erupts is a common occurrence. The cause is the electric charge released by hot volcanic gas molecules.

The occurrence of volcanic eruptions in the form of an explosion is basically the process of releasing high-temperature volcanic materials, both solid, liquid and gas. The molecules of these hot volcanic gases release their electric charges which appear as lightning.

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The eruption of Mount Ruang in the Kepulauan Siau Tagulandang Biaro (Sitaro) Regency in North Sulawesi occurred on Tuesday night (16/4/2024). Hundreds of residents were evacuated.

The occurrence of lightning during volcanic eruptions is generally not much different from the mechanism of lightning formation in the sky when it's cloudy or going to rain. However, the difference lies in the location or space that triggers the appearance of lightning.

The process of lightning occurring in the sky happens when the electric charge accumulated inside cumulonimbus clouds reaches a certain saturation level. In volcanic lightning, the cumulonimbus cloud that becomes the space where lightning occurs is replaced by a cloud of steam, ash, dust, and other volcanic particles that burst into the sky massively.

Although the complete mechanism has not yet been fully understood by researchers, several research findings have shown some phenomena that contribute to or trigger the formation of volcanic lightning when a volcano erupts.

In general, volcanic lightning is a manifestation of electrical processes that occur when the ash column rises due to explosive volcanic eruptions.

In a study published in the journal Geophysical Research Letters in 2011 by the Icelandic Meteorological Agency and other researchers, one of the phenomena that can trigger the formation of volcanic lightning is ice charging. This phenomenon occurs when warm air from an eruption rises into the sky and meets cooler air in the atmosphere.

The phenomenon of friction, known as triboelectric charging, is also considered an important mechanism that can cause volcanic lightning. This phenomenon occurs because ice particles, rock fragments, and ash collide to produce charged ions.

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Glowing lava flowed followed by hot clouds and lightning that struck when Mount Sinabung erupted, as seen from Gamber Village, Karo, some time ago.

Apart from that, the height of volcanic ash also has a significant impact on the formation of volcanic lightning. This is in accordance with the results of a study from a volcanologist from the University of South Florida, Stephen McNutt, and a meteorologist from the Massachusetts Institute of Technology, Earle Williams, published in the journal Bulletin of Volcanology in 2010.

They wrote that there will be a higher concentration of water vapor when a volcanic eruption produces ash with a radius greater than 7 kilometers. This will also trigger more ice filling and electrical activity phenomena. Conversely, eruptions with smaller levels of volcanic ash will reduce the occurrence of volcanic lightning.

Also read: More than 11,000 people need to be evacuated due to the eruption of Mount Ruang

The highest flash of lightning

Research published in the journal Geophysical Research Letters in June 2023 shows that lightning strikes emitted by the eruption of Mount Hunga Tonga in 2022 have created the highest level of lightning flashes ever recorded on earth. These lightning flashes were even more numerous than any storm ever documented.

A team of researchers led by the US Geological Survey Cascades Volcano Observatory has discovered that the eruption produced 2,615 lightning strikes per minute at its peak intensity. The peak intensity lasted for almost five minutes.

The peak level of lightning from the eruption of Hunga Tonga volcano in the South Pacific is also much higher than the second most intense lightning event ever detected. That event was 993 flashes per minute during a lightning storm in the southern United States in 1999.

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A submarine volcano eruption occurred off the coast of Tonga, projecting a cloud of smoke, steam, and ash thousands of meters into the air above the ocean in the South Pacific region on Wednesday, March 18, 2009. The eruption took place in the sea approximately 6 miles (10 kilometers) from the southwest coast, off the main island of Tongatapu, an area where 36 submarine volcanoes are located.

Sonja Behnke from the Electromagnetic Science and Cognitive Space Applications Group at Los Alamos National Laboratory, who is also one of the authors of the study, said that the eruption of Hunga volcano is the largest since the eruption of Mount Krakatoa in 1883.

Also read: Hunga Tonga Volcanic Eruption Has Reduced Ozone Layer Levels

The violent eruption of a volcano produces cloud of ash that can create its own weather system and trigger lightning formation in higher positions than usual. When the underwater volcano of Hunga Tonga erupted, it created a cloud of ash that reached over 40 kilometers, higher than the typical thunderstorm.

"Observations of lightning like this reveal details about the evolution of eruptions over time. Ultimately, this information is crucial when cloud cover obscures satellite observations of lightning bursts," said Sonja Behnke as quoted from the official website of Los Alamos National Laboratory.