Most lightning caused by a volcano

Ash, ice and other particles emitted into the atmosphere during volcanic eruptions can lead to a buildup of static electricity that results in volcano-induced storms. The massive eruption of the submarine Hunga Tonga-Hunga Ha-apai in the South Pacific in January 2022 triggered the largest volcanic-lightning event in recorded history, with 589,754 lightning discharges (in-cloud and cloud-to-ground) detected over three days between 13 and 15 January, peaking at 5,200 events per minute between 05.00 and 05.02 UTC on 15 January 2022.

Between 13 and 15 January 2022, some areas close to the volcano experienced 247 events per square kilometre – equivalent to the annual lightning frequency seen in places like Lake Maracaibo in Venezuela, which holds the record for highest lightning concentration on Earth (not triggered by volcanic activity).

To put this in context of other volcanic-lightning events, the previous record to have been measured using the same technology was the eruption of Anak Krakatau in Indonesia in December 2018, which sparked 340,000 lightning discharges over the course of a week. Tonga's volcano was an order of magnitude more extreme, with almost 400,000 lightning discharges logged in a six-hour period on the morning of 15 January.

The Hunga Tonga-Hunga Ha-apai eruption didn't only generate a record amount of lightning. The 15 January explosion released an unprecedented 146 teragrams of water vapour up to 53 km (33 mi) high into the stratosphere; the plume contained the equivalent of 58,000 Olympic swimming pools' worth of water. It is also produced the fastest atmospheric shockwaves ever recorded on Earth, travelling at a record rate of up to 319 m/s (1,148 km/h; 714 mph), close to the speed of sound, with enough energy to complete six circles of the planet.

The lightning discharges were counted by the GLD360 lightning detection network (operated by Finnish meteorological/environmental tech company Vaisala), which has been in operation since 2009, though its archives only begin from 2012. The system is based on a series of receivers located around the world that pick up electromagnetic (radio) signals produced during a lightning discharge (both intracloud and cloud-to-ground). The sensors log the time that the waves take to reach them, as well as their direction of arrival, so that when multiple receivers’ data is combined, it’s possible to calculate the location and time that the discharge occurred.