Volcanic eruptions are natural disasters that are both spectacular and terrifying. They have inspired fear, superstition, and myths, leaving us breathtaking views. A dirty thunderstorm is one of the awe-inspiring phenomena caused by powerful volcanic eruptions.
What is a Dirty Thunderstorm?
A dirty thunderstorm is a weather phenomenon related to lightning production in a volcanic plume. It earned its name from the rock fragments, ash, and other ejecta colliding during a volcanic eruption, generating static electricity within the plume. It is usually formed in the eruption clouds of volcanic and plinian eruptions.
A dirty thunderstorm showcases bolts of lightning that shoot out of an erupting volcano, making it one of the most terrifying yet astonishing displays to witness. Over 200 cases of dirty thunderstorms have been recorded over the past two centuries, although scientists have not yet fully understood the dynamics of this unique event.
The earliest known observations of a dirty thunderstorm were made by Gaius Plinius Caecilius Secundus, also known as Pliny the Younger. He recorded his observations of the eruption of Mount Vesuvius in A.D. 79. As Pliny the Younger noted, there was an intense darkness rendered by the irregular gleam of torches at intervals concealed by transient blaze of lightning.
An Italian physicist and meteorologist, Luigi Palmieri, also performed initial research on volcanic lightning at Mount Vesuvius eruption. He focused on the 1858, 1861, 1868, and 1872 eruptions from the Vesuvius Observatory, as lightning events frequently occurred throughout these eruptions.
READ ALSO : Volcanic Lightning During Eruptions May Have Sparked Life on Ancient Earth, Study Suggests
How is a Dirty Thunderstorm Formed?
Charge separation must occur to generate lightning. In an ordinary thunderstorm, static electricity is produced when ice particles in clouds collide with one another. This results in a type of lightning that we normally observe.
When it comes to dirty thunderstorms, lightning forms from the volcanic plume rich in ashe; it can occur either close to the ground in dense ash clouds or near the stratosphere.
During some explosive volcanic eruptions, a volcanic plume known as an eruption column is emitted. The volcanic ash comprising the eruption plume contains glass, fragmented rocks, and minerals. These components are formed when gases that get dissolved in magma expand and violently escape into the atmosphere.
The densely packed particles collide and rub against each other as they are ejected into the eruption plume. This collision leads to the generation of static charge. In other words, the volcanic ash becomes electrically charged as some particles gain electrons while others lose electrons.
The charged ash particles rise from a compressed environment beneath the volcano to a less dense environment aboveground in the plume. As a result, the positively charged ash particles separate from the negatively charged particles. The volcanic plume continues to rise and further divides the opposing charge regions. Eventually, an electric discharge will be where lightning tears through the volcanic plume and connects the oppositely charged areas. This is followed by an intense lighting activity near the ground, characterized by sparks and fiery thunderbolts.
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