23 August 2018
Electrically charged volcanic ash short-circuited Earth’s atmosphere in 1815, causing global poor weather and potentially contributing to Napoleon’s defeat at Waterloo, says new research.
Dr Matthew Genge from Imperial College London has discovered that electrified volcanic ash from eruptions can ‘short-circuit’ the electrical current of the ionosphere – the upper level of the atmosphere that is responsible for cloud formation.
The findings, funded by STFC and published today in Geology, could confirm the suggested link between the eruption and Napoleon’s defeat.
Historians know that rainy and muddy conditions helped the Allied army defeat the French Emperor Napoleon Bonaparte at the Battle of Waterloo. The June 1815 event changed the course of European history.
Two months prior, a volcano named Mount Tambora erupted on the Indonesian island of Sumbawa, killing many thousands of people and plunging the Earth into a ‘year without a summer’ in 1816.
Dr Genge, from Imperial’s Department of Earth Science and Engineering, suggests that the Tambora eruption short-circuited the ionosphere, ultimately leading to a pulse of cloud formation. This brought heavy rain across Europe that contributed to Napoleon Bonaparte’s defeat.
The paper shows that eruptions can hurl ash much higher than previously thought into the atmosphere – up to 100 kilometres above ground.
Dr Genge said: “Previously, geologists thought that volcanic ash gets trapped in the lower atmosphere, because volcanic plumes rise buoyantly. My research, however, shows that ash can be shot into the upper atmosphere by electrical forces.”
A series of experiments showed that that electrostatic forces could lift ash far higher than by buoyancy alone. Dr Genge created a model to calculate how far charged volcanic ash could levitate, and found that particles smaller than 0.2 millionths of a metre in diameter could reach the ionosphere during large eruptions.
He said: “Volcanic plumes and ash both can have negative electrical charges and thus the plume repels the ash, propelling it high in the atmosphere. The effect works very much like the way two magnets are pushed away from each other if their poles match.”
The experimental results are consistent with historical records from other eruptions.
“Electrostatic levitation of volcanic ash into the ionosphere and its abrupt effect on climate” by Matthew J. Genge, is published in Geology