A newfound link between two of nature's most violent phenomena could explain how volcanic ash clouds can generate bolts of lightning and tornado-like dust devils and waterspouts.
Scientists have long known that tornadoes are the products of colossal columns of spinning air—mesocyclones—inside large storm clouds.
A new study suggests mesocyclones can also form in the ash plumes of volcanic eruptions.
Under certain circumstances, these volcanic mesocyclones can aid in lightning production and create tornado-like structures that corkscrew toward the Earth, said study team member Pinaki Chakraborty of the University of Illinois at Urbana-Champaign.
Chakraborty suspects the recent eruptions of Redoubt Volcano in Alaska "might be powerful enough" to generate mesocyclones.
(See photos of Redoubt Volcano erupting.)
So far, however, no lightning or cyclones have been observed at Redoubt Volcano, said Michelle Coombs, a geologist at the Alaska Volcano Observatory, who did not participate in the study.
Volcanic Cyclones' Model Behavior
While examining satellite images of the 1991 eruption of Mount Pinatubo in southeast Asia, the study team discovered that the volcanic plume was rotating around its axis in a way that couldn't be explained by conventional theories.
"This was not known before," Chakraborty said.
Using results from thunderstorm computer modeling, the team showed how powerful updrafts generated during a volcanic eruption can cause coil-like tubes of circulating air to flip their orientations from horizontal to vertical within the plume.
The resulting volcanic mesocyclone could cause the entire plume to rotate like a tornado.
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