The conclusion belongs to a new study

Mar 26, 2009 09:18 GMT  ·  By
Ash and gas plumes coming out of volcanoes twist in very much the same way a tornado does
   Ash and gas plumes coming out of volcanoes twist in very much the same way a tornado does

Scientists are currently puzzled by a new find, which shows that ash and gas plumes, fresh of a volcano, behave in very much the same way as tornadoes do, during the peak of their season. In addition to spawning dust devils, large concentrations of ash and other gases can also create lightnings in the clouds above, and scientists have no idea how this happens, at the moment.

It would appear that experts at the University of Illinois have managed to crack this puzzle just recently, as they have established that volcanic gases and ash rotate when they exit a crater, a phenomenon which has been termed a “volcanic mesocyclone.” They have analyzed the eruption of Mount Chaiten in Chile, which took place in 2008, as well as accounts dating back 200 years ago, when a ship captain described the eruption of a large volcano in the Azores Islands.

“What happens in tornadic thunderstorms is analogous to what happens in strong volcanic plumes,” UI postdoctoral researcher Pinaki Chakraborty, who is also the lead author of the new paper on the subject, which appears in the March 26th issue of the famed scientific journal Nature, explains. Because of the dust devils that form inside a volcano's tall ash and gas plume, electrical charges are separated, and the potential energy differences generate the lightings in the upper clouds.

When looking at 1991 satellite images of the Mount Pinatubo eruption, the researcher has noticed that, from hour to hour, the large “umbrella” that was created on top of the crater was spinning around its center with a medium speed. Over time, the formation morphed into a lobe-like structure, an occurrence that was also observed in other volcanic eruptions as well, such as those of Mount Manam in Papua New Guinea, Mount Reventador in Ecuador, and Mount Okmok in Alaska.

“The structure and dynamics of volcanic mesocyclones, as well as the presence of lightning sheaths, might be verified with Doppler radar and lightning mapping array, two technologies that have been scarcely used in volcanology,” Gustavo Gioia, who is one of the study team members, concludes.