Tornado-like rotation may help scientists better predict effects of volcanic eruptions

March 26th, 2009 - 1:46 pm ICT by ANI  

Washington, March 26 (ANI): In a new research, scientists have determined that studying tornado-like rotation in volcanoes can help them to better predict the effects of volcanic eruptions.

The research is based on a 200-year-old report by a sea captain and photographs of the 2008 eruption of Mount Chaiten.

Scientists involved in the research have shown that the spontaneous formation of a “volcanic mesocyclone” - a rotating, column-shaped vortex - causes the volcanic plume to rotate on its axis.

The rotation, in turn, triggers a sheath of lightning and creates waterspouts or dust devils. The origins of these volcanic phenomena were previously unexplained.

“These results solve a long-standing mystery about the relationship between volcanic plumes and associated tornadoes, waterspouts and lightning, showing for the first time that rotation of a volcanic plume may be the primary cause of these effects,” said Sonia Esperanca, program director in the National Science Foundation’s (NSF) geosciences directorate.

“Rotation is an essential element of a strong volcanic plume,” said Pinaki Chakraborty, a computational scientist and engineer at the University of Illinois and the research paper’s lead author. “By taking into account the rotation, we can better predict the effects of volcanic eruptions,” he added.

In 2008, a photograph of the Mount Chaiten eruption in southern Chile showed what appeared to be a volcanic plume wrapped in a sheath of lightning.

A search for references to other occurrences of lightning sheaths led Chakraborty, mechanical engineer Gustavo Gioia and geologist Susan Kieffer to an obscure paper by a sea captain, published in 1811.

In that paper, the sea captain reported his observations of a volcanic vent that emerged from the sea in the Azores archipelago and formed a large volcanic plume.

According to the captain, the plume rotated on the water “like an (sic) horizontal wheel” and was accompanied by continuous “flashes of lightning” and a “quantity of waterspouts.”

This conjunction of rotation, lightning and waterspouts is characteristic of a familiar meteorological phenomenon seemingly unrelated to volcanic plumes: a tornadic thunderstorm.

The same process that creates a mesocyclone in a tornadic thunderstorm also creates a volcanic mesocyclone in a strong volcanic plume, according to Chakraborty.

“What happens in tornadic thunderstorms is analogous to what happens in strong volcanic plumes,” he said.

A strong volcanic plume consists of a vertical column of hot gases and dust topped with a horizontal “umbrella.” A volcanic mesocyclone sets the entire plume rotating on its axis.

The mesocyclone spawns waterspouts or dust devils, and groups the electric charges in the plume to form a sheath of lightning. (ANI)

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