Τετάρτη, Απριλίου 23



Stunning Electric-Blue Flames Erupt From Volcanoes

Indonesia's Kawah Ijen and other craters emit rivers of light from burning sulfur.
Sulfur combusts on contact with air to create stunning blue lava-like rivers of light in the Kawah Ijen crater on the island of Java.



     
For several years Paris-based photographer Olivier Grunewald   has been documenting the Kawah Ijen volcano in Indonesia, where dazzling, electric-blue fire can often be seen streaming down the mountain at night.



"This blue glow—unusual for a volcano—isn't, of course, lava, as unfortunately can be read on many websites," Grunewald told National Geographic in an email about Kawah Ijen, a volcano on the island of Java.   The glow is actually the light from the combustion of sulfuric gases, Grunewald explained.Those gases emerge from cracks in the volcano at high pressure and temperature—up to 1,112°F (600°C). When they come in contact with the air, they ignite, sending flames up to 16 feet (5 meters) high.Some of the gases condense into liquid sulfur, "which continues to burn as it flows down the slopes," said Grunewald, "giving the feeling of lava flowing."

Cynthia Werner, a research geologist with the U.S. Geological Survey (USGS) at the Alaska Volcano Observatory, told National Geographic that Grunewald's photos show an unusual phenomenon.

"I've never seen this much sulfur flowing at a volcano," she said.


Werner noted that forest fires in Yellowstone National Park have caused similar "rivers," as heat from the blazes melted the sulfur around hydrothermal vents.


"When you go to Yellowstone, you can see their traces as black lines," she said.




According to Werner, it's relatively common to find molten sulfur around volcanic fumaroles (hot vents). The mineral has a relatively low melting point of 239°F (115°C), and the temperature at the hot vents often exceeds that.

Blue volcanic fire was described in antiquity in Italy on the south slope of Mount Vesuvius and on the island of Vulcano, Grunewald said.

"Blue flames may also be observed at the base of the plume of erupting volcanoes, when ash explosions occur," he added.

Grunewald did not use any filters to capture his images of the blue fire. The burning happens day and night, but it's visible only in darkness.





Kawah Ijen volcano is the subject of a new documentary released earlier this month that was produced by Grunewald and Régis Etienne, the president of Geneva's Society of Volcanology.












    
PHOTOGRAPH BY OLIVIER GRUNEWALD


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