Just a few years ago, a photograph appeared on the Internet when French photographer Olivier Grunewald took spectacular photos of the Indonesian volcano Kawah Ijen. Taken through the filming of a brand new documentary he’s releasing with the president of the Geneva Volcanological Society, Régis Etienne, the pictures – taken without the usage of any filters or digital enhancements – show the eerie, electric blue glow of the volcano.
However, a small proportion of online reports have enlightened readers concerning the scientific principles at work. “This blue glow, unusual for a volcano, just isn’t lava itself, as unfortunately could be read on many web sites,” says Grunewald. “This comes from the combustion of sulfur gases in contact with air at temperatures above 360°C.”
In other words, lava – molten rock that erupts from the Earth at very high temperatures – just isn’t significantly different in color than lava from other volcanoes, which differ barely in mineral composition but are vivid red or orange in color when molten. However, in Kawah Ijen, unusually large amounts of sulfur gases are released from the lava under high pressure and at temperatures (sometimes exceeding 600°C).
When exposed to oxygen within the air and attributable to lava, sulfur burns easily and its flames are vivid blue. Grunewald says there’s a lot sulfur that it sometimes flows down the rock because it burns, making it appear as if blue lava was spilling down the mountainside. However, since only the flames are blue, and never the lava itself, the effect is simply visible at night – through the day the volcano looks kind of like all other.
“The vision of these flames at night is strange and extraordinary,” says Grunewald. “After spending a number of nights within the crater, we felt that we were really living on one other planet.”
Mount Ijen, positioned on the eastern tip of the island of Java, is home to 2 of probably the most extraordinary phenomena on Earth. In addition to the amazing blue flame, it also has a kilometer-wide caldera lake stuffed with turquoise-blue water. The color of the water is resulting from its extreme acidity and high concentration of dissolved metals. It is the world’s largest highly acidic lake, with a measured pH of just 0.5. The reason for its acidification is the inflow of hydrothermal waters charged with gases from the new magma chamber below.
About 300,000 years ago, volcanic activity in the world began constructing a big stratovolcano, today called “Old Ijen”. Over hundreds of years and repeated eruptions, it grew to a height of about 3,000 meters. Lava flows and pyroclastic deposits from Old Ijen unconformably with Miocene limestone.
Then, about 50,000 years ago, a series of giant explosive eruptions created a caldera about ten miles in diameter. About twenty cubic miles of fabric was ejected, covering the encompassing landscape to a depth of 300 to 500 feet with ejecta and volcanic ash.
Over the past 50,000 years, many small stratovolcanoes have formed within the Old Ijen caldera, covering its southern and eastern reaches. Kawah Ijen covers a part of the eastern margin. Thousands of years of weathering have transformed pyroclastic deposits into the wealthy, fertile soils that now support coffee plantations.
The volcano stays lively. The last magma eruption occurred in 1817. Phreatic eruptions occurred in 1796, 1917, 1936, 1950, 1952, 1993, 1994, 1999, 2000, 2001 and 2002. They caused little or no damage but pose a risk to anyone who mines sulfur or visits the caldera.
Source: pwmithsonianmag.com | Nationalgeographic.com | geology.com
