By David Jacobson, Temblor
Yesterday afternoon, Sileri Crater, which is part of the Dieng Volcanic Complex in Indonesia, erupted, leaving around 10 people injured and forcing an evacuation of the area. Additionally, following the eruption, a rescue helicopter crashed, killing all eight people onboard. Sileri Crater is on the Indonesian island of Java, home to approximately 145 million people and Jakarta, the country’s capital which is a little over 300 km west of the complex. This area is an extremely popular tourist destination not only due to the volcanoes, but because it is a sacred area where there are some of Java’s oldest Hindu temples.
Even though yesterday’s eruption was not large, cold lava, mud and smoke was still ejected more than 50 m into the air. According to the National Disaster Mitigation Agency, the eruption was sudden, which is why tourists were in the area, including 17 in close proximity to the crater. Since yesterday’s eruption, the crater has remained quiet, and is still off limits. However, the rest of the complex is still open to the public.
Sileri Crater is one of Indonesia’s most active volcanoes and last erupted in 2009. That eruption was larger than yesterday’s, as it ejected material over 200 m into the air and resulted in the formation of three new craters. The entire Dieng Volcanic Complex consists of at least two stratovolcanoes and 20 small craters and cones. Some of these craters are now filled by small acidic lakes. In addition to these volcanic features, there is significant geothermal activity in the area, consisting of fumaroles, hot springs and boiling mud.
While lava once flowed over the entire complex, historic activity has only consisted of minor phreatic and phreatomagnatic eruptions. Phreatic eruptions are steam eruptions in which no lava is involved, while phreatomagmatic eruptons are similar but involve the ejection of lava. Small eruptions like this are often not dangerous, but in the case of the Dieng Volcanic Complex, they are frequently accompanied by toxic gas emissions. These gases can be fatal, as was the case in 1979, when 142 people were asphyxiated by poisonous gas during a minor phreatic eruption from a nearby crater. This highlights the importance of understanding the volcanic hazards of an area and explains why the Dieng Volcanic Complex is closely monitored.
Indonesia is no stranger to volcanic eruptions, as it is home to approximately 150 active volcanoes, the most of any country on earth. Additionally, at least 39 of these are on the island of Java alone. The reason for all of these volcanoes is subduction of the Australian plate beneath the Sunda plate at the Java Trench. Some of the eruptions from these volcanoes have had global impacts. In 1815, Mt. Tambora unleashed the most violent eruption in the last 5,000 years, and in 1883, Krakatau erupted, killing over 35,000 people, and dropping global temperatures by as much as 1.2 degrees Celsius. In addition to these eruptions, the subduction zone that formed this massive volcanic arc, has also been responsible for numerous large magnitude earthquakes. Therefore, Indonesia has multiple hazards that must be monitored. Should activity progress at Sileri Crater, we will update this post.
References
Smithsonian Institution (National Museum of Natural History) – Global Volcanism Program
F. LE GUERN, H. TAZIEFF, and R. FAIVRE PIERRET, An Example of Health Hazard: People Killed by Gas during a Phreatic Eruption: Dieng Plateau (Java, Indonesia), February 20th 1979, Bull. Volcanol., Vol. 45-2, 1982
Oregon State University
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