Tens of thousands flee ash and rock falling from the sky as Indonesia’s Mt. Kelud erupts

A massive eruption from Mount Kelud, on Indonesia's island of Java on Thursday night blasted a cloud of ash at least 15 kilometres up into the sky. Local air traffic has been grounded as a result and more then 100,000 people have been forced to flee their homes around the volcano.

With Mt. Sinabung erupting rather spectacularly over the past few weeks, sending pyroclastic flows down its slopes, and with nearly 30 major earthquakes through eastern Indonesia over the past month, authorities were alert to another potential eruption in the area. Just hours before Mt. Kelud blew its top, they had raised the alert status of the volcano to the highest level possible.

As residents struggle to cope with ash streaming from the volcano's summit to coat everything in the area, deep enough in some places that it could be mistaken for gray snow, and deal with gravel-sized rock raining down from the sky as well, authorities have evacuated the region around the volcano out to around 10 kilometres away. According to reports, over 100,000 people have been displaced from their homes, and are being housed in shelters until the emergency passes. Two people have been killed after the weight of the accumulating ash caused their houses to collapse on them, while a third person died due to a traffic accident during the evacuation.

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The ash cloud from Kelud has been blowing off to the west of the island of Fiji, reaching as far as 500 kilometres away, forcing airports in the region to shut down and cancel flights. Even air traffic on its way through the area had to turn back to their original airports or be diverted, to avoid possible engine trouble due to the volcanic ash.

Local resident Hilmi Dzakaaul I. captured this spectacular image of the charged ash cloud from Kelud sparking off lightning strikes.

These kind of lightning strikes are common during volcanic eruptions. Just as the friction between water droplets in storm clouds are thought to generate charge differences between the tops and bottoms of the clouds, the ash particles rubbing against each other in the volcanic plume generate tremendous static charges. These often cause lightning arcs within the plume, between the plume and the volcano, and between the plume and the surrounding countryside.

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The last time Kelud erupted was in early November of 2007, after lying dormant for over 17 years. Authorities had evacuated around 30,000 people during the few weeks before the volcano began spewing forth a string of small eruptions over roughly a week's time. No deaths were reported due to these eruptions, however, according to VolcanoDiscovery.com, Kelud has claimed many lives over the years. Pyroclastic flows during the 1991 eruptions caused 50 deaths, the 1919 eruption caused the crater lake to drain, touching off massive landslides that killed over 5,000 people, and an eruption in the late 1500s possibly claimed over 10,000 lives.

VolcanoDiscovery.com described the eruption of Kelud as "possibly sub-plinian or even plinian in size." Plinian eruptions are some of the most powerful volcanic eruptions in recent times. The eruption of Iceland's Eyjafjallajökull volcano in 2010 would be considered 'sub-plinian,' while the 1980 eruption of Mount St. Helens ranked as 'plinian.' Beyond that, 'ultra-plinian' eruptions include Mt. Pinatubo (1990) and Krakatoa (1883), but anything more powerful than those go back hundreds, to tens or hundreds of thousands of years ago.

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