Is An Even Larger Eruption Brewing At Mount Ontake?

Despite the advanced technology devoted to the monitoring of seismic and volcanic activity, the unexpected eruption of the Japanese volcano Mount Ontake proves that Nature can still surprise us.

The unexpected eruption led to a heavy death toll; there are 36 people confirmed dead and many other were injured as 250 hikers were caught unawares by a deluge of red hot hail and rocks.The search for the bodies of the unfortunate hikers has now had to be called off amidst fears that the eruption is intensifying. Reports from the Japanese meteorological agency stated that volcanic tremors in the area could mean that another explosion was on the way.

"The strength of the tremors increased late last night, diminished and then rose again early this morning. There’s the chance things could get even worse, so caution is needed," Yasuhide Hasegawa told Reuters news agency.

"This points to possibly increasing pressure due to steam inside the volcano, and if it exploded rocks could be thrown around, endangering rescuers," he said.

Experts are still unsure of what to expect, as the tremors have been oscillating up and down.

“At this point, anything can happen,” said Shoji Saito, also of the Japan Meteorological Agency.

So why did the eruption occur without any warning?

Mount Ontake belongs to a type of volcano known as "stratovolcanoes," formed when one continental plate is shunted under another, and notorious for their unpredictable eruption patterns.

These unforeseen eruptions are labeled "pyroclastic" eruptions, and are typically rapid releases of ash and rock that can speed down the side of a volcano at up to 450 miles (700 kilometers) per hour. This type of volcanic emission is particularly deadly as it moves like a body of liquid, often incinerating everything in its path. A pyroclastic eruption occurred on Mount Ontake in 1979, though Saturday’s event was a more minor version, known as a "phreatic" eruption. Phreatic outbursts consist of steam, ash and rock but not lava; however, the carbon dioxide or hydrogen sulfide fumes that arise from the volcanic debris can be just as deadly, causing death by asphyxiation.

Scientists have attempted to use computer models to predict eruptions in volcanoes that regularly produce major pyroclastic flows, such as the Merapi eruption in Indonesia, along with a system of monitoring stations, but it remains a very inexact science and on several occasions monitoring stations have been washed away by unexpected explosions.

Whether Saturday’s eruption was just a precursor to a much larger event is not yet known, but Mount Ontake has left nearby residents with a healthy respect for its power and potential for danger.