The country's Mount Ontake erupted around 11:53 a.m. Japan Standard Time, is believed to have killed over 30 people

Sep 29, 2014 07:03 GMT  ·  By

This past weekend, Japan's Mount Ontake erupted with no warning whatsoever. The eruption sent massive amounts of steam, ash and rock down the volcano's slopes, and is believed to have killed and injured several dozen people.

Information available to the public says that the eruption occurred around 11:53 a.m. Japan Standard Time. At that time, several groups of tourists were hiking on Mount Ontake, which is the second highest volcano in Japan, looking to snap some photos of the autumn foliage.

It is understood that, of these people, 31 were in cardiac arrest at the time rescuers arrived in the area and found them. However, authorities in Japan have not yet declared them dead. Such announcements can only be made following an official investigation.

Apart from these 31 people that are presumed dead, about 40 are believed to have been severely injured in the eruption. Rescue operations are still underway, and it will be a while until we get a complete picture of what exactly happened on Mount Ontake.

Why this high death toll?

As mentioned, Japan's Mount Ontake erupted without any warning. Otherwise put, no earthquakes were documented in the area, and the volcano did not show any signs of unrest prior to Saturday's catastrophe.

Hence, the hikers were taken quite by surprise. According to Daily Mail, some of them managed to take cover in some of Mount Ontake's nooks and crannies, but the majority of the people who were exploring the volcano's slopes at the time the eruption occurred had virtually no time to react before the ash, the rocks and the Steam got to them.

Not your regular volcanic eruption

The first thing you need to know about Japan's Mount Ontake, otherwise known as Mount Kiso Ontake, is that it is a stratovolcano. Such geological formations come into being when and where a continental plate dives under another.

What distinguishes stratovolcanoes from other geological formations of this kind is the fact that they have fairly gentle slopes towards their base, and very steep ones towards their narrow tips.

Unlike other volcanoes, those belonging to this class are known to erupt with absolutely no warning every once in a while. What's interesting is that, more often than not, they cough out no lava at all when throwing such a fit.

On the contrary, they merely produce rocks, ash and steam that move down their slopes at impressive speeds. This volcanic material can be accompanied by compounds like carbon dioxide or hydrogen sulfide, which kill whatever people they chance to come across by asphyxiating them.

Word has it that the eruption believed to have killed dozens of people in Japan this past weekend was a so-called phreatic one. As detailed by specialists with the Japanese Meteorological Agency, such eruptions occur when water works its way into the crater area of a stratovolcano.

Once heated by the hot ground, this water turns into steam. The pressure inside the volcano builds up, and eventually the steam breaks out, dragging volcanic material with it. Despite the fact that no lava is released, the sheer speed and mass of the volcanic material produced during such events are more than enough to cause serious damage to infrastructure and kill people.

Given the fact that rescue operations are still ongoing and specialists have not yet had the chance to have a close look at Mount Ontake, detailed information concerning what exactly happened on the slopes of this volcano, located just 200 kilometers (125 miles) west of Tokyo, is still lacking.

Hopefully, more information will soon be made available to the public.