Volcanic ash clouds are up to a thousand degrees hot and rush the slopes with 500 km / h down, silent. In Japan, numerous trippers are smothered in a. An early warning was hardly possible.

The most amazing news after volcanic disaster of Japan is: people fell into the ash cloud and survived. On Saturday shot from the mountain Ontake 200 kilometers west of Tokyo suddenly a hot gray cloud, they met many trekkers. At the outbreak of at least 32 people died and more are missing.

Who gets into such pyroclastic flows, has hardly a chance to escape. They are about a thousand degrees hot, plunge with 500 kilometers per hour silently down the volcano flanks. The currents glide on a cushion of hot air, overcome hills or smaller waters with virtually no energy loss.

People who are recognized suffocate usually – depending on how much ash they must breathe. In the lungs the ash solidifies to cement, choke the victim. Their bodies usually char. At autopsy, the body must be opened with a hammer and chisel. The casts of victims of Vesuvius eruption in 79 AD, Pompeii and Herculaneum were petrified of such pyroclastic flows.

Mount Ontake Errupt:Sudden darkness

A recent guide for tourists volcano warns of the death cloud: “escape is usually impossible,” it says tersely. So it was on Ontake: The outbreak apparently came without warning, it thundered only – then collapsed already the dust avalanches down. Many tourists suspected apparently unaware of the danger, they filmed the eruption. Survivors told of “sudden darkness”.

What had happened? Typical cause a sudden ash eruption is groundwater. Through the rugged rocks of the crater it seeps into hot depth, where it begins to boil – the pressure in the caldera rises. If the voltage in the rock too large, the concoction explodes, it throws those clouds of tiny lava and rock scraps out – in a so-called phreatic explosion.

Japan Volcanic Disaster:Tips for tourists

For the groundwater theory is that scientists had previously reported no disturbing data. Japan has the densest network for volcano monitoring, volcano chains drag across the country. But on Ontake quake were apparently neither increased measured, which would have rising magma. Still increased gas vapors or ground vaults were registered.

Lack of reliable early warning, scientists must make do with coarse volcanic tourists Tips: Go smaller dust avalanches, advise, to bring themselves quickly to safety. But on Ontake remained from such warnings of the volcano, there was no prelude to the explosion.

The second tip would the victims of little help: Tourists should know the history of a volcano – it is prone to sudden ash explosions? The Ontake seemed predictable, since 1980, there was only a small eruption in 2007, which was, however, accompanied by earthquakes. Anyone who wants to better protect should take breathing mask, helmet, goggles, flashlight and emergency kit for volcano tours so.

The rescue units arrived on Ontake have their application suspended again. At the weekend the more than 500 workers had to repeatedly turn back because of the risk of toxic gases and renewed eruptions. Twelve deaths have so far been taken by helicopter from the mountain.

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