Artificial volcano spewing hot ashes

Researchers get to the bottom of secrets of pyroclastic flows

The artificial volcano erupts. In the second picture on the top left, the cloud collapses and then races down. In the lower row of images, the artificial eruption was recorded with thermal cameras. The hottest areas are white to light yellow, the cold deep blue. © Bernd Zimanowski / Sonja Calvari
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When a volcano explodes, chasing its eruption cloud into the sky, it can collapse in the air, fall down and race down the slopes of the mountain as a devastating avalanche of glowing rocks, gases and ashes. Volcano experts from the University of Würzburg now want to elicit their secrets from these so-called pyroclastic flows. To do this, they simulate the glut avalanches in experiments that they carry out together with Italian researchers.

The currents are several hundred degrees Celsius hot and can get up to 250 kilometers per hour. For example, in the year 79 they swept down Mount Vesuvius and destroyed Pompeii and other settlements. Since 1944, this volcano behaves quietly. But if it breaks out, it threatens the greatest danger - because in its immediate vicinity, in the conurbation of Naples, live today about 1.2 million people.

In Italy, the disaster activists are considering upgrading at least the houses in the wider area of ​​Mount Vesuvius so that they can withstand a pyroclastic flow. Primarily, schools and clinics should be that, houses in which as many people as possible can find refuge.

However, no one yet knows what violence the volcanic avalanches unfold, which pressure the buildings have to endure. This is where the Würzburg players come in: Professor Bernd Zimanowski and his team are known for simulating and analyzing eruptions and other volcanic processes in their physical-volcanological laboratory. That is why they were recruited by the Italian Civil Defense Authority, the National Geophysics and Volcanology Institute and researchers from the University of Bari for a joint project.

Artificial volcano explodes

Since 2005, scientists in the south of Italy, near Spinazzola in Puglia, are experimenting with a kind of artificial volcano: They fill a cannon with up to 300 kilograms of volcanic ash from Vesuvius and fire the cargo up to 40 meters high with precisely defined launching energy, This creates an eruption cloud in small format. display

This arrangement simulates the key aspects of a true volcanic eruption, scientists reported in the April Journal of Geophysical Research. The deposits of the artificial eruption cloud correspond to those in natural conditions. The magnitude of the experiment is sufficient to extrapolate to the conditions of real volcanoes.

For the sake of simplicity, the researchers did the first experiments with cold volcanic ash. In a real eruption, however, the material is of course hot. To simulate this, much more effort is needed: "The thermal conductivity of the ash is very poor. If you wanted to heat 300 kilos of it to 300 degrees, you would need several days to do that, "explains Zimanowski. Therefore, the scientists reduced their experiment and used a smaller cannon, which they filled with only 30 kilograms of hot ash. Such an amount could be heated in an electric oven overnight.

First hei e eruptions

After the first "hot eruptions", it is clear that the volcano specialists will probably be able to save on heating up in the future: "As far as the time of the collapse of the eruption cloud is concerned, the temperature does not matter the conditions as in the first experiments with cold ashes, "says Zimanowski. Now it is necessary to evaluate whether the flow velocity of the artificial pyroclastic flow is identical.

"If so, we can do our further experiments less with the cold ashes, " says the Würzburg researcher. The next work plan - presumably early 2008 - is the exact physical measurement of the artificial pyroclastic flows. With sensor fields that are created in the vicinity of the artificial volcanoes, then, among other things, pressure and temperature are to be registered.

"The first directly usable information for the civil defense authorities could result from this, " said the Würzburg professor. In the best case, the project concludes that buildings can be structurally protected against pyroclastic flows. In the environment of Mount Vesuvius there would be enough demand.

(idw - University W rzburg, 12.06.2007 - DLO)