This is the conclusion reached by a German-British research group led by Dr. Danilo de Genova from the University of Bayreuth.
“For geology, it has always been a mystery what causes sudden and violent volcanic eruptions that look quite calm on the outside. But with the help of nano-geological research, we are now on the trail of explanation, says Dr. de Genova. “At the beginning of the chain of causes and effects that can end in disaster for people living near the volcano, there are very small grains of crystals with a high content of iron, silicon and aluminum.”
Due to their small size – tens of thousands of times less than the thickness of a human hair – these crystals are called “nanoliths”. Scientists found traces of them in the ash left by volcanic eruptions, and then, through careful research, were able to describe and show how they affect the properties of volcanic magma.
Dr. de Genova’s group focused on the study of magma with a low content of silicon oxide, which turns into basalt after eruption at the surface. Typically, such magma has a low viscosity and forms a very liquid and flowing lava. But, as it was possible to find out, the nanoliths contained in such magma, if their concentration is high enough, can increase its viscosity. As a result, magma starts to work like a plug, holding back the release of volcanic gases. The pressure in the volcano gradually increases, and as a result, a sudden explosion occurs.
“A constant, light plume of smoke over a volcano does not necessarily mean an impending dangerous eruption,” says de Genova. “On the contrary, an inactive and peaceful looking volcano may well be misleading.” The authors of the study suggest that this is exactly how – suddenly – Vesuvius exploded almost two thousand years ago, burying Pompeii, Herculaneum and Stabia, along with their inhabitants, under a layer of ash and pyroclastic deposits.