Update on the June 3, 2018 eruption at Fuego volcano, Guatemala

There are at least 69 victims among the population, according to an unfortunately not definitive update, of the dramatic explosive eruption of Volcan de Fuego, in Guatemala, which took place on June 3, 2018.  
Fuego is a volcano that erupts magmas with andesitic-basaltic chemistry, which belongs to the Central American chain of volcanoes formed due to the sinking (subduction) of the Cocos plate under the North American one. Also for this reason, its eruptions are often explosive, especially due to the high water content in its magmas.
The analysis of the video-photographic material available on the internet (Source: Ansa) it does not yet allow a detailed reconstruction of the eruptive events of 3 June, also because at the time of the eruption the volcano was covered by a thick blanket of clouds. Nonetheless, it is possible to outline an initial dynamic on the basis of some observations.
An intense explosion produced the emission of a mixture of gases, ash, lapilli and lava fragments, perhaps also causing the simultaneous collapse of a lateral portion of the crater. Due to the high eruptive rate and the high density of the erupted material, this mixture formed a pyroclastic flow (sometimes also called avalanche or pyroclastic current, or burning cloud), which spread mainly towards the South, guided by the morphology of the flank of the volcano.
The pyroclastic flows generated by this type of explosive eruptions are typically characterized by a high speed (normally variable between 30 and 40 m/s, or 110-150 km/h), which makes them turbulent (i.e. whirling) and capable, therefore , to overcome important topographical reliefs, although they mainly spread along the valleys and basins dug on the slope of the volcano by water courses. These pyroclastic flows are capable of eroding the soil, increasing their volume and mixing with the water present in the soil. Their impact energy can be higher than that of a tornado and they are able to raze entire forests and inhabited centers to the ground in the areas closest to the eruptive vent. Even the most peripheral and distal regions reached by pyroclastic flows are extremely dangerous due to the high concentration of ash which prevents breathing.
The images of the eruption show some buildings in flames and burn marks on the victims and wounded. The temperature of pyroclastic flows is normally lower than that of the erupted magma, but often exceeds 400°C (burning of wood occurs between 260 and 315°C, while exposure to temperatures above 100°C for a few minutes is lethal for humans and animals).
The ashes, still incandescent, deposited by the pyroclastic flows, were subsequently mobilized by rainfall and surface waters, also generating lethal flows of boiling mud which, following the course of rivers and streams, overwhelmed the inhabited centers, causing further destruction and death . These are the so-called lahars, observable in various dramatic images of the eruption easily available on the internet.
The National Institute of Geophysics and Volcanology continues to follow and study the Vulcan de Fuego event of 3 June due to its extreme scientific and social interest, also for the purpose of mitigating the risk of Italian volcanoes.