Mount Merapi, Indonesia’s most active volcano erupts (Video)

It is a phreatic eruption, which occurs when the magma heats earth or surface water. Slight tremors felt in the surrounding towns of Surakarta, Boyolali and Klaten. About 150 hikers are still on the volcano but they are safe.

Jakarta (AsiaNews) - A sudden eruption of Mount Merapi has been registered, the most active volcano in the country located on the border between the Central Java province and the special region of Yogyakarta. From 7.32 this morning an imposing cloud of ash has been rising into the sky and the authorities have ordered the evacuation of residents and tourists within five kilometers of the peak.

Experts from the National Disaster Mitigation Agency (BNPB) state that the Merapi is  undergoing a phreatic eruption that occurs when the magma heats ground or surface water. The extreme temperature of the magma (from 500 to 1,170 ° C) causes almost instantaneous evaporation of the water, with consequent explosion of steam, water, ash, rock and volcanic bombs. The phenomenon occurs without warning.

The eruption caused mild tremors, felt in the surrounding towns of Surakarta, Boyolali and Klaten. The Yogyakarta International Airport has been closed temporarily. Local media report that around 150 hikers are still on Merapi but they are safe. Sutopo Purwo Nugroho, spokesman for the BNPB, says: "We ask the population to remain calm. The alert level of the volcano remains normal, at level 1. We will continue to monitor the situation".