Merapi volcano is one of the world's most active and dangerous volcanoes. It contains an active lava dome which regularly produces pyroclastic flows. Eruptions occur at intervals of 1-5 years and are of low gas pressure. Since magma is poor in gas, eruptions are usually less than VEI 3 in size.

Merapi is one of the most active volcanoes in Indonesia and has produced more pyroclastic flows than any other volcano in the world. It  has been active for 10,000 years. 

Most eruptions of Merapi involve a collapse of the lava dome creating pyroclastic flows which travel 6 to 7 km from the summit. Some awan panas have traveled as far as 13 km from the summit, such as the deposit generated during the 1969 eruption. Velocity of pyroclastic flows can reach up to 110 km/hour. A slow up flow of andesitic magma leads to an extrusion of viscous magma, which accumulate and construct a dome in the crater.