“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,” says scientist and and volcano adventurer John Search.
Just look at its activity during the past 50 years (excerpts from volcanolive.com):
2012 Activity
15 July 2012. Ash emission reached a height of 1 km above the crater, and ashfall occurred at Jurang Jero and Srumbung.2010-11 Largest Eruption in 100 years
Ash emissions reached an altitude of 40,000 ft, and 370,000 people were evacuated from a 20 km radius danger zone. Over 190 people were killed by pyroclastic flows and ashfall.2006 Eruptions
Seismic activity began increasing in March 2006, and 10,000 residents were prepared for evacuation…. On 8th June, the lava-dome growth rate was an estimated 100,000 cubic meters per day, with an estimated volume of 4 million cubic meters. Pyroclastic flows and rockfalls decreased in frequency and intensity after 28th June 2006.2006 Earthquakes kill 5,750 people
On 27th May 2006 a magnitude 6.3 earthquake killed about 5,400 people produced in a three-fold increase in activity at Merapi volcano. On 17th July 2006 a magnitude 7.7 earthquake produced an 8 m high tsunami which hit the southern coast of Java. The earthquake caused 5,750 deaths, 38,560 injuries, and up to 600,000 people displaced in the Bantul-Yogyakarta area.2001 Eruption
A major eruption began at Merapi volcano on 10th February 2001.1998 Eruptions
Between 11-19 July, 128 nuées ardentes occurred, including a strong pyroclastic ash and block flow at 1500 on 19th July.1994 Eruptions
On 22nd November 1994, a large number of dome-collapse nuees ardentes were generated over a period of several hours. The nuees ardentes descended mainly the Boyong valley and the Bedog valley, a tributary of the Krasak-Kecil valley.1986-87 Eruptions
Lava dome formation at Merapi volcano the largest since 1973.1984 Eruption
On 15th June 1984 explosions at the lava dome produced pyroclastic flows which extended 7 km from the volcano, and ashfall 80 km NW.1968 Eruptions.
The number of avalanches from the lava tongue were 1432 in June, 1370 July, 329 August, and 12 in September. Renewed activity began in October 1968 with an increasing number of lava avalanches.1967 Eruptions
A lava dome extruded in April 1967 at the upper Batang River on the SW slope of Merapi volcano. The dome collapsed in October 1967.
http://volcanolive.com/merapi.html
Thanks to Tom O. for this link