Figure 4. A pyroclastic flow referred to Merapi type nuee ardente at 08:54:37 on 7 June 2006 traveling down Merapi’s upslope region in a generally SE direction. (The Research and Technology Development Agency for Volcanology-BPPTK, Yogyakarta).
On the basis of field studies and geochronological data, Camus et al (2000) divided its history into four periods: Ancient, Middle, Recent and Modern Merapi. The Ancient Period may have begun around 40.000 y BP and lasted until 14.000 y BP as the Middle Period begun. The Recent Period begun around 2200 y BP and was replaced by the Modern Period after the eruption of 1786. During the Middle Merapi stage, a St. Helens-type edifice collapse occurred. During the Recent Merapi stage, two violent magmatic to phreatomagmatic eruptions interrupted the growth of the volcano.