The VSI report for 9-15 January noted that activity increased at Merapi, prompting the hazard status to be raised to Alert Level 3 at 0600 on 10 January. Observers frequently noted a weak white plume that rose 500 m above the summit. Glowing lava avalanches continued into the upstream areas of the Sat, Lamat, and Senowo rivers to a runout distance of 2,000 m. On 14 January there were 29 pyroclastic-flow events, which filled the Sat, Lamat, and Senowo rivers out to a maximum distance of ~4,000 m. During this week there were continuous glowing lava avalanches and pyroclastic flows at intervals of 30-60 minutes. The Associated Press reported on 11 January that authorities had ordered people living around the mountain to be on high alert and prepare to leave at short notice.

Geological Summary. Merapi, one of Indonesia's most active volcanoes, lies in one of the world's most densely populated areas and dominates the landscape immediately north of the major city of Yogyakarta. It is the youngest and southernmost of a volcanic chain extending NNW to Ungaran volcano. Growth of Old Merapi during the Pleistocene ended with major edifice collapse perhaps about 2,000 years ago, leaving a large arcuate scarp cutting the eroded older Batulawang volcano. Subsequent growth of the steep-sided Young Merapi edifice, its upper part unvegetated due to frequent activity, began SW of the earlier collapse scarp. Pyroclastic flows and lahars accompanying growth and collapse of the steep-sided active summit lava dome have devastated cultivated lands on the western-to-southern flanks and caused many fatalities.

Sources: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM), Associated Press