Volcanic activity is almost constant along the arc of islands that make up Indonesia. If you follow the news, every few weeks there is a report on another Indonesia volcano becoming restless enough that areas surrounding the volcano are deemed "off limits" or evacuations are needed. This week, it was increasing activity at Tangkubanparahu on Java that has people's attention. The volcano has produced a number of small-to-moderate explosive eruptions over the past day that resulted in a ~500 meter / 1,640 foot ash plume – enough noise to deem the entire summit crater area off limits to the frequent tourists who hike the mountain and to raise the alert status to its second highest level. Tangkubanparahu has a history of small (VEI 1-2) eruptions that are dominated by stream-driven explosions (phreatic) and based on the descriptions I've seen, this activity fits into that pattern. If the activity at the volcano were to increase, it is interesting to note that the city of Bandung (population 7.4 million) is only 15 km from Tangkubanparahu. Bandung is in quite an auspicious location, with no less than 11 volcanoes listed in the Global Volcanism Program database within 70 kilometers of the city.
If you want to catch up on all the volcanic activity worldwide for the past week, be sure to check out the latest Weekly Volcanic Activity Report from the USGS/Smithsonian GVP.