Eruptions readers have pointed out to me that El Reventador, one of the more active volcanoes in the Andes - that also happens to be close to Quito - has experienced some larger explosive eruptions in recent days. VAAC reports for the area mentioned that yesterday the volcano produced an ash plume that reached at least 4 km / 13,000 feet, while seismicity at the volcano suggests that similarly-sized explosions have rocked the edifice overnight and into today. However, cloud cover has made it difficult to see any of these events on satellite imagery. Reports from on the ground in Ecuador - specifically from the Geophysical Institute of the National Polytechnical University (IG) - mention intense seismicity related to these explosions and a plume that reached ~2 km / 6,500 feet. Some areas near El Reventador have experienced minor ash fall, but Quito and the main airport are unaffected so far by the new activity at the volcano.
El Reventador has had numerous eruptions over the last few decades, some of which have been impressive explosive eruptions - including a VEI 4 eruption in 2002 that dropped ash on Quito 95 km away and numerous VEI 3 events as well. You can check out some images of the 2002 activity here along with a NASA Earth Observatory shot of the tan plume towering over the clouds.
{Special thanks to the Eruptions readers who supplied links and info for this post.}
Top left: An undated image of El Reventador in Ecuador.