Cerro Negro de Mayasquer along the Colombia-Ecuador border, seen in September 2006. Photo by SGC. It appears that an ongoing volcanic crisis along the Colombia-Ecuador border is beginning to look more significant. A sharp increase in the number and size of earthquakes under Cerro Negro de Mayasquer and Chiles has prompted the evacuation of over 12,000 people as both countries prepare for a potential eruption. What kind of eruption is difficult to tell. The complex of volcanic vents has no confirmed historic eruption and the dates for the last eruption from each part of the volcanic complex are uncertain -- possibly in the last 10,000 for Cerro Negro and ~174,000 years ago for Cerro Chiles. However, volcano monitoring agencies on both sides of the border are taking the activity seriously. Over 4,300 earthquakes have occurred in the last 24 hours at Cerro Negro de Mayasquer and Chiles and a number of these earthquakes have been over M4 and felt as far away as Pasto and Quito. Most of the earthquakes have occurred at depths of only 3 to 5 kilometers beneath the volcanic complex. Combine this with continued deformation of Cerro Negro de Mayasquer and Chiles detected by instruments and it does seem that magma is rising underneath the volcanoes. Recent media reports also claim that local water sources have become contaminated by sulfur and iron, which, if proven true, could suggest abundant degassing of magma. The SGC in Colombia has placed Cerro Negro de Mayasquer and Chiles on its orange alert status. Without much recent eruptive record at Cerro Negro de Mayasquer and Chiles, it is hard to even speculate what kind of eruption might occur. Most of the youngest lava flows are andesite and dacite, which can also erupt explosively, so we might expect an eruption similar to those at Galeras or Reventador. Two countries will be watching how this activity progresses over the next few weeks.