El Misti in Peru, as seen from Arequipa.
As I like to remind people concerning volcanic hazards, an ounce of prevention is worth a pound of the cure. This is not to imply we can prevent volcanic hazards from affecting us, but rather that proper mitigation in the form of monitoring, planning, education and practice can save countless lives (and dollars) when a volcano erupts. Officials in Peru seem to believe this, as they recently ran for practice evacuations for residents around El Misti, in the southern part of the country. Jersy Mariño from the Instituto Geológico, Minero y Metalúrgico (INGEMMET) says that upwards of 100,000 people living around the volcano (in spanish) could be in harms' way when El Misti erupts again. So, officials and residents have taken part in evacuation drills to be able to (a) know what to do if a real evacuation is needed and (b) find deficiencies in the current mitigation plan. This goes with the recent volcanic hazards map prepared for the volcano.
El Misti last erupted in 1985 and tends to produce explosive eruptions and pyroclastic flows. Most eruptions are in the VEI 1-2 range, although an eruption ~80 B.C. is believed to be closer to a VEI 4, suggesting that El Misti is clearly capable of large eruptive events. The danger El Misti poses is amplified by the fact that the city of Arequipa, population of over 1,000,000, is only 17 km / 10.5 miles from the summit of the volcano. Just looking at the topography around the volcano shows that most large flows - pyroclastic or lahars - will be funneled towards the greater Arequipa area. The more that can be done to prepare the area for El Misti's next eruption, the less likely a true disaster might occur.
