Peru’s El Misti volcano shaken by swarm of 224 quakes: last major eruption occurred 540 years ago

August 28, 2012 – PERU - Peruvian geologists have revealed that recent activity at El Misti signal that the volcano is active. Last Thursday researchers at the Geophysical Institute of Peru (IGP) found that El Misti – located 17 km outside the city of Arequipa – had recently recorded the highest amount of seismic activity than in the past five years. Engineer Orlando Macedo told El Comercio that 224 earthquakes were registered at El Misti – an event known as an earthquake swarm – and which signaled that the volcano was no longer dormant. El Misti, he said, experienced 143 volcano tectonic earthquakes, which were caused by the fracture of rock inside the volcano, due to sudden changes in pressure and temperature. Despite the recent increase in activity, the IGP said there were still no conditions for an eruption to occur at El Misti, which last erupted sometime between 1450 and 1470. For an eruption to happen, Macedo said, El Misti would have to experience continued earthquakes, which “would have to occur after long-term movements of magma, and causing these earthquakes known as tremors, with lava.” –Peru this week

US records show activity at the volcano in 1985 but Peruvian authorities said the volcano has been relatively dormant for nearly five centuries.