The Sangay is a continuously active stratovolcano located in the Republic of Ecuador. It is the most southern and most active volcano in the country, and is known for its explosive expression which is manifested by thick clouds of ash, which have formed a kind of vault since 1976. Sangay comes from Samkay, an indigenous term meaning to frighten. The natives, however, witnessed violent explosions of this volcano to which they baptized thus, these explosions produced at least two boilers millennia ago and then erected the present building. This turbulent past was confirmed by some geological studies of this volcano. At the top are three large craters that erupt intermittently, there are also several cracks in this crater where volcanic lava flows generally. The central crater has a diameter of 100m and a depth of 50m to the northeast another crater with a diameter of 50m and a third to the west of the main crater. It is located in the eastern region 45 km southeast of Riobamba. This volcano is composed mainly of andesites and basaltic andesites. The deposits are made up of olivine, magnesian, augite, hyperstone and plagioclase. There are documented falls of rocks, pyroclastic flows, emission of lava, columns of ash and gases. Seismic activity is frequent. In past days large lahares traveled around the cone and the natural drainage has changed because of it numerous times. This volcano is solitary almost inside the forest, nearby populations are scarce, presents no greater danger.