In Ecuador, the Cotopaxi volcano rises to almost 5 900 meters in altitude. The glaciers that cover its crest are constantly being monitored : in the event of an eruption, their melting could cause devastating mudslides. Scientific expeditions conducted at such high altitude are a real challenge, especially for Arnaud Guérin, who suffers from acute mountain sickness. At the foot of the volcano, the Chagras move their cattle on horseback. If an eruption occurs, they can quickly evacuate their endangered herds. Santiago Benitez is a shaman who keeps the temazcal tradition alive. It is a very ancient spiritual practice that involves heating volcanic rocks.