known eruptions at the volcano have had a Volcanic Explosivity Index (VEI) of 3. Despite its activity, Sangay is located in a remote, uninhabited region; only a large Plinian eruption could threaten occupied areas to its west. Nonetheless, a flank collapse on its eastern side, possible given the volcano's construction and history, could displace nearby forest and possibly affect settlements. Access to the volcano is difficult, as its current eruptive state constantly peppers the massif with molten rock and other ejecta. For these reasons it is not nearly as well-studied as other, similarly active volcanoes in the Andes and elsewhere; the first detailed study of the volcano was not published until 1999. Ecology Sangay is one of two active volcanoes in the Sangay National Park, the other being Tungurahua to the north. As such it has been listed as a UNESCO World Heritage Site since 1983. The area's isolation has allowed it to maintain a pristine ecology relatively untouched by human interaction, and the park hosts a biome ranging from alpine glaciers on the volcanoes' peaks to tropical forest on their flanks. Altitude and rainfall are the most significant local factors affecting fauna, and therefore the lushest ecosystems are found on the wetter parts of the volcano's eastern slope. The highest level below the snowline is dominated by lichen and bryophytes. Below this lies a zone of small trees and shrubs which develops into montane forest, principally in western valleys and on well-irrigated eastern slopes, which occurs below . Tree heights develop from near the top to up to below ; below , subtropical rainforest is present, with temperatures between and up to of rainfall. Fauna is similarly distributed, with distinct altitudinal zonation present. The highest altitudes support the endangered mountain tapir, cougar, guinea pig, and Andean fox. Lower down, the spectacled bear, jaguar, ocelot, margay, white-tailed deer, brocket deers, northern pudú, and endangered giant otter can all be found. Bird species common in the area include the Andean condor, Andean cock-of-the-rock, giant hummingbird, torrent duck, king vulture, and swallow-tailed kite. Recreation Sangay can and has been climbed. It was first ascended in 1929 by Robert T. Moore, prior to its current eruption beginning in 1934. However, the volcano's current active state presents dangers to mountaineers in the form of falling ejecta; in 1976, two members of an expedition on the volcano were struck and killed by falling debris. In