The Andean Glacier and Water Atlas

Venezuela In 1952, 10 glaciers could be found on the mountains of Venezuela (Schubert, 1998). A recent survey found only one remained, the Humboldt glacier (Braun and Bezada, 2013). The Humboldt glacier is located on the northwest-facing slope of Pico Humboldt, the second highest peak in Venezuela (4,942 m). In 2011 the glacier covered an area of approximately 0.1 km 2 and is predicted to disappear by 2021 (Braun and Bezada, 2013). Colombia In Colombia, dramatic glacier recession has taken place, mostly from the mid-1980s onward (Vuille et al., 2018). It is estimated that eight of Colombia’s tropical glaciers disappeared during the 20th century (Ceballos et al., 2006) and more have disappeared since the start of the 21th century (Poveda and Pineda, 2009). A 2016 examination of satellite data, over an area of approximately 42 km 2 of glacier extent, distributed over four mountain ranges, revealed a reduction of 38 per cent in glacier extent in the area since the 1990s (Rabatel et al., 2018). It is predicted that only the largest glaciers on the highest peaks will persist until the second half of this century. Remnant glaciers like Las Conejeras, that are being monitored with in situ measurements, are likely to disappear in the coming years (Rabatel et al., 2018).

Some of the remaining glaciers cap active volcanoes, which can be a deadly combination. The presence of snow and ice provide a source of water that can mix with erupted volcanic rock and avalanche material to form lahars, a post-eruption mix of meltwater and rock that usually flows down valleys (Vuille et al., 2018). Lahars can be more destructive than lava flows as they can travel at high speed. The lahars that formed following the eruption of Nevado del Ruiz in 1985 were the result of heating approximately 10 km 2 of the ice and snow and resulted in the death of more than 23,000 people (Pierson et al., 1990). Ecuador Ecuador’s glaciers are located closer to the equator than any other Andean glaciers. They are mostly found on mountain ranges of volcanic origin and are restricted to the highest peaks. Like those of Colombia, they occur as ice caps on summit areas and feed outlet glaciers (Jordan and Hastenrath, 1998). The glaciers are confined to two mountain chains, the Cordillera Occidental with 4 glaciers and the Cordillera Oriental with 3 glaciers. Glaciers are more common in the Cordillera Oriental because moist air from the Amazon increases precipitation in this region (Cáceres, 2010). The glaciers situated on the Antizana and Cotopaxi volcanoes are of particular interest because they contribute to the water supply of Ecuador’s capital city, Quito, where more than 2 million people live (Francou et al., 2000; Francou, 2004; Vergara et al., 2007). Mass loss from glaciers in this region has been substantial in recent decades and is expected to continue under climate change scenarios (Francou, 2004; Vuille et al., 2008). Aerial photographs of Antizana 15, show that the glacier retreated very rapidly between 1995 and 2000, a period that corresponded to strong El Niño events (Francou et al., 2000; Francou et al., 2004). The Cotopaxi glaciers have also been monitored and results indicate that they lost approximately 52 per cent of their surface area between 1976 and 2016 (Jordan et al., 2005; Cáceres, 2010; Cáceres 2016; Cáceres 2017). Glacier retreat on Chimborazo volcano has also been dramatic over the past few decades, with glaciers losing 72 per cent of their surface area between 1962 and 2016 (Cáceres, 2010; Cáceres, 2016; Cáceres, 2017). Peru The Peruvian Andes hosts the largest number of tropical glaciers in the world. The glacierized areas are found in 20 distinct cordilleras, extending from central northern Peru to the southern border (Morales Arnao, 1998). There are two major glacier systems, the largest of which, Cordillera Blanca, part of the Cordillera Occidental or western range, extends for 200 km in the central northern part of Peru. Eight of the largest glaciers in Peru are located in the Cordillera Blanca, which is the world’s most extensively glacier-covered tropical mountain range (Morales Arnao, 1998).

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