SATELLITE IMAGE ATLAS OF GLACIERS OF THE WORLD

GLACIERS OF SOUTH AMERICA--

GLACIERS OF ECUADOR

By EKKEHARD JORDAN¹ and STEFAN L. HASTENRATH²

Abstract

Even though Ecuador sits astride the Equator, 4 mountains in the Cordillera Occidental (Western Cordillera) and 13 mountains in the Cordillera Oriental (Eastern Cordillera) have summits that extend above the regional snowline and support more than 100 small glaciers. Ecuadorean glacier types include ice caps and outlet glaciers, small ice fields, and mountain glaciers on both volcanoes and nonvolcanic mountains. The total area of glaciers on the 17 volcanoes and other mountains is 97.21 square kilometers, 21.92 square kilometers in the Cordillera Occidental and 75.29 square kilometers in the Cordillera Oriental. Field surveys, photogrammetric analysis of vertical aerial photographs and Landsat images, and modern maps were used to calculate the total glacier area. The Cotopaxi stratovolcano, one of the highest active volcanoes on Earth at 5,911 meters, has an ice cap from which 23 outlet glaciers flow (total area of 19.09 square kilometers). Climatic conditions in Ecuador vary considerably, being influenced by the availability of moisture from either the Pacific Ocean or the Amazon basin, terrain elevation, and the orientation of mountain ranges. Glacierization is generally more developed on the eastern flanks of the cordilleras. A significant reduction in glacier area has been noted in Ecuador since the 1800's and apparently still continues.

Introduction

Ecuador's glaciers are situated close to the Equator in South America and thus can be considered to be among the best examples of continental tropical glaciation. The glaciers are restricted to the highest peaks in the Andes Mountains because of the proximity to the Equator and the prevailing climatic conditions. The individual peaks, mostly of volcanic origin, do not contain large contiguous ice fields, such as those found in Perú, Bolivia, Chile, and Argentina; instead, the glaciers occur as ice caps that feed numerous outlet glaciers and are confined to the limited summit areas. Table 1 provides information on the area and elevation of the small ice caps, outlet glaciers, small ice fields, and mountain glaciers.

The glaciers in Ecuador are located on the two chains of the Andes Mountains that flank the inter-Andean depression, the Cordillera Occidental and the Cordillera Oriental (fig. 1). The peaks range in elevation from around 4,000 m to more than 6,000 m. In the Cordillera Occidental, the four glacierized mountains are, proceeding from north to south, Cotacachi,³ Iliniza, Carihuairazo, and Chimborazo. In the Cordillera Oriental, the following 13 mountains are glacierized: Cayambe, Saraurcu, Antisana, Sincholagua, Cotopaxi, Quilindaña, Cerro Hermoso, Tungurahua, Altar, Cubillín, Sangay, Collay, and Cerro Ayapungo (Soroche). Contradictory information exists, however, in the literature regarding the presence of glaciers on Sangay and Cerro Ayapungo. Some references describe a partial glacier cover, and others mention only névé (perennial snow or firn) that persists for several years.

Table 1.--The glacierized areas of Ecuador

[Table 1 was compiled by Ekkehard Jordan from the following sources: field surveys in 1977 and 1980-1981; STEREOCORD interpretation of Cotopaxi (Jordan, 1983); official topographic map of Instituto Geográfico Militar, Quito, Ecuador; Hastenrath (1981); and satellite image interpretation using STEREOCORD (Jordan, 1984). Mountain type: IV, inactive volcano during the Holocene; AV, active volcano; and NVM, nonvolcanic mountain]

The total glacierized area in Ecuador is 97.21 km², 21.92 km² in the Cordillera Occidental and 75.29 km² in the Cordillera Oriental. The glacierization is more pronounced in the Cordillera Oriental because this eastern range is better exposed to the moisture supply from the Amazon basin. Also, glaciers are more abundant on the eastern, as opposed to the western, flanks of individual mountains.

Historical documentation of varying ice conditions in Ecuador is among the most numerous and continuous in all of the glacierized tropical areas (Hastenrath, 1981). The earliest reference to the glacierization of the Ecuadorean Andes dates back to the era of Spanish colonization in the 1500's. A geodetic expedition of the French Academy made observations in the middle 1700's. Von Humboldt visited the country in 1802, and geographic information from a variety of travelers remains abundant to the beginning of the 20th century. Recent surveys of ice conditions in Ecuador include those of Mercer (1967) and Hastenrath (1981). These varied sources indicate a rather extensive glacierization from the 1500's to the first part of the 1800's, followed by a drastic ice recession starting around the middle of the past century and continuing to the present time (Hastenrath, 1981). Heine's (1995) studies of moraines in Ecuador documented the historical recession of its glaciers, a global phenomenon of mountain glaciers during the 20th century. Clapperton's (1993) studies of late Pleistocene to early Holocene moraines in the Andes Mountains indicate an advance of glaciers and a lowering of the equilibrium line altitude by 300 to 400 m in the northern and north-central part of the Andes Mountains.

Figure 1.--Ecuador's Andean region at a scale of 1:2,000,000 showing glacierized areas characterized by volcano type, topography, and precipitation distribution. The map is based on (1) the Atlas Geográfico de la República del Ecuador (Instituto Geográfico Militar, 1978?), (2) official maps of the Instituto Geográfico Militar, and (3) fieldwork by the author (Ekkehard Jordan) in 1977, 1980, and 1981.

Manuscript approved for publication 18 March 1998.

¹ Lehrstuhl für Physische Geographie, Heinrich-Heine-Universität, Universitätstrasse 1, 40225 Düsseldorf, Germany.
² Department of Atmospheric and Oceanic Sciences, University of Wisconsin, 1225 West Dayton Street, Madison, WI 53706, U.S.A.
³ The names in this section conform to the usage authorized by the U.S. Board on Geographic Names in its Gazetteer of Ecuador (U.S. Board on Geographic Names, 1987). The names not listed in the gazetteer are shown in italics.