 A study by glaciologists of two small glaciers in South America reveals another retreat . More than 80 % of all glacial ice in the northern Andes is concentrated on the highest peaks in small plains of approximately 1 km2 ( 0 @.@ 39 sq mi ) in size . A 1992 to 1998 observation of the Chacaltaya Glacier in Bolivia and Antizana Glacier in Ecuador indicate that between 0 @.@ 6 m ( 2 @.@ 0 ft ) and 1 @.@ 9 m ( 6 @.@ 2 ft ) of ice was lost per year on each glacier . Figures for Chacaltaya show a loss of 67 % of its volume and 40 % of its thickness over the same period . Chacaltaya Glacier has lost 90 % of its mass since 1940 and is expected to disappear altogether sometime between 2010 and 2015 . Antizana is also reported to have lost 40 % of its surface area between 1979 and 2007 . Research also indicates that since the mid @-@ 1980s , the rate of retreat for both of these glaciers has been increasing . In Colombia , the glaciers atop Nevado del Ruiz have lost more than half their area in the last 40 years . Further south in Peru , the Andes are at a higher altitude overall , and there are approximately 722 glaciers covering an area of 723 km2 ( 279 sq mi ) . 
