Almost all Africa is in tropical and subtropical climate zones. Its glaciers are found only in two isolated ranges and the Ruwenzori Range. Kilimanjaro, at , is the highest peak on the continent. From 1912 to 2006 the glacier cover on the summit of Kilimanjaro apparently retreated 75%, and the volume of glacial ice decreased 80% from its 1912 value due to both retreat and thinning. In the 14-year period from 1984 to 1998, one section of the glacier atop the mountain receded . A 2002 study determined that were conditions to continue, the glaciers atop Kilimanjaro would disappear sometime between 2015 and 2020. A March 2005 report indicated that almost no glacial ice remained on the mountain, and the paper noted this as the first time in 11,000 years that barren ground had been exposed on portions of the summit. Researchers reported Kilimanjaro's glacier retreat was due to a combination of increased sublimation and decreased snow fall.