The 250 km2 ice formation, and 30 km in length, is one of 48 glaciers fed by the Southern Patagonian Ice Field located in the Andes system shared with Chile. This ice field is the world's third largest reserve of fresh water. The Perito Moreno glacier , located 78 kilometres from El Calafate, was named after the explorer Francisco Moreno, a pioneer who studied the region in the 19th century and played a major role in defending the territory of Argentina in the conflict surrounding the international border dispute with Chile. The Perito Moreno Glacier is one of only three Patagonian glaciers that is growing. The reason remains debated by glaciologists. The terminus of the Perito Moreno Glacier is 5 kilometers wide, with an average height of 74 meter or 240 ft above the surface of the water of Argentino Lake, in Argentina. It has a total ice depth of 170 meters or 558 ft. Due to its size and accessibility, Perito Moreno is one of the major tourist attractions in southern Patagonia. It is less than two hours by bus from El Calafate, and many tour companies run daily visits. A large visitor centre at the site features a walking circuit which allows visitors to view the southern flank and the east facing edge of the glacier.