daily tours. 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. In recent years, trekking tours on the ice have gained popularity. The two standard tours are a "mini-trekking" option, consisting of a short walk of about an hour and a half, and a "big ice" version, which is usually about five hours. Tour companies generally provide crampons to customers. As the Zone closes to the public during the night - after 8 pm - on some occasions the ice bridge collapses without spectators, as happened in the event of March 11, 2018. Fauna A small glacier stonefly called Andiperla willinki inhabits the glacier. Also called "the pearl of the Andes" or "dragon of Patagonia" is a kind of plecoptera of the family Gripopterygidae that inhabits the Patagonian glaciers in Argentina and Chile, spending its entire life on the ice. It measures approximately and feeds on bacteria that live on the ice brought by the wind. It was found on the Upsala Glacier and described by Aubert Willink in 1956. Due to its rarity, small size, and extreme habitat, they believed it had become extinct. However, it was rediscovered in 2001 in a Torres del Paine glacier in a 20 m deep recess; on this occasion, it was named by the crew as "Patagonian dragon". References External links The Glaciers National Park Perito Moreno Glacier at NASA Earth Observatory, November 21, 2021 Pictures of Perito Moreno Glacier Glaciers of Argentina Glaciers of Chile World Heritage Sites in Argentina Landforms of Santa Cruz Province, Argentina First 100 IUGS Geological Heritage Sites