Polish climbers in 1937 first observed this activity, below the summit and in the summit crater. Fumarolic activity appears to be linked to a rift structure on the volcano. Climbers in 1957 reported that the fumaroles were noisy and the emissions intense enough that with unfavourable winds they could suffocate people. The fumaroles can be observed from satellites in the form of temperature anomalies which reach above background temperatures, but the steam plumes are poorly visible from the ground except from close distance. The occurrence of geysers in the summit region has been reported. Human history As Ojos del Salado is hidden behind and nested among many peaks of similar elevation, for centuries travellers and mountaineers paid little attention to the mountain. Its remoteness meant that for a long time, both its elevation and exact topography were unclear. The positions and names of the mountains were frequently confused. The Inca used the Paso San Francisco as a major crossing of the Andes but there is no evidence of them building any archeological sites on Ojos del Salado even though a number of such sites exist in the surrounding region. The Spanish conquistador Diego de Almagro crossed the Andes at Ojos del Salado but did not mention it. Ojos del Salado is likewise absent from the 1861 plans of William Wheelwright for a railway across Paso San Francisco. The explorer Walter Penck crossed the area in 1912/13 and 1913/14 but did not identify the mountain. Ascents and debate on elevation In 1896, 1897 and 1903 the Chile-Argentina boundary commission identified a peak in the area and named it "Ojos del Salado"; according to a myth their "Ojos del Salado" was a much smaller mountain and the actual Ojos del Salado was their "Peak 'e'". The Polish climbers Justin Wojsznis, Stefan Osiecki, Witold Paryski, Jan Szczepański reached the summit on February 26, 1937 and left a cairn but most of the maps and report they drafted were lost during World War II. After the Polish expedition, the mountain remained unclimbed, although expeditions went to its lower slopes and sometimes confused other peaks for Ojos del Salado until 1955. In that year an expedition from Tucumán ascended a mountain south of Ojos del Salado, which they mistook for the volcano. They stated that the peak may be higher than Aconcagua, which media reported as if it were proven fact. These measurements set off