Above an elevation of , annual temperatures range from . There is no temperature data from Hualca Hualca, but data from
Chachani implies stable temperatures year-round. Annual precipitation is about , decreasing at lower elevations. During December–March, the
Intertropical Convergence Zone reaches the mountain and draws moisture from the
Amazon, as part of the
South American Summer Monsoon (
Pacific Ocean-derived moisture is trapped beneath a
temperature inversion at an elevation of and cannot reach Hualca Hualca). This is the
wet season, during which most of the annual precipitation falls. April to November is the
dry season. The mountain is snow-covered year-round. Precipitation on Hualca Hualca may constitute a source of
groundwater and recharge the hydrothermal system.
El Niño-Southern Oscillation events cause temperatures to increase and precipitation to decrease. Below an elevation of there is herbaceous vegetation, dominated by
Festuca and
Stipa but also featuring
cacti,
Peruvian feather grass and other
pioneer plant species. Above that altitude,
cushion plants such as
Azorella compacta replace the herbs until elevation, where most vegetation disappears except for
lichens and
mosses.
Peat bogs grow in valleys on the southern side of Hualca Hualca in places where precipitation water and
meltwater accumulate. They are classified as "
bofedales". Between elevations of , the land is used for
pasture of
alpaca,
cattle,
llama and
sheep. Animals include insects and birds like the
Andean condor. During the
Late Pleistocene, temperatures in the Peruvian Andes were up to lower, and episodes of increased precipitation led to the formation of giant lakes in the Altiplano ("
Lake Tauca") and (possibly) to the growth of glaciers. In recent decades,
temperatures have been increasing at a rate of about per decade. The warming has been blamed for the drying of springs and more irregular meltwater flows.
Glaciation Past glaciations have left
moraines down to altitudes of around the entire volcano. Moraine tongues form complex and well-preserved structures; they are particularly well-developed on the eastern flank of the volcano and in the Huayuray valley, where they reach lengths of and heights of . Other glacial
landforms are striated/polished surfaces,
glacial overdeepenings,
glacial valleys, inactive
cirques and outwash plains. During the
Last Glacial Maximum, the Ampato volcanoes featured an
ice cap with an area of about . The timing of glaciation in the Peruvian Andes is complex, with evidence of glacial advances at Hualca Hualca both during the last glacial maximum and the
"Tauca" and "Coipasa" periods. The advances produced several generations of moraines, and eroded older moraines.
Cosmogenic isotope dating has yielded ages of 17,000–16,000 and 12,000 years ago for glacial advances at Hualca Hualca, implying that glacier retreat at Hualca Hualca occurred later than at other Central Andean volcanoes. Final glacier retreat occurred at the beginning of the
Holocene; two advances in the Huayuray valley have been attributed to the
Little Ice Age. The moraines at Hualca Hualca have been used to reconstruct
equilibrium line altitude and temperature changes during the glaciation.
Glaciers persist around the summit in active cirques, and there is permanent snow cover on the subsidiary peaks. There are
crevasses and
seracs.
Rock glaciers occur in numerous locations around the mountain. The glaciers are
retreating; the Huayuray glacier lost half its surface area between 1955 and 2000 and a further near-halving occurred between 2000 and 2008; the Ampato volcanic complex might lose all of its glaciers by 2065, threatening water supplies in the region. == Eruption history ==