Iztaccíhuatl

Iztaccíhuatl was built by many eruptions, over a very long time.

It has domes, cones and old lava flows.

The Complutense group explains that the Izta-Popo range began forming between the Pliocene and Quaternary periods, from andesite, dacite and rhyolite rocks lined up north to south.

Iztaccíhuatl grew through several stages of building up and breaking down, leaving cones, domes and lava flows. Most of it formed in the late Pleistocene, about 900,000 to 80,000 years ago. The youngest lava flows, at its southern end, are from the Holocene, the most recent part of Earth's history.

UCM: a Plio-Quaternary volcanic range of mainly andesitic, dacitic and rhyolitic deposits aligned roughly north-south. Iztaccíhuatl formed in several stages of construction and destruction, producing cones, domes, lava flows and volcano-sedimentary deposits, with intercalated pyroclastic tuffs and ash; its age is about 0.9 to 0.08 million years (late Pleistocene).

The most recent materials, andesitic-dacitic lava flows at the south-southeast end, are Holocene. Deep gorges and canyons cut both volcanoes and have channeled large hydrovolcanic flows.

A glacier called Ayoloco used to sit on this volcano. By 2018 it was gone.

Scientists put up a sign to remember it.

UN News reports that in 2018, satellite images and aerial photos showed scientists from Mexico's National Autonomous University (UNAM) that there was no more ice to monitor at the Ayoloco glacier. In 2021 they climbed the volcano and placed a plaque at 4,626 meters, where the glacier had been.

UNAM researcher Hugo Delgado Granados says the glaciers have been shrinking fast since the 1980s. Eight of the volcano's eleven glacier masses are gone.

UN News (5 June 2021): UNAM scientists found in 2018 that the Ayoloco glacier, which flowed west and could be seen from Mexico City, no longer existed; in April 2021 they placed a plaque at 4,626 m stating that it retreated until it disappeared in 2018.

Delgado Granados (UNAM Institute of Geophysics): rapid loss since the 1980s; a glacier is declared extinct when it stops behaving as glacier ice, even if some ice remains; global warming has extinguished eight of eleven glacier masses, and the three remaining are very vulnerable.

Ice on the volcano melts slowly and gives water to lakes and people.

The Ayoloco glacier used to give water to lagoons and people.

UN News explains that glaciers matter both for nearby communities and for nature. Their meltwater runs into lagoons and soaks into the ground, refilling underground water. Their pale ice also reflects sunlight and helps keep the climate cool.

The Ayoloco glacier fed the volcano's lagoons and, in dry times, gave water to people living in the area, in the municipality of Amecameca.

UN News: besides running into lagoons, glacier water infiltrates and recharges aquifers, and the light-colored ice reflects solar radiation and helps keep the climate cool. Ayoloco fed the volcano's lagoons and, in droughts, supplied water to residents of the area (municipality of Amecameca, State of Mexico).

UCM: the solid water reserves held on the slopes of Iztaccíhuatl and Popocatépetl are a necessary source for the surrounding population.

The air is thin high on this mountain. Climb slowly and rest.

Tell a grown-up if your head hurts.

Iztaccíhuatl's upper slopes are very high, and the air there is thin. The CDC says going up slowly gives the body time to adjust, and that children can get altitude sickness just like adults.

A headache is the main sign. The CDC says people with altitude sickness feel better quickly if they go down at least 300 meters.

CDC Yellow Book: ascend gradually (above 3,000 m, raise sleeping altitude by no more than 500 m a night); children are as susceptible as adults; headache is the cardinal symptom of acute mountain sickness, which improves rapidly with a descent of 300 m or more.

A mountaineer quoted by UN News recalls that her first climbs needed technical skill with crampons and, at times, an ice axe.