It is often called by the Nahuatl name Xinantecatl which is usually translated as The Naked Lord, Señor Desnudo in Spanish, although other etymologies have been suggested such as "Lord of the Corn Stalks", Tzinacantecatl or Zinacantepec. Further evidence regarding the etymologies of this mountain has surfaced after many archeology discoveries in and around the area. It has been concluded that its correct etymology is Chicnauhtecatl meaning "nine lakes" as the top of the cone has various deep lakes.
Description
The volcano has a wide summitcaldera which is open to the east. The highest summit, the Pico del Fraile, is on the southwest side of the crater and the second highest, the Pico del Aguila, is on the northwest. There are two crater lakes on the floor of the basin at about, the larger Lago del Sol and the smaller, but deeper, Lago de la Luna. A road formerly ran into the caldera to the lakes, but is now gated 2 km before the lakes. From the southeast, Nevado de Toluca looks flat-topped, like shoulders without a head. A Nahuatl legend provides a mythical explanation.
Geology
It is believed that Nevado de Toluca may once have been as tall as Popocatépetl, until an enormous eruption nearly 25,000 years ago blasted the top of the cone off and reduced its height by as much as. The same eruption generated thick lahars, or mudflows, which coated the sides of the mountains. An eruption approximately 500 years later deposited layers of pumice on the mountain's east and northeast slopes. The last major eruption of Nevado de Toluca occurred about 10,500 years ago, as the volcano erupted a total estimated volume of 14 km3 for a VEI strength of 6. The eruption emplaced of pebble-sized pumice in the City of Toluca region and ~ of medium to fine sand in the Mexico City region. Distal lahar deposits derived from the Upper Toluca Pumice event incorporated mammoth bones and other mammals in the basin of Mexico. The volcano became inactive after a volcanic plug formed in the volcano's vent. The plug eventually became known as El Ombligo.
Climate
Near the summit, Nevado de Toluca has a coldalpine climate with cold temperatures year round. There is little variation in the temperatures and frost and snow can occur in any month. The dry season covers from November to March and precipitation is low, averaging in March, the driest month. Temperatures during this time are cold, averaging in January. The wet season spans from May to October and precipitation is very high, averaging in July. The summit is often foggy, averaging 110 days with fog, most of it during the rainy season. The wettest record month was July 2008 when of precipitation fell and the wettest recorded day was July 16, 1999 when of precipitation fell. The highest temperature ever recorded was on August 16, 1993 and the lowest temperature recorded was on February 2, 2004.
Archeological sites
There are 18 registered archeological sites in the park, as this was a ritual center during pre-Hispanic periods. Bernardino de Sahagún wrote about the lakes as a place where the indigenous held ceremonies and sacrifices. The lakes themselves are considered to be two sites, as a large number of offerings, especially copal, were deposited in the lakes. These deposits can be found all over the lakebed as the burning copal was set adrift on the lakes’ waters until it sank. Other objects have been found such as ceramics and sculpted stones. Divers used to sack many of the pieces found here but now authorities carefully monitor those who dive. Most of the other sites are found on the crater's walls and peaks. One of the sites is called Xicotepec which is at the top of a rocky dome known as the Cerro de Ombligo. Principally green obsidian blades and multicolored ceramic has been found here. On the north side of the crater is Pico Sahagun, with ceramic pieces, Picos Heilprin North and South in which various types of objects have been found, and El Mirador, which is thought to be related the marking of the zenith of the sun. A stele found here seems to indicate this. The site at the highest altitude is Pico Noreste at 4,130 meters above sea level. It is a small platform with drainage on which has been found highly deteriorated ceramic pieces. On the west side is the Cerro Prieto Cave, which is really a rock shelter which is more than 60 meters high. Not only does it contain evidence of pre-Hispanic visits but also has been a shrine to the Archangel Michael since the colonial period. There have been intermittent archeological excavations here with the most recent occurring in 2010 sponsored by INAH which found artifacts dating from the Epi-Classic and Post-Classic periods and showed that the crater was a meeting place for astronomerpriests to predict the growing season.
