Toluca Valley
[1] The valley runs north–south for about 35 km (22 mi), surrounded by mountains, the most imposing of which is the Nevado de Toluca Volcano.
Mountains sides have tertiary volcanic rock, mostly basalt and andesite along with pyroclastic matter and breaches.
[4][5] The valley covers an area of about 700 square kilometres, running north south with a length of 35 km.
Its northern border is marked by the Guadalupana Volcano, the Cerro el Aguila and the Sierra Monte Alto.
[4] These mountains, along with the elevation of the valley in general cause the area to experience cooler temperatures than the rest of the region.
The Nevado is the fourth highest mountain in Mexico at 4,600 m asl, formed by successive eruptions with deposited layers of igneous materials.
[6] The mountain has important effects on the climate and hydrology of the Toluca Valley The piedmont is characterized by hills covered by broadleaf forests.
[7] Today, most of the state's population is still on the fringes of the Mexico City metropolitan area, but the second highest concentration of people is in the Toluca Valley.
[5] Due to the political shift, the Nevado de Toluca volcano which towers over the valley has become the cultural symbol for the State of Mexico.
[6] Until the mid 20th century, the main economic activities were agriculture and forestry, due to large expanses of forest, the valley floors’ fertile soils and the Lerma River.
The Nevado de Toluca park, despite its status as a federal reserve has lost half its trees since its establishment, mostly due to illegal logging.
Urban growth has been chaotic with no planned system of roads or of public transport resulting in traffic jams, especially in Toluca.
[5] The loss of water has led to the disappearance of the shallow lakes and wetlands that line the Lerma River in areas such as Almoloya del Río with has destroyed entire aquatic ecosystems.
[4] The Lerma River and other channels have been used as drainage channels so the pollution level is very high, surpassing governmental standards for “water suitable for recreational use, conservation of flora and fauna and industrial uses.” Concentrations of heavy metals are a significant problem in the Lerma River above the Alzate Dam.
By the late 15th century, it was a powerful city state that controlled much of the Toluca Valley and was the main target of Aztec conquest.
[2] In the Post Classic period (900-1519 CE), the valley was a complex linguistic mosaic with speakers of at least four languages, Matlatzinca, Mazahua, Otomi, and Nahuatl .
Five towns in the valley are mentioned more than once in native histories: Cuahuacan, Malinalco, Matlazinco, Teotenanco, and Xilotepec, indicating that they were important settlements from well before the Aztec conquest.
Toluca Valley town names begin to appear in Aztec records, and Matlatzinco was renamed as Calixtlahuaca.
In 1476 or 1477, the Aztecs confronted the Purépecha armies on the western edge of the Toluca Valley but were decisively defeated.
Tenochtitlan administered this area more directly than other parts of the Empire, with client states created on the Purépecha border.
There was some repression of rebellions under later emperor Ahuitzotl, but there was no major military activity in the valley again until the Spanish conquest .
[6] The area also has significant colonial architecture, particularly hacienda houses, churches and former monasteries; and mansions of the Porfirio Díaz era.
[5] The Toluca Valley is recognized by plant pathologists as the center of origin of potato late blight pathogen, Phytophthora infestans.
