the municipality is flat. Heading west, the land begins to rise gradually in the middle of the territory, then the altitude increases sharply on the west end, as it is the foot of the Iztaccíhuatl volcano. Near this volcano, there are a number of other elevations such as Ocotepec, Tepechichipa and Zacatalatla. The steepness of the Iztaccíhuatl volcano makes it prone to rockslides as snowmelt runs down the side, especially from a depression on the side where snow tends to accumulate, called Ayolócotl. Visible along various areas of the volcano are areas devoid of vegetation where rockslides have violently disrupted the ecology. The municipality belongs to the upper basin of the Atoyac River, one of the most important basins of the state, where the river begins at the border between Mexico State and Puebla on the east side of the Sierra Nevada. Rivers and streams generally cross the area from southwest to northwest, coming from the Sierra Nevada, and all are tributaries of the Atoyac. These include the San Diego, Cuaxupila, Pipinahuac, Alseseca, Achipitzil, Tolimpa, Losa Cipreses, Actiopa, and Xopanac. Some of these rivers and streams have suffered reduced water flow due to deforestation. Today the Xopana River is mostly dry, and filled with garbage in places. Some of the rivers have cut deep ravines and small canyons into the landscape, including the La Manga, Xeniqui, Ocoxaltepec, Xacatiotlapa, Hueyatitla, Tepetla, Coxocoaco, Apitzato, and Hueacaclán. The snowmelt of the volcanos feeds most of these streams and rivers, and water and snow stored in depressions on the mountain allow for river flow during the dry season. In addition, rain and snowmelt feed underground aquifers and freshwater springs. The climate of the municipality divides into three zones. The lower valley areas have a temperate semi-humid climate with rains in the summer. A somewhat cold and semi-humid climate with rains in the summer predominates at the foothills of the Sierra Nevada. On the upper slopes of the volcano, the climate is cold. Similarly, vegetation divides into three zones. The low flat areas are all given over to farmland and urban areas. The foothills area is generally characterized by forests of pine, holm oak, and oyamel, with areas of brush land, but much of this area is being deforested and converted into new farmland. The upper slopes of Iztaccíhuatl are characterized by snowy rocky land with areas of alpine meadow. The municipality The small city