Relief
The relief is characterized by being very rugged and hosting multiple volcanoes. The Mexican territory is formed by the Mexican Plateau, a wide plateau that is framed by the mountain ranges of the Sierra Madre Oriental and the Sierra Madre Occidental [13] . The Sierra Madre Occidental ends in Nayarit, at the confluence with the Neovolcanic Axis. From there, parallel to the Pacific coast, runs the Sierra Madre del Sur.
The Neovolcanic Axis crosses the territory from west to east, until it joins the Sierra Madre Oriental in the Mixtec Shield or Zempoaltépetl (at 3,395 meters above sea level). In the Neovolcanic Axis, of great volcanic activity as its name indicates, the highest peaks in Mexico are located [14] : the Pico de Orizaba or Citlaltépetl (5,610 m), the Popocatépetl (5,462 m), the Iztaccíhuatl (5,286 m), the Nevado de Toluca (4,690 m) La Malinche (4,461 m) and the Nevado de Colima (4,340 m). The birth of Paricutín, the youngest volcano in the world, took place in this geological province.
The extensions to the southeast of the Sierra Madre Oriental are known as Sierra Madre de Oaxaca or de Juárez, which ends with the Sierra Madre del Sur on the Isthmus of Tehuantepec. To the east of this region lie the Mesa Central de Chiapasand the Sierra Madre de Chiapas, which has its culminating point in the Tacaná volcano (4,117 m).
The most visible geographical features of the Mexican territory are the Baja California peninsula, in the northwest, and the Yucatan peninsula, to the east. The first is traversed from north to south by a mountain range called Sierra de Baja California, Sierra de San Francisco or La Giganta. Its highest point is the Three Virgins volcano (2,054 m). The Yucatan Peninsula, by contrast, is an almost completely flat limestone platform.
Located between the Madre Oriental and Occidental mountain ranges, and the Neovolcanic Axis, is the Mexican Plateau, which in turn is divided into two parts by small mountain ranges such as Zacatecas and San Luis. The northern part is drier and lower than the southern part. In it the Chihuahuan desert and the Zacatecas semi-desert are located. To the south of the transversal mountains is the fertile region of the Bajío and numerous valleys of cold or temperate land, such as the Tarasca Plateau, the valleys of Toluca, Mexico, and the Poblano-Tlaxcalteca. Most of the Mexican population is concentrated in this southern half of the highlands.
Between the Neovolcanic Axis and the Sierra Madre del Sur is located the Balsas Depression and the Tierra Caliente of Michoacán, Jalisco and Guerrero. To the east, crossing the intricate Sierra Mixteca, are the Central Valleys of Oaxaca, surrounded by steep mountains that complicate access and communications.
Climate
According to Bridgat, Mexico is a country with great climatic diversity. The geographical situation of the country places it in two well differentiated areas, separated by the Tropic of Cancer. This parallel would separate the country into a tropical and a temperate zone. However, the relief and presence of the oceans greatly influence the configuration of the map of climates in the country. Therefore, the country has a great diversity of climates, which in a very general way can be classified, according to their temperature, as warm and temperate; and according to the humidity existing in the environment, in: humid, sub-humid and very dry.
The dry climate is found in most of the center and north of the country, a region that comprises 28.3% of the national territory; it is characterized by the circulation of the winds, which causes little cloud cover and rainfall of 300 to 600 mm per year, with average temperatures of 22 ° to 26 ° C in some regions, and in others from 18 ° to 22 ° C [15 ] .
The very dry climate registers temperatures on average of 18 ° to 22 ° C, with extreme cases of more than 26 ° C; presenting annual rainfall of 100 to 300 mm on average, it is found in 20.8% of the country [15] .
In relation to the warm climate, it is subdivided into warm humid and warm sub-humid. The first of them occupies 4.7% of the national territory and is characterized by having an average annual temperature between 22 ° and 26 ° C and annual rainfall of 2,000 to 4,000 mm. For its part, the warm subhumid climate is found in 23% of the country; there are registered rainfall between 1,000 and 2,000 mm per year and temperatures ranging from 22 ° to 26 °, with regions where they exceed 26 ° C [15] .
Finally, the temperate climate is divided into humid and sub-humid; In the first one, temperatures between 18 ° and 22 ° C and rainfall averaging 2,000 to 4,000 mm per year are recorded; it comprises 2.7% of the national territory. Regarding the subhumid temperate climate, it is found in 20.5% of the country, it mostly observes temperatures between 10 ° and 18 ° C and from 18 ° to 22 ° C, however in some regions it can decrease to less than 10 ° C; registers rainfall of 600 to 1,000 mm on average during the year [15] .
The wet season extends between the months of May and October. On average it rains for 70 days a year. The dominant trend, however, is the scarcity of rain in most of the territory, a fact related to the obstacles posed to rain clouds by the high mountains that frame the Mexican Plateau. The average temperature for the country is about 19 ° C. However, Mexico City presents its extreme averages in the months of January (12 ° C) and July (16.1 ° C). In contrast to Ciudad Juárez, Mexicali, Culiacán, San Luis Potosí, Hermosillo, Nuevo Laredo, Torreón, Saltillo and Monterrey where the temperatures are really extreme.
