Milpa Alta
From Wikipedia, the free encyclopedia
Milpa Alta is one of the 16 delegaciones (boroughs) into which Mexico's Federal District is divided. It is the second largest and most rural of all delegaciones.
In the July 2003 local election, Milpa Alta was the only delegación to elect a borough mayor from the Institutional Revolutionary Party.
[edit] Geography and Climate
Milpa Alta covers an area of 228 sq kilometers. It presents a heavily mountainous relief. It's lowest point, San Antonio Tecomitl, has an altitude of 2250 above sea level, ten meters above the median altitude for Mexico City. Surrounding Teuhtli volcano there is a strip of land slightly sloped that gradually becomes higher moving west. This region is known as the Milpa Alta valley, and in it most of the borough's population inhabits. The Milpa Alta valley rises up to 2700 meters above sea level, and it's climate is thus cooler than in the rest of the Mexico City basin. This little valley separates the Teuhtil volcano from the Ajusco-Chichunautzin mountains, that takes its name from its highest peaks.
The Ajusco-Chichinauhtzin mountains constitutes the highest region of the Federal District, with peaks above 3,500 meters above sea level (11,500 ft). This is then the highest region of the borough, and the tallest point is at the summit of Tlaloc volcano, with 3,690 meters above the level of the sea (12,992 ft). Along this mountain chain the following volcanos are placed: Cauhtzin, Chichinauhtzin, Tetzcacóatl, Acopiaxco, San Bartolo and Ocusacayo, all of which are above 3,100 masl (10,170 ft).
The Ajusco-Chichinauhtzin range emerged after violent volcanic activity during the cuaternarian period; in other words, this means that the surface of Milpa Alta is reasonably young in terms of geologic time. Before the emergence of this wall of mountains, the Valley of Mexico basin had natural drainage to the Balsas river. But the emergence of this mountain chain provoked that the basin became endorheic, which allowed the development of the lacustrine system of Texcoco, and contributed without doubt to the modification of the ecosystems south of the Federal District.
The entirety of the territory of Milpa Alta is part of the geologic subprovince of Lakes and Volcanoes of Anahuac, in turn corresponding to the province of the Nevolocanic Axis (Eje Neovolcánico). The topoforms included in the borough are the Sierra Volcanica with stratovolcanoes -more than 95% of the land area- and the basaltic tableland. This las one is only present in small portions to the East of the borough and a strip placed near the Cuahtzin and Teuhtli volcanoes.
As over 96% of Milpa Alta's surface is product of geologic activity of the cuaternarian, the greater part of its 230 km² is covered in some sort of volcanic rock, specially basalt (35% of the land surface) and tuff. Less than 2 km² of territory are covered by an alluvial soil type. The geologic zone of this characteristic is localised to the East of the Villa Milpa Alta, and is part of the same-named valley. To the north of the valley there is the Teuhtli volcano. This is the oldest part of the borough, as it emerged in the Tertiary period. It is a peculiar (and inactive) shield volcano with an ash cone, made up by Andesite.
The greater part of the Milpa Alta territory is placed in the Moctezuma river basin of the hidrologic region of río Pánuco. Over 60% of the borough belongs to this region; in turn, the rest belongs to the basin of the Grande de Amacuzac river, of the hidrologic region of Balsas. Nevertheless it doesn't possess any permanent flow of water due to the porous characteristic of its soils. In the rainy season, the mountain slopes are home to numerous brooks, of which the largest are Cuauhtzin, along the slopes of such mountain, and the Tlatixhuatanca, along the northern slope of Tlaloc volcano.
As altitude increases, the climate of Milpa Alta becomes cooler and wetter. The larger part of its territory, that is, the slopes of the mountain chain, have a semicold subhumid climate, with heavy summer rainfall (INEGI, 2002). This zone is practically uninhabited and covered by pine and fir forests. Other fraction of nearly 30% have a more temperate climate, with summer rains. It corresponds to the valley of Milpa Alta and the lower slopes of the mountains. This is where most of the population leaves and where the single most important economic activity of the borough takes place: the cultivation of nopal (cactus). In this region, the INEGI distinguishes to sections by the amount of precipitation. The Milpa Alta valley is slightly drier than the mountain slopes, but still remaining amongst the wettest parts of the Valley of Mexico. The coolest and wettest region of Milpa Alta is the summit of Chichinautzin and Tlaloc volcanoes. Rainfall is very high and the median temperature is 8°C (46°F). In turn Villa Milpa Alta's median temperature is 14°C (57°F). The following chart illustrates the region of San Ana, in the warmest part of the borough, with a median temperature of 15°C (59°F) and average rainfall of 725 mm (28.5 in).
| Climate chart for Santa Ana | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| J | F | M | A | M | J | J | A | S | O | N | D |
|
11
20
6
|
9
22
7
|
14
24
8
|
30
24
10
|
62
25
11
|
129
23
11
|
140
22
10
|
145
22
10
|
105
22
10
|
58
21
9
|
14
21
7
|
7
20
6
|
| temperatures in °C • precipitation totals in mm source: [1] |
|||||||||||
|
Imperial conversion
|
|||||||||||
[edit] External links
- (Spanish) Delegación Milpa Alta Official site
- (Spanish) Consejo de la Crónica de Milpa Alta Official site
