![Basin of Mexico 1519 map-en](https://upload.wikimedia.org/wikipedia/commons/9/99/Basin_of_Mexico_1519_map-en.svg)
The Valley of Mexico ( es, Valle de México) is a highlands
plateau
In geology and physical geography, a plateau (; ; ), also called a high plain or a tableland, is an area of a highland consisting of flat terrain that is raised sharply above the surrounding area on at least one side. Often one or more sides ha ...
in central Mexico roughly coterminous with present-day
Mexico City
Mexico City ( es, link=no, Ciudad de México, ; abbr.: CDMX; Nahuatl: ''Altepetl Mexico'') is the capital and largest city of Mexico, and the most populous city in North America. One of the world's alpha cities, it is located in the Valley o ...
and the eastern half of the
State of Mexico
The State of Mexico ( es, Estado de México; ), officially just Mexico ( es, México), is one of the 32 federal entities of the United Mexican States. Commonly known as Edomex (from ) to distinguish it from the name of the whole country, it is ...
. Surrounded by mountains and volcanoes, the Valley of Mexico was a centre for several
pre-Columbian
In the history of the Americas, the pre-Columbian era spans from the original settlement of North and South America in the Upper Paleolithic period through European colonization, which began with Christopher Columbus's voyage of 1492. Usually, th ...
civilization
A civilization (or civilisation) is any complex society characterized by the development of a state, social stratification, urbanization, and symbolic systems of communication beyond natural spoken language (namely, a writing system).
Ci ...
s, including
Teotihuacan
Teotihuacan (Spanish language, Spanish: ''Teotihuacán'') (; ) is an ancient Mesoamerican city located in a sub-valley of the Valley of Mexico, which is located in the State of Mexico, northeast of modern-day Mexico City. Teotihuacan is ...
, the
Toltec
The Toltec culture () was a Pre-Columbian era, pre-Columbian Mesoamerican culture that ruled a state centered in Tula (Mesoamerican site), Tula, Hidalgo (state), Hidalgo, Mexico, during the Epiclassic and the early Post-Classic period of Mesoam ...
, and the
Aztec
The Aztecs () were a Mesoamerican culture that flourished in central Mexico in the post-classic period from 1300 to 1521. The Aztec people included different Indigenous peoples of Mexico, ethnic groups of central Mexico, particularly those g ...
. The ancient Aztec term ('Land Between the Waters') and the phrase Basin of Mexico are both used at times to refer to the Valley of Mexico. The Basin of Mexico became a well known site that epitomized the scene of early Classic Mesoamerican cultural development as well.
The Valley of Mexico is located in the
Trans-Mexican Volcanic Belt
The Trans-Mexican Volcanic Belt ( es, Eje Volcánico Transversal), also known as the Transvolcanic Belt and locally as the (''Snowy Mountain Range''), is an active volcanic belt that covers central-southern Mexico. Several of its highest peaks h ...
.
The valley contains most of the
Mexico City Metropolitan Area
Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...
, as well as parts of the
State of Mexico
The State of Mexico ( es, Estado de México; ), officially just Mexico ( es, México), is one of the 32 federal entities of the United Mexican States. Commonly known as Edomex (from ) to distinguish it from the name of the whole country, it is ...
,
Hidalgo
Hidalgo may refer to:
People
* Hidalgo (nobility), members of the Spanish nobility
* Hidalgo (surname)
Places
Mexico
* Hidalgo (state), in central Mexico
* Hidalgo, Coahuila, a town in the north Mexican state of Coahuila
* Hidalgo, Nuevo Le ...
,
Tlaxcala
Tlaxcala (; , ; from nah, Tlaxcallān ), officially the Free and Sovereign State of Tlaxcala ( es, Estado Libre y Soberano de Tlaxcala), is one of the 32 states which comprise the Federal Entities of Mexico. It is divided into 60 municipaliti ...
, and
Puebla
Puebla ( en, colony, settlement), officially Free and Sovereign State of Puebla ( es, Estado Libre y Soberano de Puebla), is one of the 32 states which comprise the Federal Entities of Mexico. It is divided into 217 municipalities and its cap ...
. The Basin of Mexico covers approximately in the NNE-SSW direction with length to width dimensions of approximately to The Valley of Mexico can be subdivided into four basins, but the largest and most-studied is the area that contains
Mexico City
Mexico City ( es, link=no, Ciudad de México, ; abbr.: CDMX; Nahuatl: ''Altepetl Mexico'') is the capital and largest city of Mexico, and the most populous city in North America. One of the world's alpha cities, it is located in the Valley o ...
. This section of the valley in particular is colloquially referred to as the "Valley of Mexico".
The valley has a minimum elevation of
above sea level
Height above mean sea level is a measure of the vertical distance (height, elevation or altitude) of a location in reference to a historic mean sea level taken as a vertical datum. In geodesy, it is formalized as ''orthometric heights''.
The comb ...
and is surrounded by mountains and volcanoes that reach elevations of over .
It is an
enclosed valley with no natural outlet for water to flow to the sea although there is a gap to the north where there is a high
mesa
A mesa is an isolated, flat-topped elevation, ridge or hill, which is bounded from all sides by steep escarpments and stands distinctly above a surrounding plain. Mesas characteristically consist of flat-lying soft sedimentary rocks capped by ...
but no high mountain peaks. Within this vulnerable watershed all the native fishes were extinct by the end of the 20th century. Hydrologically, the valley has three features. The first feature is the lakebeds of five now-extinct lakes, which are located in the southernmost and largest of the four sub-basins. The other two features are
piedmont
it, Piemontese
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, and the mountainsides that collect the precipitation that eventually flows to the lake area. These last two are found in all four of the sub-basins of the valley.
Today, the Valley drains through a series of artificial canals to the
Tula River
The Tula River ( es, Río Tula) is a river in Hidalgo State in central Mexico, and a tributary of the Moctezuma River.
Geography
It runs through the city of Tula de Allende and begins as a drainage channel for the Valley of Mexico, which contain ...
, and eventually the
Pánuco River
The Pánuco River ( es, Río Pánuco, ), also known as the ''Río de Canoas'', is a river in Mexico fed by several tributaries including the Moctezuma River and emptying into the Gulf of Mexico. The river is approximately long and passes throug ...
and the
Gulf of Mexico
The Gulf of Mexico ( es, Golfo de México) is an oceanic basin, ocean basin and a marginal sea of the Atlantic Ocean, largely surrounded by the North American continent. It is bounded on the northeast, north and northwest by the Gulf Coast of ...
.
Seismic activity
An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in intensity, from ...
is frequent here, and the valley is an earthquake-prone zone.
The valley has been inhabited for at least 12,000 years, attracting humans with its mild climate (average temperatures between 12 and 15 °C, or 54 and 59 °F), abundant game and ability to support large-scale agriculture.
Civilizations that have arisen in this area include the
Teotihuacan
Teotihuacan (Spanish language, Spanish: ''Teotihuacán'') (; ) is an ancient Mesoamerican city located in a sub-valley of the Valley of Mexico, which is located in the State of Mexico, northeast of modern-day Mexico City. Teotihuacan is ...
(800 BC to 800 AD) the
Toltec Empire
The Toltec Empire'', ''Toltec Kingdom or Altepetl Tollan was a political entity in modern Mexico. It existed through the classic and post-classic periods of Mesoamerican chronology, but gained most of its power in the post-classic. During this t ...
(10th to 13th century) and the
Aztec Empire
The Aztec Empire or the Triple Alliance ( nci, Ēxcān Tlahtōlōyān, Help:IPA/Nahuatl, jéːʃkaːn̥ t͡ɬaʔtoːˈlóːjaːn̥ was an alliance of three Nahua peoples, Nahua altepetl, city-states: , , and . These three city-states ruled ...
(1325 to 1521).
When the Spaniards arrived in the Valley of Mexico, it had one of the highest population concentrations in the world with about one million people.
After the
Conquest
Conquest is the act of military subjugation of an enemy by force of arms.
Military history provides many examples of conquest: the Roman conquest of Britain, the Mauryan conquest of Afghanistan and of vast areas of the Indian subcontinent, t ...
, the Spaniards rebuilt the largest and most dominant city here,
Tenochtitlan
, ; es, Tenochtitlan also known as Mexico-Tenochtitlan, ; es, México-Tenochtitlan was a large Mexican in what is now the historic center of Mexico City. The exact date of the founding of the city is unclear. The date 13 March 1325 was ...
, renaming it Mexico City. The valley used to contain five lakes called
Lake Zumpango
Lake Zumpango was an endorheic lake formerly located in the Valley of Mexico. It was important area for Mesoamerican cultural development in central Mexico.
The endorheic basin located in the north of State of Mexico, in the borough of municipa ...
, Lake Xaltocan,
Lake Xochimilco
Lake Xochimilco (; nah, Xōchimīlco, ) is an ancient endorheic lake, located in the present-day Borough of Xochimilco in southern Mexico City.
The lake is within the Valley of Mexico hydrological basin, in central Mexico.
History
Geolo ...
,
Lake Chalco
Lake Chalco was an endorheic lake formerly located in the Valley of Mexico, and was important for Mesoamerican cultural development in central Mexico. The lake was named after the ancient city of Chalco on its former eastern shore.
Geography
L ...
and the largest,
Texcoco, covering about of the valley floor,
but as the Spaniards expanded Mexico City, they began to drain the lakes' waters to control flooding.
Although violence and disease significantly lowered the population of the valley after the Conquest, by 1900 it was again over one million people.
The 20th and 21st centuries have seen an explosion of population in the valley along with the growth of industry. Since 1900, the population has doubled every fifteen years. Today, around 21 million people live in the Mexico City Metropolitan Area which extends throughout almost all of the valley into the states of Mexico and Hidalgo.
The growth of a major urban industrial centre in an enclosed basin has created significant air and water quality issues for the valley. Wind patterns and
thermal inversion
In meteorology, an inversion is a deviation from the normal change of an atmospheric property with altitude. It almost always refers to an inversion of the air temperature lapse rate, in which case it is called a temperature inversion. N ...
s trap contaminants in the valley. Over-extraction of ground water has caused new flooding problems for the city as it sinks below the historic lake floor. This causes stress on the valley's drainage system, requiring new tunnels and canals to be built.
History of human habitation
First human habitation
The Valley of Mexico attracted prehistoric humans because the region was rich in biodiversity and had the capacity of growing substantial crops.
Generally speaking, humans in
Mesoamerica
Mesoamerica is a historical region and cultural area in southern North America and most of Central America. It extends from approximately central Mexico through Belize, Guatemala, El Salvador, Honduras, Nicaragua, and northern Costa Rica. W ...
, including central Mexico, began to leave a hunter-gatherer existence in favor of agriculture sometime between the end of the
Pleistocene
The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fina ...
epoch
In chronology and periodization, an epoch or reference epoch is an instant in time chosen as the origin of a particular calendar era. The "epoch" serves as a reference point from which time is measured.
The moment of epoch is usually decided by ...
and the beginning of the
Holocene
The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togethe ...
.
The oldest known human settlement in the Valley of Mexico is located in
Tlapacoya, located on what was the edge of Lake Chalco in the southeast corner of the valley in contemporary Mexico State. There is reliable archeological evidence to suggest that the site dates as far back as 12,000 BC. After 10,000 BC, the number of artifacts found increases significantly. There are also other early sites such as those in Tepexpan, Los Reyes Acozac,
San Bartolo Atepehuacan,
Chimalhuacán
Chimalhuacán () (Nahuatl for "place of those who have shields") is a city and Municipalities of Mexico, municipality located in the eastern part of State of Mexico, Mexico. It lies just outside the northeast border of Mexico City and is part of ...
and
Los Reyes La Paz but they remain undated. Human remains and artifacts such as obsidian blades have been found at the Tlapacoya site that has been dated as far back as 20,000 BC, when the valley was semi-arid and contained species like
camel
A camel (from: la, camelus and grc-gre, κάμηλος (''kamēlos'') from Hebrew or Phoenician: גָמָל ''gāmāl''.) is an even-toed ungulate in the genus ''Camelus'' that bears distinctive fatty deposits known as "humps" on its back. C ...
s,
bison
Bison are large bovines in the genus ''Bison'' (Greek: "wild ox" (bison)) within the tribe Bovini. Two extant and numerous extinct species are recognised.
Of the two surviving species, the American bison, ''B. bison'', found only in North Ame ...
and horses that could be hunted by man. However, the precise dating of these artifacts has been disputed.
![Museo paleontologico de Tocuila-mandibula](https://upload.wikimedia.org/wikipedia/commons/1/1c/Museo_paleontologico_de_Tocuila-mandibula.JPG)
Giant
Columbian mammoth
The Columbian mammoth (''Mammuthus columbi'') is an extinct species of mammoth that inhabited the Americas as far north as the Northern United States and as far south as Costa Rica during the Pleistocene epoch. It was one of the last in a line ...
s once populated the area, and the valley contains the most extensive mammoth kill sites in Mexico. Most of the sites are located on what were the shores of Lake Texcoco in the north of the Federal District and the adjacent municipalities of Mexico State such as in
Santa Isabel Ixtapan Santa Isabel Ixtapan is a community which is part of the municipality of San Salvador Atenco in the State of Mexico, Mexico. It has 4,125 inhabitants and lies 2,240 meters above sea level.
The area is known for having one of the largest and best-s ...
,
Los Reyes Acozac Los Reyes Acozac is a community that belongs to the municipality of Tecámac in the State of Mexico in Mexico
Mexico (Spanish language, Spanish: México), officially the United Mexican States, is a List of sovereign states, country in the so ...
,
Tepexpan
Tepexpan is the largest town in the Acolman municipality in the State of Mexico, Mexico. The population was 48,103 as of the 2005 Mexican census.
One of the most interesting aspects of this town is the discovery of an early Mesoamerican skeleton ...
and
Tlanepantla.
Mammoth bones are still occasionally found in farmland here. They have been discovered in many parts of the Federal District itself, particularly during the construction of the city's
Metro lines and in the neighborhoods of
Del Valle in the center,
Lindavista
Lindavista is a neighbourhood in the north of Mexico City, in the administrative district of Gustavo A. Madero, D.F., Gustavo A. Madero. The streets in Lindavista are named after cities in Latin America.
History
It was founded in 1932 as a re ...
to the center-north and
Coyoacán
Coyoacán ( , ) is a borough (''demarcación territorial'') in Mexico City. The former village is now the borough's "historic center". The name comes from Nahuatl and most likely means "place of coyotes", when the Aztecs named a pre-Hispanic vil ...
in the south of the city. The symbol for Line 4's Talisman station of the Mexico City Metro is a mammoth, due to the fact that so many bones were uncovered during its construction. However, the richest site for mammoth remains in the valley is at the
Paleontological Museum in Tocuila The Paleontological Museum in Tocuila (Museo Paleontológico en Tocuila) is a fossil museum located in Municipality of Texcoco, State of Mexico, central Mexico.
It displays part of one of the richest deposits of Late Pleistocene fauna in America. ...
, a site located near the town of
Texcoco in Mexico State.
Although there is some evidence around the old lakeshores that the first populations here survived by hunting, gathering, and possibly by scavenging, evidence from this time period is scarce.
Pre-Teotihuacan
Tlatilco
Tlatilco was a large pre-Columbian village in the Valley of Mexico situated near the modern-day town of the same name in the Mexican Federal District. It was one of the first chiefdom centers to arise in the Valley, flourishing on the western sho ...
was a large
pre-Columbian
In the history of the Americas, the pre-Columbian era spans from the original settlement of North and South America in the Upper Paleolithic period through European colonization, which began with Christopher Columbus's voyage of 1492. Usually, th ...
village and culture in the Valley of Mexico situated near the modern-day town of the same name in the
Mexican Federal District
Mexico City ( es, link=no, Ciudad de México, ; abbr.: CDMX; Nahuatl: ''Altepetl Mexico'') is the capital and largest city of Mexico, and the most populous city in North America. One of the world's alpha cities, it is located in the Valley of M ...
. It was one of the first significant population centers to arise in the valley, flourishing on the western shore of Lake Texcoco during the
Middle Pre-Classic period, between 1200 BC and 200 BC.
It was originally classified as a
necropolis
A necropolis (plural necropolises, necropoles, necropoleis, necropoli) is a large, designed cemetery with elaborate tomb monuments. The name stems from the Ancient Greek ''nekropolis'', literally meaning "city of the dead".
The term usually im ...
when it was first excavated, but it was determined that the many burials there were under houses of which nothing remains. It was then classified as a major chiefdom center. The Tlatilcans were an agricultural people growing beans,
amaranth
''Amaranthus'' is a cosmopolitan genus of annual or short-lived perennial plants collectively known as amaranths. Some amaranth species are cultivated as leaf vegetables, pseudocereals, and ornamental plants. Catkin-like cymes of densely pack ...
, squash and
chili pepper
Chili peppers (also chile, chile pepper, chilli pepper, or chilli), from Nahuatl '' chīlli'' (), are varieties of the berry-fruit of plants from the genus ''Capsicum'', which are members of the nightshade family Solanaceae, cultivated for ...
s, reaching their peak from 1000 to 700 BC.
The next-oldest confirmed civilization is in the far south of the valley and is called
Cuicuilco
Cuicuilco is an important archaeological site located on the southern shore of Lake Texcoco in the southeastern Valley of Mexico, in what is today the borough of Tlalpan in Mexico City. Some historians believe this settlement goes back to 1400 B ...
.
This archaeological site is located where
Avenida Insurgentes Sur crosses the
Anillo Periférico
The Anillo Periférico (Spanish for ''peripheral ring'') is the outer beltway
A ring road (also known as circular road, beltline, beltway, circumferential (high)way, loop, bypass or orbital) is a road or a series of connected roads encirc ...
in the
Tlalpan
Tlalpan ( nci, Tlālpan, , place on the earth, ) is a borough (''demarcación territorial'') in Mexico City. It is the largest borough, with over eighty percent under conservation as forest and other ecologically sensitive area. The rest, almost ...
borough of the city. The old settlement once extended far beyond the boundaries of the current site, but it is buried under lava from one of the volcanic eruptions that led to its demise, and much of the modern city is built over this lava. The settlement was located where an old river delta used to form in the valley with waters from Mount Zacatépetl located in what is now the Tlalpan Forest. Cuicuilco was believed to have reached city status by 1200 BC and began to decline around 100 BC - AD 150. However, even though the ceremonial pyramid was abandoned, the site remained a location to leave offerings up to AD 400, although lava from the nearby
Xitle
Xitle ( Nahuatl, "navel") is a monogenetic volcano in the Ajusco range in Cumbres del Ajusco National Park. It is located in the Tlalpan borough in the southwestern part of Mexico City. It is an ash cone volcano with a conical form, round base, a ...
volcano completely covered it.
Teotihuacan and the Toltecs
Around 2,000 years ago, the Valley of Mexico became one of the world's most densely populated areas and has remained so since.
After the decline of Cuicuilco, the population concentration shifted north, to the city of Teotihuacan and later to
Tula
Tula may refer to:
Geography
Antarctica
*Tula Mountains
*Tula Point
India
*Tulā, a solar month in the traditional Indian calendar
Iran
* Tula, Iran, a village in Hormozgan Province
Italy
* Tula, Sardinia, municipality (''comune'') in the pr ...
, both outside the lake's region of the valley.
Teotihuacan became an organized village around 800 BC but it was around 200 BC that it began to reach its height. When it did, the city had approximately 125,000 inhabitants and covered of territory. It was dedicated primarily to the
obsidian
Obsidian () is a naturally occurring volcanic glass formed when lava extrusive rock, extruded from a volcano cools rapidly with minimal crystal growth. It is an igneous rock.
Obsidian is produced from felsic lava, rich in the lighter elements s ...
trade and at its peak was an important religious center and
pilgrimage
A pilgrimage is a journey, often into an unknown or foreign place, where a person goes in search of new or expanded meaning about their self, others, nature, or a higher good, through the experience. It can lead to a personal transformation, aft ...
for the valley.
In the early 8th century, with the rise of the
Toltec
The Toltec culture () was a Pre-Columbian era, pre-Columbian Mesoamerican culture that ruled a state centered in Tula (Mesoamerican site), Tula, Hidalgo (state), Hidalgo, Mexico, during the Epiclassic and the early Post-Classic period of Mesoam ...
empire, Teotihuacan ceased to be a major urban centre and the population shifted to Tollan or Tula on the northern front of the Valley of Mexico.
Aztec Empire
After the end of the Toltec empire in the 13th century and the decline of the city of Tula, the population shifted once again, this time to the lakes region of the valley. With this migration came the concept of a city-state based on the Toltec model. By the end of the 13th century, some fifty small urban units, semi-autonomous and with their own religious centers, had sprung up around the lakeshores of the valley. These remained intact with a population of about 10,000 each under Aztec rule and survived into the colonial period. All of these city-states, including the largest and most powerful,
Tenochtitlan
, ; es, Tenochtitlan also known as Mexico-Tenochtitlan, ; es, México-Tenochtitlan was a large Mexican in what is now the historic center of Mexico City. The exact date of the founding of the city is unclear. The date 13 March 1325 was ...
, with more than 150,000 inhabitants, claimed descent from the Toltecs. None of these cities was completely autonomous or self-sufficient, resulting in a conflictive political situation, and a complex system of agriculture in the valley.
These city-states had similar governmental structures based on the need to control flooding and store water for irrigating crops. Many of the institutions created by these hydraulic societies, such as the building and maintenance of chinampas, aqueducts and dikes, were later co-opted by the Spanish during the colonial period.
The largest and most dominant city at the time of the Spanish conquest was
Tenochtitlan
, ; es, Tenochtitlan also known as Mexico-Tenochtitlan, ; es, México-Tenochtitlan was a large Mexican in what is now the historic center of Mexico City. The exact date of the founding of the city is unclear. The date 13 March 1325 was ...
. It was founded by the
Mexica
The Mexica (Nahuatl: , ;''Nahuatl Dictionary.'' (1990). Wired Humanities Project. University of Oregon. Retrieved August 29, 2012, frolink/ref> singular ) were a Nahuatl-speaking indigenous people of the Valley of Mexico who were the rulers of ...
(
Aztecs
The Aztecs () were a Mesoamerican culture that flourished in central Mexico in the post-classic period from 1300 to 1521. The Aztec people included different Indigenous peoples of Mexico, ethnic groups of central Mexico, particularly those g ...
) on a small island in the western part of Lake Texcoco in 1325, and was extended with the use of
chinampa
Chinampa ( nah, chināmitl ) is a technique used in Mesoamerican agriculture which relies on small, rectangular areas of fertile arable land to grow crops on the shallow lake beds in the Valley of Mexico. They are built up on wetlands of a lake o ...
s, human-made extensions of agricultural land into the southern lake system, to increase productive agricultural land, covering about .
The inhabitants controlled the lake with a sophisticated system of
dike
Dyke (UK) or dike (US) may refer to:
General uses
* Dyke (slang), a slang word meaning "lesbian"
* Dike (geology), a subvertical sheet-like intrusion of magma or sediment
* Dike (mythology), ''Dikē'', the Greek goddess of moral justice
* Dikes ...
s, canals and
sluice
Sluice ( ) is a word for a channel controlled at its head by a movable gate which is called a sluice gate. A sluice gate is traditionally a wood or metal barrier sliding in grooves that are set in the sides of the waterway and can be considered ...
s. Much of the surrounding land in the valley was
terraced and farmed as well, with a network of
aqueducts channeling fresh water from springs in the mountainsides into the city itself.
Despite being the dominant power, the need to rely on resources from other parts of the valley led to the
Aztec Triple Alliance
The Aztec Empire or the Triple Alliance ( nci, Ēxcān Tlahtōlōyān, jéːʃkaːn̥ t͡ɬaʔtoːˈlóːjaːn̥ was an alliance of three Nahua city-states: , , and . These three city-states ruled that area in and around the Valley of Mexico ...
between Tenochtitlan,
Texcoco and
Tlacopan
Tlacopan, also called Tacuba, was a Tepanec / Mexica altepetl on the western shore of Lake Texcoco. The site is today the neighborhood of Tacuba, in Mexico City.
Etymology
The name comes from Classical Nahuatl ''tlacōtl'', "stem" or "rod" and ...
at the beginning of the empire. However, by the time the Spanish arrived in 1519, Tenochtitlan had become the dominant power of the three, causing grievances that the Spaniards were able to exploit.
However, despite Tenochtitlan's power outside the valley, it never completely controlled all of the valley itself, with the
altepetl
The (, plural ''altepeme'' or ''altepemeh'') was the local, ethnically-based political entity, usually translated into English as "city-state," of pre-Columbian Nahuatl-speaking societiesSmith 1997 p. 37 in the Americas. The ''altepetl'' was co ...
of Tlaxcala the most prominent example.
By 1520, the estimated population of the valley was over 1,000,000 people.
Spanish colonial rule and the Mexico City metropolitan area
After the
Spanish conquest of the Aztec empire
The Spanish conquest of the Aztec Empire, also known as the Conquest of Mexico or the Spanish-Aztec War (1519–21), was one of the primary events in the Spanish colonization of the Americas. There are multiple 16th-century narratives of the eve ...
in 1521, the Spanish rebuilt and renamed Tenochtitlan as Mexico City. They started with essentially the same size and layout as the Aztec city but as the centuries progressed, the city grew as the lakes shrank. Just after the conquest, disease and violence had decreased the population in the valley, especially of the native peoples, but after that, the population grew all through the colonial period and in the century after
independence
Independence is a condition of a person, nation, country, or state in which residents and population, or some portion thereof, exercise self-government, and usually sovereignty, over its territory. The opposite of independence is the statu ...
.
By the early 20th century, the population of Mexico City alone had risen to over one million people. A population explosion began early in the 20th century, with the population of the city itself doubling approximately every 15 years since 1900, partly attributed to the fact that the federal government has favored development of the metropolitan area over other areas of the country.
This has spurred investment in
infrastructure
Infrastructure is the set of facilities and systems that serve a country, city, or other area, and encompasses the services and facilities necessary for its economy, households and firms to function. Infrastructure is composed of public and priv ...
for the city, such as
electricity
Electricity is the set of physical phenomena associated with the presence and motion of matter that has a property of electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as described ...
, other power sources,
water supply
Water supply is the provision of water by public utilities, commercial organisations, community endeavors or by individuals, usually via a system of pumps and pipes. Public water supply systems are crucial to properly functioning societies. Thes ...
and
drainage
Drainage is the natural or artificial removal of a surface's water and sub-surface water from an area with excess of water. The internal drainage of most agricultural soils is good enough to prevent severe waterlogging (anaerobic conditio ...
. These have attracted businesses which in turn have attracted more population. Since the 1950s, urbanization has spread out from beyond the bounds of the Federal District to the surrounding jurisdictions, especially to the north into the State of Mexico making for the Mexico City Metropolitan area, which fills most of the valley.
Today, this metropolitan area accounts for 45 per cent of the country's industrial activity, 38 percent of GNP, and 25 percent of the population.
Much of its industry is concentrated in the northern part of the Federal District and the adjoining cities in the state of Mexico.
While population growth has slowed and even declined in the city proper, the outer limits of the metropolitan area keep growing. Much of this growth has occurred on the mountainsides of the valley, in the form of illegal settlements in ecologically sensitive areas.
Overall urban settlement in the valley has expanded from about in 1940 to in 1990.
The metropolitan area has about 21 million residents and about 6 million cars.
Air pollution
Mexico City is
vulnerable to severe air pollution problems due to its altitude, its being surrounded by mountains and the winds patterns of the area.
The altitude, with its low oxygen levels, makes for poor combustion of
fossil fuel
A fossil fuel is a hydrocarbon-containing material formed naturally in the Earth's crust from the remains of dead plants and animals that is extracted and burned as a fuel. The main fossil fuels are coal, oil, and natural gas. Fossil fuels m ...
s leading to unsafe levels of
nitrogen oxide Nitrogen oxide may refer to a binary compound of oxygen and nitrogen, or a mixture of such compounds:
Charge-neutral
*Nitric oxide (NO), nitrogen(II) oxide, or nitrogen monoxide
*Nitrogen dioxide (), nitrogen(IV) oxide
* Nitrogen trioxide (), or n ...
s,
hydrocarbons
In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic, and their odors are usually weak or ex ...
, and
carbon monoxide
Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...
.
The valley is surrounded by mountain ranges with one small opening to the north. The surrounding mountains and climate patterns here make it difficult to clear out the smog produced.
The valley has internal wind patterns which circulate around the valley without a prevailing wind to push contaminants in a single direction.
The most significant climatic phenomena here is "thermal inversion," which is prevalent in the winter months when the cooler air of the valley is trapped by relatively warmer air above. Adding to this is that prevailing winds outside the valley move from north to south, in through the Valley's one opening, where incidentally most of the region's industry is located.
These factors diminish in the summer and the situation is helped by the arrival of the rainy season,
but the valley's southern latitude and the abundance of sunlight allows for dangerous levels of
ozone
Ozone (), or trioxygen, is an inorganic molecule with the chemical formula . It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope , breaking down in the lo ...
and other dangerous compounds.
![Smog boven mexico city november 1985](https://upload.wikimedia.org/wikipedia/commons/5/5d/Smog_boven_mexico_city_november_1985.jpg)
While still considered one of the most polluted places on the planet, the valley's air pollution problems are not as bad as they were several decades ago.
One major problem that was brought under control was the
lead
Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...
contamination in the air with the introduction of
unleaded gasoline
Gasoline (; ) or petrol (; ) (see ) is a transparent, petroleum-derived flammable liquid that is used primarily as a fuel in most Spark-ignition engine, spark-ignited internal combustion engines (also known as petrol engines). It consists ...
. Two other contaminants that have been brought under control are carbon monoxide and
sulfur dioxide
Sulfur dioxide (IUPAC-recommended spelling) or sulphur dioxide (traditional Commonwealth English) is the chemical compound with the formula . It is a toxic gas responsible for the odor of burnt matches. It is released naturally by volcanic activ ...
.
The contamination problems that remain are primarily with ozone and
fine particles
Particulates – also known as atmospheric aerosol particles, atmospheric particulate matter, particulate matter (PM) or suspended particulate matter (SPM) – are microscopic particles of solid or liquid matter suspended in the air. The ter ...
(
soot
Soot ( ) is a mass of impure carbon particles resulting from the incomplete combustion of hydrocarbons. It is more properly restricted to the product of the gas-phase combustion process but is commonly extended to include the residual pyrolysed ...
) (between 2.5
micrometers
The micrometre (American and British English spelling differences#-re, -er, international spelling as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American and British English spelling differences# ...
and 10 micrometers).
Thirty to fifty percent of the time, Mexico City's levels of
fine particles
Particulates – also known as atmospheric aerosol particles, atmospheric particulate matter, particulate matter (PM) or suspended particulate matter (SPM) – are microscopic particles of solid or liquid matter suspended in the air. The ter ...
of ten micrometers, the most dangerous, exceed levels recommended by the
World Health Organization
The World Health Organization (WHO) is a specialized agency of the United Nations responsible for international public health. The WHO Constitution states its main objective as "the attainment by all peoples of the highest possible level of h ...
.
In the 1940s, before large-scale burning of fossil fuels in the area, the visibility of the valley was about , allowing for daily viewing of the mountain ranges that surround the valley, including the snow-capped volcanoes of Popocatepetl and Iztaccihuatl. Since that time, the average visibility has come down to about . Mountain peaks are now rarely visible from the city itself.
While reduced visibility in the valley was due to sulfur emissions in the past, it is now due to
fine particles
Particulates – also known as atmospheric aerosol particles, atmospheric particulate matter, particulate matter (PM) or suspended particulate matter (SPM) – are microscopic particles of solid or liquid matter suspended in the air. The ter ...
in the air.
The effects on humans living in an enclosed, contaminated environment have been documented, especially by
Nobel Prize
The Nobel Prizes ( ; sv, Nobelpriset ; no, Nobelprisen ) are five separate prizes that, according to Alfred Nobel's will of 1895, are awarded to "those who, during the preceding year, have conferred the greatest benefit to humankind." Alfr ...
winner Dr
Mario J. Molina
Mario José Molina-Pasquel Henríquez (19 March 19437 October 2020), known as Mario Molina, was a Mexican chemist. He played a pivotal role in the discovery of the Antarctic ozone hole, and was a co-recipient of the 1995 Nobel Prize in Chemis ...
. He claims
fine particle
Particulates – also known as atmospheric aerosol particles, atmospheric particulate matter, particulate matter (PM) or suspended particulate matter (SPM) – are microscopic particles of solid or liquid matter suspension (chemistry), suspen ...
pollution is the greatest concern because of lung damage.
According to him, the city's residents lose about 2.5 million working days every year due to health problems associated with
fine particles
Particulates – also known as atmospheric aerosol particles, atmospheric particulate matter, particulate matter (PM) or suspended particulate matter (SPM) – are microscopic particles of solid or liquid matter suspended in the air. The ter ...
.
Hydrology
The Valley of Mexico is a closed or
endorheic basin
An endorheic basin (; also spelled endoreic basin or endorreic basin) is a drainage basin that normally retains water and allows no outflow to other external bodies of water, such as rivers or oceans, but drainage converges instead into lakes ...
which geologically divides into three hydrologic zones, the low plain, which is essentially the bed of now-extinct lakes, the piedmont area and the surrounding mountains. The old lakebeds correspond to the lowest elevations of the valley in the south are mostly clay with a high water content and are almost entirely covered by urban development.
In the piedmont area, these clays become mixed with silts and sands, and in some areas close to the mountains, the piedmont is largely composed of
basalt
Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial ...
from old lava flows. The valley is enclosed completely by mountain ranges, from which flow rain and melting snow into the valley's hydraulic system. This groundwater flow produces a number of
springs in the foothills and
upwelling
Upwelling is an oceanographic phenomenon that involves wind-driven motion of dense, cooler, and usually nutrient-rich water from deep water towards the ocean surface. It replaces the warmer and usually nutrient-depleted surface water. The nutr ...
s in the valley floor.
This underground flow is the source of the five aquifers that provide much of the drinking water to Mexico City located in Soltepec,
Apan
Apan is a city and one of the 84 municipalities of Hidalgo, in central-eastern Mexico. The municipality covers an area of 346.9 km².
Overview
As of 2005, the municipality had a total population of 39,247.
It was an important site in the Wa ...
,
Texcoco,
Chalco-
Amecameca
Amecameca is a municipality located in the eastern panhandle of Mexico State between Mexico City and the Iztaccíhuatl and Popocatépetl volcanos of the Sierra Nevada mountain range. It is located on federal highway 115 which leads to Cuautla, w ...
and underneath Mexico City itself.
Old lake system
![Lake Chalco 1847](https://upload.wikimedia.org/wikipedia/commons/2/29/Lake_Chalco_1847.PNG)
Before the 20th century, the Mexico City portion of the valley contained a series of lakes, with saline lakes to the north near the town of Texcoco and freshwater ones to the south.
The five lakes, Zumpango, Xaltoca, Xochimilco, Chalco, and the largest, Texcoco used to cover about of the basin floor.
Small mountains such as the
Sierra de Guadalupe and Mount Chiconaultla partially separated the lakes from each other.
All the other lakes flowed toward the lower Lake Texcoco, which was saline due to evaporation.
The lakes were fed by a number of rivers such as the San Joaquin, San Antonio Abad, Tacubaya, Becerra, Mixcoac and Magdalena Contreras, carrying runoff and snowmelt from the mountains.
Long before the arrival of the Spanish, the lake system had been shrinking due to climate change.
Warmer temperatures had increased evaporation and reduced rainfall in the area so that the lakes’ waters were shallow at about deep as early as the Tlapacoya culture, around 10,000 BC.
During the Aztec Empire, the northern lakes were inaccessible by canoe during the dry season from October to May.
History of water control in the valley
For 2000 years, humans have been interfering with and altering the hydraulic conditions of the valley, especially in the lakes region.
The Aztecs built
dikes
Dyke (UK) or dike (US) may refer to:
General uses
* Dyke (slang), a slang word meaning "lesbian"
* Dike (geology), a subvertical sheet-like intrusion of magma or sediment
* Dike (mythology), ''Dikē'', the Greek goddess of moral justice
* Dikes, ...
for flood control and to separate the
saline water
Saline water (more commonly known as salt water) is water that contains a high concentration of dissolved salts (mainly sodium chloride). On the United States Geological Survey (USGS) salinity scale, saline water is saltier than brackish water, ...
of the northern lakes from the
fresh water
Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does include ...
of the southern ones. After the destruction of Tenochtitlan in 1521, the Spaniards rebuilt the Aztec dikes but found they did not offer enough flood protection.
The arrival of the Spanish and subsequent efforts to drain the area for flood control was a major infrastructure project, called the , was pursued the entire colonial period.
The idea of opening drainage canals first came about after a flood of the colonial city in 1555. The first canal was begun in 1605 to drain the waters of Lake Zumpango north through
Huehuetoca
Huehuetoca is a ''municipio'' (municipality) in State of Mexico, central Mexico, and also the name of its largest town and municipal seat.
Name origins
The name "Huehuetoca" is derived from the Nahuatl ''huehuetocan'', which has several interp ...
which would also divert waters from the
Cuautitlán
Cuautitlán (), is a municipality in the State of Mexico, just north of the northern tip of the Federal District (Distrito Federal) within the Greater Mexico City urban area. The city of Cuautitlán is the municipal seat and makes up most of the ...
River away from the lakes and toward the
Tula River
The Tula River ( es, Río Tula) is a river in Hidalgo State in central Mexico, and a tributary of the Moctezuma River.
Geography
It runs through the city of Tula de Allende and begins as a drainage channel for the Valley of Mexico, which contain ...
. This project was undertaken by
Enrico Martínez
Enrico Martínez, Henri Martín or Heinrich Martin, (Born in Hamburg, date unknown; d. in Mexico in 1632) was cosmographer to the King of Spain, interpreter for the Spanish Inquisition, publisher, and hydraulic engineer.
According to some he was ...
and he devoted 25 years of his life to it. He did succeed in building a canal in this area, calling it Nochistongo, leading waters to the Tula Valley, but the drainage was not sufficient to avoid the Great Flood of 1629 in the city. Another canal, which would be dubbed the "Grand Canal" was built parallel to the Nochistongo one ending in
Tequixquiac
Tequixquiac is a municipality located in the Zumpango Region of the State of Mexico in Mexico. The municipality is located north of Mexico City within the valley that connects the Valley of Mexico with the Mezquital Valley. The name comes from Na ...
. The Grand Canal consists of one main canal, which measures in diameter and long.
The drainage project was continued after independence, with three secondary canals, built between 1856 and 1867. During the presidency of
Porfirio Díaz
José de la Cruz Porfirio Díaz Mori ( or ; ; 15 September 1830 – 2 July 1915), known as Porfirio Díaz, was a Mexican general and politician who served seven terms as President of Mexico, a total of 31 years, from 28 November 1876 to 6 Decem ...
(r. 1876–1911) drainage again became a priority. Díaz completed it officially in 1894, although work continued thereafter.
Despite the Grand Canal's drainage capacity, it did not solve the problem of flooding in the city.
From the beginning of the 20th century, Mexico City began to sink rapidly and pumps needed to be installed in the Grand Canal, which before had drained the valley purely with gravity.
Along with the pumps, the Grand Canal was expanded with a new tunnel through the low mountains called the Xalpa to take the canal past
Tequisquiac.
Even so, the city still suffered floods in 1950 and 1951.
Despite its age, the Grand Canal can still carry out of the valley, but this is significantly less than what it could carry as late as 1975 because continued sinking of the city (as much as ) weakens the system of water collectors and pumps.
As a result, another tunnel, called the
Emisor Central, was built to carry wastewater. Although it is considered the most important pipe in the country, it has been damaged by overuse and corrosion of its diameter walls.
Because of lack of maintenance and gradual decrease in this tunnel's ability to carry water, there is concern that this tunnel will soon fail. It is continuously filled with water, making it impossible to inspect it for problems. If it fails, it would most likely be during the rainy season when it carries the most water, which would cause extensive flooding in the historic center, the airport and the boroughs on the east side.
Because of this, another new drainage project is planned that will cost US$1.3 billion. The project includes new pumping stations, a new drainage tunnel and repairs to the current system of pipes and tunnels to clear blockages and patch leaks.
Over-pumping of groundwater in the 20th century has hastened the disappearance of the lakes. The old lake beds are almost all paved
except for some canals preserved in Xochimilco, mostly for the benefit of visitors who tour them on brightly painted , boats similar to
gondola
The gondola (, ; vec, góndoła ) is a traditional, flat-bottomed Venetian rowing boat, well suited to the conditions of the Venetian lagoon. It is typically propelled by a gondolier, who uses a rowing oar, which is not fastened to the hull ...
s.
Desiccation has had a major environmental impact on the Valley of Mexico.
Drinking water and sinking lands
![Angel am ex](https://upload.wikimedia.org/wikipedia/commons/d/d9/Angel_am_ex.jpg)
Historically, Mexico City's potable water supply came via aqueduct from the mountain springs on the valley sides like that in Chapultepec as most of the water in Lake Texcoco was saline.
These were originally built by the Aztecs and were rebuilt by the Spaniards. In the mid-1850s, potable groundwater was found underneath the city itself, which motivated the large-scale drilling of wells. Today, 70% of Mexico City's water still comes from five principal aquifers in the valley. These aquifers are fed by water from natural springs and runoff from precipitation.
It was only when the population reached about six million that Mexico City started to need to appropriate water from outside the valley.
Today, Mexico City faces a serious water deficit. Because of increased demand from a growing population, increasing industry, and ecosystem degradation in the form of deforestation of the surrounding mountains, more water is leaving the system than is entering. It is estimated that of water is needed to support the potable and agricultural irrigation needs of Mexico City's population.
The main aquifer is being pumped at a rate of , but is only being replaced at , or about half of the extraction rate, leaving a shortfall of .
This over-extraction of groundwater from the old clay lake bed has been causing the land upon which the city rests to collapse and sink. This problem began in the early 20th century as a consequence of the drainage of the valley for flood control. Since the beginning of the 20th century, some areas of Mexico City have sunk .
In 1900, the bottom of the lake was lower than the median level of the city center. By 1974, the lake bottom was higher than the city.
The first signs of dropping ground water levels was the drying up of natural springs in the 1930s, which coincides with the beginning of intensive exploitation of the aquifer system through wells between deep.
Today, Mexico City is sinking between five and forty centimeters (0.2 and 1.3 ft) per year, and its effects are visible.
El Ángel de la Independencia
The Angel of Independence, most commonly known by the shortened name ''El Ángel'' and officially known as ''Monumento a la Independencia'' ("Monument to Independence"), is a victory column on a roundabout on the major thoroughfare of Paseo de ...
("The Angel of Independence") statue, located on
Paseo de la Reforma
Paseo de la Reforma (translated as "Promenade of the Reform") is a wide avenue that runs diagonally across the heart of Mexico City. It was designed at the behest of Emperor Maximilian by Ferdinand von Rosenzweig during the era of the Secon ...
was built in 1910, anchored by a foundation deep beneath what was the surface of the street at that time. However, because the street has sunk around it, steps have been added to allow access to the statue's base.
Subsidence of the valley floor beneath has caused flooding problems as now much of the city has sunk below the natural lake floor. Currently, pumps need to work 24 hours a day all year round to keep control of runoff and wastewater.
Despite this, flooding is still common, especially in the summer rainy season, in lower-lying neighborhoods such as
Iztapalapa
Iztapalapa () is a borough (''demarcación territorial'') in Mexico City, located on the east side of the entity. The borough is named after and centered on the formerly independent municipality of Iztapalapa, which is officially called Iztapalapa ...
, forcing residents to build miniature dikes in front of their houses to prevent heavily polluted rainwater from entering their homes.
Subsidence also causes damage to water and sewer lines, leaving the water distribution system vulnerable to contamination which carries risks to public health.
Measures other than drainage have been implemented to contain flooding in the city. In 1950, dikes were built to confine storm runoff.
Rivers that run through the city were encapsulated in 1950 and 1951.
Rivers such as the Consulado River, Churubusco River and the Remedio River are encased in concrete tunnels which take their waters directly to the drainage system to leave the Valley. Two other rivers, the San Javier and the Tlalnepantla, which used to feed the old lake system, are diverted before they reach the city and their waters now flow directly into the Grand Canal.
No water from these rivers is allowed to sink into the ground to recharge the aquifer. While the rivers and streams that flow down from the mountain peaks still begin the way they always have, their passage through the shantytowns lacking city sanitation schemes that surround Mexico City turns them into open
combined sewer
A combined sewer is a type of gravity sewer with a system of pipes, tunnels, pump stations etc. to transport sewage and urban runoff together to a sewage treatment plant or disposal site. This means that during rain events, the sewage gets dilute ...
s. Therefore, their final stages are frequently culverted or added to the existing major culverted rivers to keep this water from contaminating the aquifer.
See also
*
Mexican Plateau
The Central Mexican Plateau, also known as the Mexican Altiplano ( es, Altiplanicie Mexicana), is a large arid-to-semiarid plateau that occupies much of northern and central Mexico. Averaging above sea level, it extends from the US-Mexico border ...
*
Trans-Mexican Volcanic Belt
The Trans-Mexican Volcanic Belt ( es, Eje Volcánico Transversal), also known as the Transvolcanic Belt and locally as the (''Snowy Mountain Range''), is an active volcanic belt that covers central-southern Mexico. Several of its highest peaks h ...
*
Valleys of Mexico
References
{{DEFAULTSORT:Valley Of Mexico
Mexico
Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...
Mexican Plateau
Trans-Mexican Volcanic Belt
Regions of Mexico
Landforms of Mexico City
Landforms of the State of Mexico
Landforms of Puebla
Landforms of Tlaxcala
Geography of Mesoamerica
Geography of Hidalgo (state)
Geography of Mexico City
Geography of Puebla
Geography of the State of Mexico
Geography of Tlaxcala