Sierra Madre Occidental
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The Sierra Madre Occidental is a major
mountain range A mountain range or hill range is a series of mountains or hills arranged in a line and connected by high ground. A mountain system or mountain belt is a group of mountain ranges with similarity in form, structure, and alignment that have arise ...
system of the North American Cordillera, that runs northwest–southeast through northwestern and western Mexico, and along the
Gulf of California The Gulf of California ( es, Golfo de California), also known as the Sea of Cortés (''Mar de Cortés'') or Sea of Cortez, or less commonly as the Vermilion Sea (''Mar Bermejo''), is a marginal sea of the Pacific Ocean that separates the Baja Ca ...
. The Sierra Madre is part of the
American Cordillera The American Cordillera is a chain of mountain ranges (cordilleras) that consists of an almost continuous sequence of mountain ranges that form the western "backbone" of North America, Central America and South America, with Aconcagua as the h ...
, a chain of mountain ranges (cordillera) that consists of an almost continuous sequence of mountain ranges that form the western 'sounds' of
North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...
,
Central America Central America ( es, América Central or ) is a subregion of the Americas. Its boundaries are defined as bordering the United States to the north, Colombia to the south, the Caribbean Sea to the east, and the Pacific Ocean to the west. ...
,
South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the southe ...
and West Antarctica.


Etymology

The
Spanish Spanish might refer to: * Items from or related to Spain: **Spaniards are a nation and ethnic group indigenous to Spain **Spanish language, spoken in Spain and many Latin American countries **Spanish cuisine Other places * Spanish, Ontario, Can ...
name ''sierra madre'' means "mother mountain range" in English, and ''occidental'' means "western", these thus being the "Western mother mountain range". To the east, from the Spanish ''oriental'' meaning "eastern" in English, the
Sierra Madre Oriental The Sierra Madre Oriental () is a mountain range in northeastern Mexico. The Sierra Madre Oriental is part of the American Cordillera, a chain of mountain ranges (cordillera) that consists of an almost continuous sequence of mountain ranges that f ...
range or "Eastern Mother Mountains" runs generally parallel to the Sierra Madre Occidental along eastern Mexico 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 ...
. The range extends from northern
Sonora Sonora (), officially Estado Libre y Soberano de Sonora ( en, Free and Sovereign State of Sonora), is one of the 31 states which, along with Mexico City, comprise the Administrative divisions of Mexico, Federal Entities of Mexico. The state is d ...
, a state near the Mexico–U.S. border at
Arizona Arizona ( ; nv, Hoozdo Hahoodzo ; ood, Alĭ ṣonak ) is a state in the Southwestern United States. It is the 6th largest and the 14th most populous of the 50 states. Its capital and largest city is Phoenix. Arizona is part of the Fou ...
, southeastwards to 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 ...
and Sierra Madre del Sur ranges. The high
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 ...
that is formed by the range is cut by deep river valleys. This plateau is formed from volcanic rock overlying a basement of metamorphic rock. This uplift has caused changes in weather patterns; increased rainfall occurring in the mountains has provided areas where ecosystems can form in wetter areas than surrounding land. This water source forms watersheds that provide the arid surroundings with water that makes it possible to irrigate and farm crops. The wet ecosystems are islands of biodiversity, differing significantly from what would otherwise be a desert landscape. Oak forests are the predominant plant life, and extend into the lowland deserts. This forest and canyon land provided a place for a variety of
indigenous people Indigenous peoples are culturally distinct ethnic groups whose members are directly descended from the earliest known inhabitants of a particular geographic region and, to some extent, maintain the language and culture of those original people ...
to live, until Spanish settlers with associated
mestizo (; ; fem. ) is a term used for racial classification to refer to a person of mixed Ethnic groups in Europe, European and Indigenous peoples of the Americas, Indigenous American ancestry. In certain regions such as Latin America, it may also r ...
s came into the area to found towns for the
silver mines Silver mining is the extraction of silver from minerals, starting with mining. Because silver is often found in intimate combination with other metals, its extraction requires elaborate technologies. In 2008, ca.25,900 metric tons were consumed ...
in the area. The major industries in the area now are
agriculture Agriculture or farming is the practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that enabled people to ...
and forestry, which have become contentious because of
land degradation Land degradation is a process in which the value of the biophysical environment is affected by a combination of human-induced processes acting upon the land. It is viewed as any change or disturbance to the land perceived to be deleterious ...
and the native population's opposition to these practices.


Geography

The range trends from the north to southeast. Canyons cut by the rivers of the wet western slopes exist in addition to those of the northeast slopes, notably the
Copper Canyon Copper Canyon (Spanish: Barrancas del Cobre) is a group of six distinct canyons in the Sierra Madre Occidental in the southwestern part of the state of Chihuahua in northwestern Mexico that is in size. The canyons were formed by six rivers tha ...
.


Location

The range runs parallel to the Pacific coast of Mexico, from just south of the Arizona-Sonora border southeast through eastern
Sonora Sonora (), officially Estado Libre y Soberano de Sonora ( en, Free and Sovereign State of Sonora), is one of the 31 states which, along with Mexico City, comprise the Administrative divisions of Mexico, Federal Entities of Mexico. The state is d ...
, western Chihuahua, Sinaloa, Durango,
Zacatecas , image_map = Zacatecas in Mexico (location map scheme).svg , map_caption = State of Zacatecas within Mexico , coordinates = , coor_pinpoint = , coordinates_footnotes = , subdivision_type ...
,
Nayarit Nayarit (), officially the Free and Sovereign State of Nayarit ( es, Estado Libre y Soberano de Nayarit), is one of the 31 states that, along with Mexico City, comprise the Federal Entities of Mexico. It is divided in 20 municipalities and its ...
, Jalisco, Aguascalientes to
Guanajuato Guanajuato (), officially the Free and Sovereign State of Guanajuato ( es, Estado Libre y Soberano de Guanajuato), is one of the 32 states that make up the Federal Entities of Mexico. It is divided into 46 municipalities and its capital city i ...
, where it joins with the Sierra Madre del Sur and the Eje Volcánico Transversal (Transverse Volcanic Axis) of central Mexico after crossing . The mountains range from from the
Gulf of California The Gulf of California ( es, Golfo de California), also known as the Sea of Cortés (''Mar de Cortés'') or Sea of Cortez, or less commonly as the Vermilion Sea (''Mar Bermejo''), is a marginal sea of the Pacific Ocean that separates the Baja Ca ...
in the north, but begin to approach within of the
Pacific The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...
in the south. These mountains are generally considered to be part of the much larger
American cordillera The American Cordillera is a chain of mountain ranges (cordilleras) that consists of an almost continuous sequence of mountain ranges that form the western "backbone" of North America, Central America and South America, with Aconcagua as the h ...
, the mountains extending from
Alaska Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U.S., ...
down to these across western North America.


Regions

''Sierra Tarahumara'' or ''Tarahumara'' is the name for the region of the Sierra Madre beginning at the Durango border and extending north. This name comes from the Tarahumara natives. This is a dramatic landscape of steep mountains formed by a high plateau that has been cut through with canyons including
Copper Canyon Copper Canyon (Spanish: Barrancas del Cobre) is a group of six distinct canyons in the Sierra Madre Occidental in the southwestern part of the state of Chihuahua in northwestern Mexico that is in size. The canyons were formed by six rivers tha ...
, larger and, in places, deeper than the
Grand Canyon The Grand Canyon (, yuf-x-yav, Wi:kaʼi:la, , Southern Paiute language: Paxa’uipi, ) is a steep-sided canyon carved by the Colorado River in Arizona, United States. The Grand Canyon is long, up to wide and attains a depth of over a m ...
. This plateau has an average elevation of with most of the more eroded canyons on the western slope, due to the higher moisture content. The highest elevations occur in the Tarahumara range. The exact elevations of the highest peaks are not known within accurate enough ranges to determine their relative elevation. The highest point is probably
Cerro Mohinora Cerro Mohinora is an extinct volcano that is part of the Sierra Madre Occidental mountain range in the Mexican state of Chihuahua (state), Chihuahua located in the municipality of Guadalupe y Calvo. Cerro Mohinora is the highest point in the stat ...
, located at . Estimates for the height of the mountain start around and go up to . However, Cerro Barajas, at , may be as high as although other sources give as the elevation. Cerro Gordo, at , may have an elevation between and . The southern end of the mountains may be referred to as the Sierra Huichola. In this area, the Sierra Madre begins to give way to the basin and range province. Subranges of this area include the Sierra de Alica and the Sierra Pajaritos, both in Nayarit, and the
Sierra los Huicholes The Sierra los Huicholes is a mountain range in western Mexico. It is located in the states of Nayarit, Jalisco, and Zacatecas. The Sierra los Huicholes is part of the Sierra Madre Occidental, and is located in the southern portion of the range. ...
,
Sierra de Morones The Sierra de Morones is a mountain range in west-central Mexico. Geography The Sierra de Morones extends north and south through the state of Zacatecas. The Sierra, together with the Sierra Fría to the east and the Sierra los Huicholes to th ...
, Sierra Nochistlan, and
Sierra Fría The Sierra Fría is a mountain range in central Mexico. It forms the northwestern border of Aguascalientes state and extends into adjacent Zacatecas, west of the city of Aguascalientes City, Aguascalientes. Geography The Sierra Fría is the sout ...
extending eastwards into Jalisco, Zacatecas, and Aguascalientes.


Water

The mountains act as a source of water, in an otherwise
arid A region is arid when it severely lacks available water, to the extent of hindering or preventing the growth and development of plant and animal life. Regions with arid climates tend to lack vegetation and are called xeric or desertic. Most ar ...
environment from the increased precipitation from the mountain range. As such, rivers that have headwaters in the mountains provide water for
irrigation Irrigation (also referred to as watering) is the practice of applying controlled amounts of water to land to help grow Crop, crops, Landscape plant, landscape plants, and Lawn, lawns. Irrigation has been a key aspect of agriculture for over 5,00 ...
in the surrounding lands. The need for water to irrigate prompted the construction of dams, which has been the source of several environmental concerns in the area. The northern end of the range is more arid; hence, the
Yaqui River The Yaqui River (Río Yaqui in Spanish) (Hiak Vatwe in the Yaqui or Yoreme language) is a river in the state of Sonora in northwestern Mexico. It was formerly known as the Rio del Norte. Being the largest river system in the state of Sonora, th ...
, which drains that area, is an important source of irrigation in the state of Sonora. The Yaqui drains into the
Gulf of California The Gulf of California ( es, Golfo de California), also known as the Sea of Cortés (''Mar de Cortés'') or Sea of Cortez, or less commonly as the Vermilion Sea (''Mar Bermejo''), is a marginal sea of the Pacific Ocean that separates the Baja Ca ...
, as do the
Humaya River The Humaya River is a river in the state of Sinaloa, Mexico, that connects to the Tamazula River in the city of Culiacán to form the Culiacán River. The source of the river is the Sierra Madre Occidental mountains. The water flows from the no ...
in Sinaloa and the
Fuerte River The Fuerte River is a river in the state of Sinaloa, in northwestern Mexico. It flows from headwaters in the Sierra Madre Occidental to the Pacific Ocean in the Gulf of California. Course It begins at the junction of the Rio Verde (also called ...
further south. The
Río Grande de Santiago The Río Grande de Santiago, or Santiago River, is a river in western Mexico. It flows westwards from Lake Chapala via Ocotlán through the states of Jalisco and Nayarit to empty into the Pacific Ocean. It one of the longest rivers in Mexico, ...
drains from the southern slopes of the Sierra Madre. Along the more arid eastern slopes of the mountains, the
Nazas River The Nazas River is a river located in northern Mexico, in the states of Coahuila and Durango. It is part of the endorheic Bolsón de Mapimí. It is only long, but irrigates an area of in the middle of the desert. The Nazas is also nurtured by t ...
and
Aguanaval River The Aguanaval River is a river located in northeastern Mexico. Geography It originates in the southern Sierra Madre Occidental range of Zacatecas state, and flows generally north through Zacatecas and Durango states to empty into the endorheic B ...
drain the mountains into a closed basin. These mountains supply 90% of the water used for irrigation within the watershed. North of this system is the
Conchos River The Río Conchos (Conchos River) is a large river in the Mexican state of Chihuahua. It joins the Río Bravo del Norte (known in the United States as the Rio Grande) at the town of Ojinaga, Chihuahua. Description The Rio Conchos is the main riv ...
which drains into the
Rio Grande The Rio Grande ( and ), known in Mexico as the Río Bravo del Norte or simply the Río Bravo, is one of the principal rivers (along with the Colorado River) in the southwestern United States and in northern Mexico. The length of the Rio G ...
. Along many rivers the arid conditions have caused courses to be
dam A dam is a barrier that stops or restricts the flow of surface water or underground streams. Reservoirs created by dams not only suppress floods but also provide water for activities such as irrigation, human consumption, industrial use ...
med to provide water for irrigation. These dams have caused concerns along with those caused by other activities. The Yaqui has been dammed with three large reservoirs along its course. The Río Grande de Santiago has also been dammed, including the Aguamilpa Dam begun in 1991 and the
El Cajón Dam (Mexico) The El Cajón Dam is a hydroelectric dam on the Río Grande de Santiago in the Mexican state of Nayarit. Construction began in 2003 and was completed in June 2007. It cost US$800 million to build. It is long and is high. The reservoir holds a ...
upstream from it. To provide irrigation water for farming the dry basin, the Nazas river was dammed in the 1930s and 1940s. This has led to the former drainage lakes in the area drying up, and
soil depletion Soil fertility refers to the ability of soil to sustain agricultural plant growth, i.e. to provide plant habitat and result in sustained and consistent Crop yield, yields of high quality.
from the elimination of the river as a source of soil. Due to the continued
logging Logging is the process of cutting, processing, and moving trees to a location for transport. It may include skidding, on-site processing, and loading of trees or logs onto trucks or skeleton cars. Logging is the beginning of a supply chain ...
in the area,
erosion Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is distin ...
on the slopes of hillsides has increased.


Human

Numerous small populations live in Copper Canyon, some of them around old missions. Many settlements consist of single families or small family groups near agricultural fields. There are also a few towns of note, including
Creel, Chihuahua Creel () is a town in the Sierra Tarahumara (part of the Sierra Madre Occidental) of the Mexican state of Chihuahua. It is the second-largest town (after San Juanito) in the municipality of Bocoyna. It is located some to the southwest of the ...
, with 5,000 inhabitants; it serves as a stop on the train line. South of Copper Canyon is the town of
El Salto, Durango El Salto is a town and seat of the municipality of Pueblo Nuevo in the southwestern part of the Mexican state of Durango. As of 2015, the town had a total population of 24,241, Situated on a pine-forested plateau about 2,580 meters (8,464 fee ...
, situated along highway 40. To the west is
Copala, Sinaloa Copala, formerly known as San José de Copala, is a four-century-old silver-mining town in the Mexican state of Sinaloa. The town is in the municipality of Concordia. History The area was occupied and ruled by the indigenous peoples until 156 ...
. To the south live the indigenous Cora people in the towns of Jesús María and La Mesa del Nayar. In addition, 1,000 people live in the village of Huajimic in Nayarit. The
Bolaños River The Bolaños River is a river in Mexico flowing through the Sierra Madre Occidental, and a tributary of Rio Grande de Santiago. It has a length of 360 km and a watershed of about 10 000 square kilometers. Geography The river's origin is in ...
valley of Jalisco is populated with mining communities, such as San Martín de Bolaños, which has a population of around 3,000. Few paved roads cross the mountains, meaning that travel times can be long, even between cities that are relatively close. In the north, Mexico Federal Highway 16 connects
Hermosillo Hermosillo (), formerly called Pitic (as in ''Santísima Trinidad del Pitic'' and ''Presidio del Pitic''), is a city located in the center of the northwestern Mexican state of Sonora. It is the municipal seat of the Hermosillo Municipality, Her ...
, Sonora and La Junta, Chihuahua. In the mountains, the
La Entrada al Pacifico LA most frequently refers to Los Angeles, the second largest city in the United States. La, LA, or L.A. may also refer to: Arts and entertainment Music * La (musical note), or A, the sixth note * "L.A.", a song by Elliott Smith on ''Figure ...
Corridor is an incomplete road intended to connect
Los Mochis Los Mochis () is a coastal city in northern Sinaloa, Mexico. It serves as the municipal seat of the municipality of Ahome. As of the 2010 census, the population was 362,613, which was 61 percent of the municipality's population. Los Mochis is th ...
, Sinaloa and Chihuahua. Durango and Mazatlan are connected by highway 40, around 24 degrees north latitude.


Geology

The Sierra Madre Occidental is a high plateau of volcanic rock that is eroded in areas to reveal a basement composed of
plutonic Intrusive rock is formed when magma penetrates existing rock, crystallizes, and solidifies underground to form '' intrusions'', such as batholiths, dikes, sills, laccoliths, and volcanic necks.Intrusive RocksIntrusive rocks accessdate: March ...
and
sedimentary Sedimentary rocks are types of rock (geology), rock that are formed by the accumulation or deposition of mineral or organic matter, organic particles at Earth#Surface, Earth's surface, followed by cementation (geology), cementation. Sedimentati ...
rocks underlying the two groups of
extrusive Extrusive rock refers to the mode of igneous volcanic rock formation in which hot magma from inside the Earth flows out (extrudes) onto the surface as lava or explodes violently into the atmosphere to fall back as pyroclastics or tuff. In contra ...
volcanics. The lower of these groups is a series of volcanic rocks formed by
lava flows Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or un ...
. The surface of the plateau is made up of a second series of volcanic
ignimbrite Ignimbrite is a type of volcanic rock, consisting of hardened tuff. Ignimbrites form from the deposits of pyroclastic flows, which are a hot suspension of particles and gases flowing rapidly from a volcano, driven by being denser than the surro ...
s, covered mostly by clay rich organic
soil Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former te ...
s. Some
intrusion In geology, an igneous intrusion (or intrusive body or simply intrusion) is a body of intrusive igneous rock that forms by crystallization of magma slowly cooling below the surface of the Earth. Intrusions have a wide variety of forms and com ...
s in the area have deposited
ore Ore is natural rock or sediment that contains one or more valuable minerals, typically containing metals, that can be mined, treated and sold at a profit.Encyclopædia Britannica. "Ore". Encyclopædia Britannica Online. Retrieved 7 Apr ...
veins that are commercially viable. The landscape was shaped after rock placement. Rivers
cut Cut may refer to: Common uses * The act of cutting, the separation of an object into two through acutely-directed force ** A type of wound ** Cut (archaeology), a hole dug in the past ** Cut (clothing), the style or shape of a garment ** Cut (ea ...
valleys into the plateau, following folds in the rocks. Rocks have broken off of the slopes, forming rocky sides. The bedrock is covered by the clay rich soils, except in eroded areas, where water carries away deposits leaving a stony surface.


Geological history

The basement is thought to be Older North American basement, especially in the North, and a number of different accreted terranes, which are mostly covered by
Cenozoic The Cenozoic ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterised by the dominance of mammals, birds and flowering plants, a cooling and drying climate, and the current configura ...
volcanism. The northern extent of the Sierra Madre is the Cortés Terrane, although the northern extreme of this contains a small portion of the Carborca Terrane. Some of the northern end may also be underlain by a Precambrian basement placed around the same time as the
Grenville Orogeny The Grenville orogeny was a long-lived Mesoproterozoic mountain-building event associated with the assembly of the supercontinent Rodinia. Its record is a prominent orogenic belt which spans a significant portion of the North American continent, f ...
. Some of this area has a series of
Paleozoic The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon. The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838 by combining the Greek words ''palaiós'' (, "old") and ' ...
sedimentary sequences from a deep marine environment underlying it, considered by some to be part of the Cotes Terrane and by others to be
transported ''Transported'' is an Australian convict melodrama film directed by W. J. Lincoln. It is considered a lost film. Plot In England, Jessie Grey is about to marry Leonard Lincoln but the evil Harold Hawk tries to force her to marry him and she w ...
. In some areas, distinct sedimentary rocks can be identified by shallow-water
Silurian The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleozo ...
and Mississippian sedimentary rocks underlying deep-water Pennsylvanian and
Permian The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last period of the Paleoz ...
, which are divided by Mississippian
rhyolite Rhyolite ( ) is the most silica-rich of volcanic rocks. It is generally glassy or fine-grained (aphanitic) in texture, but may be porphyritic, containing larger mineral crystals (phenocrysts) in an otherwise fine-grained groundmass. The mineral ...
. The Permian clastics contain some
detrital Detritus (; adj. ''detrital'' ) is particles of rock derived from pre-existing rock through weathering and erosion.Essentials of Geology, 3rd Ed, Stephen Marshak, p G-7 A fragment of detritus is called a clast.Essentials of Geology, 3rd Ed, Stephen ...
rock that sit alongside low-grade metamorphosed sedimentary and volcanic rocks with serpentinite. South of the Cortes and Carborca Terranes is the San José de García Terrane, which is a combination of Cretaceous arc volcanics and volcaniclastics, which may be thrusting over the Cortes terrane. The southern part of the range is made up of the Guerrero Composite Terrane, a large body, which is actually a complex of five different subterranes, not all of them within the main body of the Sierra Madre. However, the terrane is mostly covered by volcanics and sedimentary deposits, so it is only visible where erosion has revealed it. The main subterranes of the Guerrero Composite Terrane that are within the Sierra Madre are the Tahue and Zihuatanejo terranes. Dividing the Guerrero Terrane from the rest of the Sierra Madre terranes is a boundary that is thought to represent the Early Cretaceous Arperos Basin, a
marine basin Marine is an adjective meaning of or pertaining to the sea or ocean. Marine or marines may refer to: Ocean * Maritime (disambiguation) * Marine art * Marine biology * Marine debris * Marine habitats * Marine life * Marine pollution Military ...
which separated the island arc that came to form the Guerrero terrane from the accretions that came to form the Sierra Madre terrane. It contains a lower formation made up of
pillow basalt Basalt (; ) is an 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 surface of a rocky planet or moon. More than 90% of a ...
s with pillow breccias, tuffs, and
shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especial ...
s underlying a group of
pelagic The pelagic zone consists of the water column of the open ocean, and can be further divided into regions by depth (as illustrated on the right). The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or w ...
limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...
s, oozes, and
turbidite A turbidite is the geologic deposit of a turbidity current, which is a type of amalgamation of fluidal and sediment gravity flow responsible for distributing vast amounts of clastic sediment into the deep ocean. Sequencing Turbidites wer ...
s. Covering the southern basement are sedimentary and
metamorphosed Metamorphic rocks arise from the transformation of existing rock to new types of rock in a process called metamorphism. The original rock (protolith) is subjected to temperatures greater than and, often, elevated pressure of or more, causi ...
sedimentary rocks containing
argillite :''"Argillite" may also refer to Argillite, Kentucky.'' Argillite () is a fine-grained sedimentary rock composed predominantly of indurated clay particles. Argillaceous rocks are basically lithified muds and oozes. They contain variable amounts ...
, limestone, volcanic schist,
slate Slate is a fine-grained, foliated, homogeneous metamorphic rock derived from an original shale-type sedimentary rock composed of clay or volcanic ash through low-grade regional metamorphism. It is the finest grained foliated metamorphic rock. ...
, and
greywacke Greywacke or graywacke (German ''grauwacke'', signifying a grey, earthy rock) is a variety of sandstone generally characterized by its hardness, dark color, and poorly sorted angular grains of quartz, feldspar, and small rock fragments or lit ...
which were exposed in the canyon of the Santiago River. Near these sediments late
Oligocene The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but the ...
to early
Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...
granite Granite () is a coarse-grained (phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies undergro ...
and
granodiorite Granodiorite () is a coarse-grained (phaneritic) intrusive igneous rock similar to granite, but containing more plagioclase feldspar than orthoclase feldspar. The term banatite is sometimes used informally for various rocks ranging from gra ...
intrusive bodies occur. A possible cause of this is that these bodies were roof pendants which were uplifted by
pluton In geology, an igneous intrusion (or intrusive body or simply intrusion) is a body of intrusive igneous rock that forms by crystallization of magma slowly cooling below the surface of the Earth. Intrusions have a wide variety of forms and com ...
s. Mesozoic limestone also occurs in northern portion of the mountains, mostly from the Cretaceous. Towards the end of the
Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...
, the
Laramide orogeny The Laramide orogeny was a time period of mountain building in western North America, which started in the Late Cretaceous, 70 to 80 million years ago, and ended 35 to 55 million years ago. The exact duration and ages of beginning and end of the ...
increased the activity of
magmatism Magmatism is the emplacement of magma within and at the surface of the outer layers of a terrestrial planet, which solidifies as igneous rocks. It does so through magmatic activity or igneous activity, the production, intrusion and extrusion of ...
in the area, forming the first major igneous series in the area. The igneous series are made up of formations of plutonic and volcanic rock, which would later be exposed.
Interbedded In geology, interbedding occurs when beds (layers of rock) of a particular lithology lie between or alternate with beds of a different lithology. For example, sedimentary rocks may be interbedded if there were sea level variations in their sedim ...
with these rocks are sedimentary deposit rocks. In the center of the range, some of these rocks have been deformed by tectonic forcing that occurred at the same time. The southern part of the range contains none of the volcanism that is apparent in the northern range. These formations ended in the
Paleocene The Paleocene, ( ) or Palaeocene, is a geological epoch (geology), epoch that lasted from about 66 to 56 mya (unit), million years ago (mya). It is the first epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), E ...
.
Eocene The Eocene ( ) Epoch is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene' ...
volcanism formed a series of
andesitic Andesite () is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained (aphanitic) to porphyritic in texture, and is composed predomin ...
and
rhyolitic Rhyolite ( ) is the most silica-rich of volcanic rocks. It is generally glassy or fine-grained (aphanitic) in texture, but may be porphyritic, containing larger mineral crystals (phenocrysts) in an otherwise fine-grained groundmass. The mineral ...
formations in the area, with spatial and temporal variations throughout. Most of the
gold Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile met ...
and
silver Silver is a chemical element with the Symbol (chemistry), symbol Ag (from the Latin ', derived from the Proto-Indo-European wikt:Reconstruction:Proto-Indo-European/h₂erǵ-, ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, whi ...
deposits are also in these rocks. In the Oligocene, ash flows became the predominant deposit of the area, with interbedded lava flows between. These ash flows began the second series of high magmatism formations. The
Mid-Tertiary ignimbrite flare-up The Mid-Tertiary ignimbrite flare-up, was a dramatic period of volcanic eruptions in mid-Cenozoic time, approximately 25–40 million years ago, centered in the western United States. These eruptions are seen today as deposits of ignimbrite, the ...
formed a series of ignimbrite formations, layered one atop another, that are sometimes broken by lava flows. The ignimbrite formations in this area cover the largest area of any known series, with ten
caldera A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcano eruption. When large volumes of magma are erupted over a short time, structural support for the rock above the magma chamber is ...
s identified in the province. Three of these calderas are in Copper Canyon. The lava has formed a series of
mafic A mafic mineral or rock is a silicate mineral or igneous rock rich in magnesium and iron. Most mafic minerals are dark in color, and common rock-forming mafic minerals include olivine, pyroxene, amphibole, and biotite. Common mafic rocks incl ...
rocks that comprise the Southern Cordilleran Basaltic Andesite Suite. The
tuff Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is lithified into a solid rock. Rock that contains greater than 75% ash is considered tuff, while rock cont ...
s are above a thick formation of lava rock. Around five or six units have been identified, mostly around the Copper Canyon area. These tuffs have allowed wide-ranging correlation with formations in other geographical areas, for example
Death Valley Death Valley is a desert valley in Eastern California, in the northern Mojave Desert, bordering the Great Basin Desert. During summer, it is the Highest temperature recorded on Earth, hottest place on Earth. Death Valley's Badwater Basin is the ...
. During the Miocene, three periods of volcanism marked separate events in the Sierras. Each period is marked by different volcanic processes. The first was a continuation of the Oligocene flare-up, which lasted through the early Miocene. This may be a distinct second occurrence of the same process, placing silica-rich lava above Oligocene rocks. Also in the early Miocene more intermediate
Basaltic andesite Basaltic andesite is a volcanic rock that is intermediate in composition between basalt and andesite. It is composed predominantly of augite and plagioclase. Basaltic andesite can be found in volcanoes around the world, including in Central Amer ...
s occur along faults and in grabens. Beginning in the early Miocene and continuing into the middle, an arc of andesite was placed during the spreading of the
Gulf of California The Gulf of California ( es, Golfo de California), also known as the Sea of Cortés (''Mar de Cortés'') or Sea of Cortez, or less commonly as the Vermilion Sea (''Mar Bermejo''), is a marginal sea of the Pacific Ocean that separates the Baja Ca ...
. The basin and range-style faulting of the middle-late Miocene took place at the same time as the placement of
alkali basalt Alkali basalt or alkali olivine basalt is a dark-colored, porphyritic volcanic rock usually found in oceanic and continental areas associated with volcanic activity, such as oceanic islands, continental rifts and volcanic fields. Alkali basalt ...
s, In the westernmost slopes mafic dikes formed. These events have also been linked to the subduction of the
Farallon Plate The Farallon Plate was an ancient oceanic plate. It formed one of the three main plates of Panthalassa, alongside the Phoenix Plate and Izanagi Plate, which were connected by a triple junction. The Farallon Plate began subducting under the west ...
. Episodes of volcanism continued into the
Quaternary The Quaternary ( ) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS). It follows the Neogene Period and spans from 2.58 million years ...
.


Structures

The Sierras are believed to be a thick core covered by volcanics and eroded by numerous rivers. Some have suggested that the basement of the mountains have numerous intrusions made by mafic
magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma is found beneath the surface of the Earth, and evidence of magmatism has also been discovered on other terrestrial planets and some natural sa ...
. At their surface, the mountains are made up of large-scale ignimbrite sheet that has been incised by rivers flowing from rainfall in the mountains. The surface of the plateau is almost exclusively from the second series of flows causing the rock that is most visible to be ignimbrites with lava flow layers. The region has a general Strike and dip, strike from just west of north to just south of east. Fault (geology), Faults in the area tend to be younger than the upper volcanics, excluding those associated with calderas, but do occur in distinct periods. The large faults along the eastern slope have caused the slope to be made up of large escarpments that face into the interior Structural basin, basins. These faults are commonly covered by alluvium and basalt, making them difficult to discern, but can be found in certain fault blocks. Grabens have formed in the north, and some of these are filled with volcanic and sedimentary floors, and long Depression (geology), depressions have formed in the southern Sierra Madre. The faulting decreases in the center of the range where the faults are mostly small Dip-slip faults, normal faults, but increases once again on the western slope. In fact, the major normal faults tend to diverge around the center of the core and join at either end. Some of these faults may have allowed ignimbrites to Fissure vent, erupt from the surface, and so there may be some association between the ignimbrite occurrence and faults; this can be used to find out Structural geology, information about different kinds of basement rock present. There are two faults dividing the Sierra Madre from the central Mexican Plateau. The more southern one is the north–south Aguascalientes fault extending from Altos de Jalisco to near Zacatecas, where it joins the more northern northwest–southeast trending San Luis–Tepehuanes fault extending from Guanajuato to Durango. The southern boundary of the Sierra Madre Occidental with the Jalisco block is a series of folds, Thrust fault, thrust, and left Strike-slip fault, lateral faults date from the middle Miocene. This may be evidence for a left transpressional shear zone. The area between this boundary and the Aguascalientes fault is filled with numerous grabens and half-grabens, as well an east–west left shear zone, the El Roble shear zone. At the west end of these grabens and half-grabens are the Pochotitan and the more northerly San Pedro fault systems, which form the western boundary of the faults in the southern mountains. In the north there is an unknown boundary between the Cortes Terrane and the Guerrero Composite Terrane. Some theorize that this is a section of the Mojave–Sonora Megashear, but this theory is not universally accepted; however, the Megashear is important, and, in fact, is necessary for Historical Geology, reconstructions of the opening of the Gulf of California, as of 2003.


Mineral deposits

On a smaller scale, mineral deposits are distributed in formations of the Sierra Madre, although the Ore genesis, events that placed these deposits vary throughout the mountains. The Guerrero composite terrane contains many of the economic deposits, often found in ore bodies younger than the Cretaceous. Gold and silver deposits most commonly occur in the altered andesites of the early volcanics, typically these deposits are between 30 and 50 million years old. These are believed to be caused by later
intrusion In geology, an igneous intrusion (or intrusive body or simply intrusion) is a body of intrusive igneous rock that forms by crystallization of magma slowly cooling below the surface of the Earth. Intrusions have a wide variety of forms and com ...
s into the early flows. Fissure-vein deposits have been divided into two groups of Fracture (geology), fissure Vein (geology), vein deposits, which are divided geographically into an eastern and western series. In the east, the gold and silver are accompanied by lead and zinc. In the south, the Bolaños Municipality, Bolaños mine district is contained with the Bolaños Graben. Some also occur as epithermal deposits. Also, some gold occurs along with copper in Cenozoic iron-oxide Skarn#Ore deposits, skarn and replacement deposits along the Pacific. In addition to gold and silver and their related deposits, tin, iron, and Mercury (element), mercury occur, sometimes in later units, mostly in later volcanics, and Molybdenum occurs in the mountains, often along with older copper deposits or in Oligocene deposits in the east. The belt of tin deposits lies mostly within the eastern slopes from Durango to Guanajuato. In these areas, tin occurs in rhyolitic ignimbrites in many, possibly over 1000, small deposits of cassiterite. Typically these deposits are divided from overlying ignimbrites by breccia, which may also contain ore. Many of these are thought to be Epithermal, hydrothermal deposits To the east of these units is a belt of more mercury deposits, followed by another belt of manganese deposits, although these deposits are mostly limited to Chihuahua and Hidalgo. Iron occurs in three different regions placed by different mechanisms. Along the Pacific there the numerous skarn and replacement deposits mentioned above with relation to gold. Iron occurs in Durango in the form of magnetite lava flows, which are often surrounded by smaller hematite deposits, thought to be ash flows. There is also a belt of iron deposits further east.


Soil

Most soil in the mountains is covered by an Organic matter, organic-rich layer over layers rich in clay. Soils are commonly phaeozems that are up to . Some soils are cambisols that are less than deep and well-Drainage, drained. Due to the high clay content, which blocks water from being absorbed into the soil, larger rock particles in the soil help reduce runoff and soil losses from erosion. Areas that are covered in stone are known as lithosols, and make up most of the remaining surface in the mountains, especially on upper slopes. The last major soil type are vertisols, which are thin mineral-poor soils. Soils at higher elevations experience more Leaching (pedology), leaching, due to increased rainfall. Acidic soils may have lower calcium content, leading to lower plant soil quality. Soils along the eastern slopes have increased organic content and a clay heavy layer that is developed more than those of the more arid eastern lands. The thickness of soil layers also increases. Problems with soil degradation have been aggravated by the cultivation of drug crops, leading to deforestation of many areas. Other problems include overgrazing, which has led to terracing from cattle paths and the formation of a soil crust, and soil acidification, which poses a risk to some grasslands as of 2002.


Climate

The climate varies considerably between the northern and southern extents of this long mountain range. Seasonal variations also occur due to the presence of large bodies of warm water delivering warm damp air from each side of the range. This region undergoes a seasonal variety with two wet seasons, including a summer monsoon, and two dry seasons each year.


Temperature, pressure, and wind

Air pressure changes in northwestern Mexico and the southwest United States are the main causes of seasonal variation in the Sierra Madre. A high pressure area that rests over the mountains in the winter begins to move north of the mountains into New Mexico during the month of June. The high pressure begins to break down and move south during September or October; however, the breakdown is usually at a slower pace than the movement north. This high pressure belt is associated with the mechanics that form the Bermuda High. The climate in the mountains is mild. Summer temperatures maintain a constant level. Maximum temperatures are typically in July at around 31 C with average temperatures of the order of 16 C during this same period. Mean annual temperatures are between above . Below-freezing temperatures can occur in the higher mountains, with precipitation (meteorology), precipitation occurring as snowfall certain times of year. During the summer monsoon, wind patterns undergo large-scale changes. In May there is very little large-scale wind current through the mountains, most circulates around the mountains, although Sea breeze, onshore flow is present. As the high pressure moves north, air is pulled off the Gulf of Mexico, bringing easterly winds aloft to the mountains. On the east slope of the mountain, daytime upslope winds flow to the crest, where the flow joins westerly winds. The mountains cause convection during the following monsoon season, during which nocturnal winds at low levels in the atmosphere move moisture overnight. Extensive lightning activity occurs during this season. After the high pressure breaks down, wind patterns return to those prior to the monsoon season.


Precipitation and humidity

Precipitation varies on both annual and seasonal scales in the Sierra Madre. Annual differences in regional climate are associated with the El Niño-Southern Oscillation with El Niño years leading to a wetter climate. Monsoon rains come to the Sierra Madre in June as the high pressure area moves north, leading to wet summer seasons. This causes east winds bringing moisture from 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 ...
. On the western side of the mountains, which are affected by the largest change in precipitation between the dry season and monsoon season, in the monsoon season rainfall can exceed in a single month. The southern region receives more of the rainfall than the northern. Much of this precipitation occurs as tropical storms. As the high pressure over New Mexico breaks down, rainfall in the Sierra Madre ends. Because of the monsoon, the summer accounts for the majority of rainfall in the area. The spring and fall dry season separate out a weaker wet season in the winter. In addition to increasing in the southern ranges of the mountains, rainfall increases in the higher elevations of the Sierra Madre Occidental. Humidity in the mountains varies at wide levels as does rainfall. In the early morning before dawn, the air is almost saturated (often over 90% relative humidity) near the mountain tops with low clouds over the range. Lower in the range, air is not as near saturated in the morning. Seasonal variation in humidity is also present with average May and June relative humidity around 50%, with 25% possible during the day. Also during the day, relative humidity drops and cloud levels rise as temperatures rise. The humidity of the range is also influenced by the same seasonal changes as rainfall. In the dry season dew points are low at high elevations (500 hPa), around in the south of the range, and in the north in May. In June, dew points begin to increase from the May levels up to in the north and in the south. By July these dew points are at throughout the range. The range allows higher dew points throughout these periods than the surrounding low lands. This rise in humidity accompanies the monsoon.


Ecology

The mountains create a diverse setting for plants and animals by creating a different set of conditions from the surroundings. The Sierra Madre Occidental pine-oak forests are found at elevations of throughout the range, but the forests in the mountains vary by elevation and place in the range. This ecoregion is noted for its high biodiversity and large number of Endemism, endemic species, and for allowing some species to extend their Range (biology), range.


Flora

The Dominance (ecology), dominant plants vary across the range, and the habitat that they present varies from scattered woodland to both deciduous and Pinophyta, coniferous forest. The elevation and latitude in the range are the major determining factors in the dominant plants. Oaks dominate the lower reaches of the mountains, where stands grow down to about . Some oak species even continue into the surrounding ecosystems. In the western slopes of the range, cloud forest also occurs, mostly on mid-elevation slopes with little exposure to wind or sun in the southern end of the range. At higher elevations pines begin to grow alongside the oaks, and pines begin to dominate the oaks at higher elevations. At high elevations and in the north, Temperate broadleaf and mixed forest, mixed conifer forests become the dominant ecosystem. These forests are composed primarily of pines and firs, which begin to grow at these elevations. There are also Alpine tundra, grasslands on some mountain tops, surrounded by the forest that occur in those areas. Plants in the area typically have large responses to the change in climate with each season. Monsoon season is the largest of these effects, with leaf buds following only a few months after the rains begin. Flowering season occurs in the months preceding the summer monsoon. This is only the peak flowering season, with plants flowering throughout the year. Due to the early flowering, fruit is ripe and seeds are dispersed at the beginning of the rains. There are also areas where plants have little response to the seasons, particularly those areas that experience moist conditions, caused by the elevations. These plants may maintain leaves through times when other areas are in the dry season, during which most deciduous trees have no leaves.


Fauna

The mountains are often a Habitat corridor, corridor for species allowing more diversity in the area, by combining species from different regions. Animals typically associated with arid and mountainous habitats share the mountains with species associated with habitats further south. There are many carnivorous and omnivorous mammals native to the area, although several are extirpated or are part of threatened populations. The Mexican wolf's range in the mountains is limited to the foothills of Durango or the animal may have been extirpated; the black bear population is small, and the Mexican grizzly bear that once resided here is confirmed extinct. North American jaguar, Jaguars and ocelots are also now rare. On the other hand, North American cougar, mountain lion and bobcat are more common. On the eastern slopes there are American badger, coyote and gray fox that live across the mountains. Native ungulates include the white tailed deer, mule deer, and collared peccary. Rodents and lagomorphs include the eastern cottontail, which lives in the forests of the western slopes, cliff chipmunk, rock squirrel, Mexican fox squirrel, and various species of Cricetidae. Raccoons, hog-nosed skunk, and hooded skunk live in the mountains. The white-nosed coati lives on the western slopes, and the ring-tailed cat lives throughout. Many species of bats live in the mountains also. A variety of lizards live in the area and surroundings. The Tarahumara frog lives in the oak and pine stands preferring moving water to pools. The southern extent of the Lampropeltis knoblochi, Sonoran mountain kingsnake's range is the Chihuahuan desert into the mountains. Other snakes and frogs live in the mountains, and many species live in the western slopes. Birds frequent the mountains, some as a Bird migration, migratory path and others as Indigenous (ecology), native species. The migratory birds often use the area to the west as an overwintering area, and migrate north along the western slopes. In the northern canyons birds may be divided into different habitats, or more specifically, the different types of forest, leading to differences in range by elevation. Some of this difference by elevation may even extend the range of some species, enabling Tropics#Ecosystems, tropical species to use the mountain valleys for migration. Bird species endemism, endemic to the Sierra Madre Occidental include tufted jay, the "gray-eared" subspecies of red warbler, eared quetzal, thick-billed parrot, and formerly included the imperial woodpecker, which now may be extinct. The rivers and streams of the range contain some of the southernmost trout populations in North America. These populations may be native, although this is not universally accepted. Invasive species, Invasive fish compete with the native species which has been a cause of concern among researchers, along with concerns about the effects of logging on these species.


Surroundings

The Sonoran Desert is found in the northwestern foothills at . The Chihuahuan Desert is found to the northeast and east, the Meseta Central matorral and Central Mexican matorral to the southeast, and the Sinaloan dry forests to the west and southwest. These lower elevations are usually graded into by a stand of Tropical and subtropical dry broadleaf forests, tropical deciduous forest, which has a large portion of flora made up of flowering plants and legumes. These flowering plants are mostly from the genus ''Bursera''. The ecotone, made up of the tropical deciduous forest, is commonly sparsely populated, sometimes only by small stands of trees. It may be referred to as Oak savanna, savanna.


Preservation

Conservation (ethic), Preservation efforts in the modern day include those of Edwin Bustillos. Other groups, including Conservation International, work to protect animal species in the area. Basaseachic Falls National Park is a List of national parks of Mexico, national park in the mountains containing the highest waterfalls in the country. Cumbres de Majalca National Park was designated in 1939. Additionally, there are reserves such as La Michilía in the southern Sierra Madre, or the Tutuaca reserve in western Chihuahua, which was established in 2000 under a new system of management. Other protected areas in the Sierra include the Bavispe Flora and Fauna Protection Area, Bavispe, Campo Verde Flora and Fauna Protection Area, Campo Verde,
Cerro Mohinora Cerro Mohinora is an extinct volcano that is part of the Sierra Madre Occidental mountain range in the Mexican state of Chihuahua (state), Chihuahua located in the municipality of Guadalupe y Calvo. Cerro Mohinora is the highest point in the stat ...
, Papigochic Flora and Fauna Protection Area, Papigochic, and Sierra de Álamos–Río Cuchujaqui flora and fauna protection areas. The Cuenca Alimentadora del Distrito Nacional de Riego 043 Estado de Nayarit, established in 1949 to protect forests and watersheds, is now a natural resources protection areas of Mexico, natural resources protection area which conserves much of the southern Sierra.


People and history

The mountains are home to several indigenous nations speaking Uto-Aztecan languages, including the Tarahumara in the central portion of the range, the Huichol people, Huichol in the southern part of the range, and the Tepehuanes in the eastern slopes.


Prehistory

Archaic period in the Americas, Archaic cultures are known to have inhabited the Sierra Madre along with the rest of the surrounding lands, but little is known of the culture, although it does vary between the northern and southern extremes of the range. The Agriculture in Mesoamerica, agrarian Chalchihuites, Chalchihuites Culture began as farming communities around the first century AD and remained small communities until 300 AD when new agricultural techniques caused a large growth in population until around 500 AD. This culture began to decline in the ninth century. The Mogollon culture has been described in the northern foothills. Sites date the emergence of the culture to around 900 AD, and its abandonment to around 1000–1100 AD. During the Mesoamerica#Postclassic, period estimated for Mogollon abandonment, the Rio Sonora culture began Agriculture in Mesoamerica, agricultural developments along the Rio Sonora and rivers flowing into it. This culture produced pottery and lived in Pit-house, pit houses, until 1150 to 1200 when they began to construct surface dwellings. Construction of these houses ended around AD1550.


Spanish Sierra Madre

Francisco de Ibarra came to Durango in 1554, and began to settle the area. He would explore the western coast and cross the Sierra Madre in 1564. Early Spanish influence in the area came from the new silver mines, the first of which was established in 1567 at Santa Barbara. As sites opened for mining, Mission (Christianity), missionaries came to the areas and had a strong presence by 1595. The first meeting with the Tarahumara came in 1607, when a missionary went up the valley to meet them. Opposition to the missionaries built up, leading to the Tepehuán Revolt. This revolt began in 1616 in the town of Santa Catarina de Tepehuanes in Durango, and lasted for two years. The discovery of silver at Parral, Chihuahua, Parral in 1631 led to the northern limit of settlement moving into Tarahumara lands. The Society of Jesus, Jesuits renewed missionary activity in the 1630s, with a new program that increased in scope until around 1650. Tarahumara moved further into the mountains in order to escape the conditions. A Native American disease and epidemics#European contact, smallpox epidemic caused a revolt in 1645. A revolt arose in 1648, primarily among the Tarahumara. A drought caused a pair of revolutions in 1650 and 1652. The last major revolt began in March 1690 among the Tarahumara and ended in 1698. Demands from Conscription, labor drafts increased in the 1720s, placing a new pressure on missions. Criticism of the Jesuits rose in the 1730s with complaints of Jesuit Commerce, which was established by mission stores. In 1767, Jesuits were Suppression of the Society of Jesus, expelled from New Spain, ending the mission program. A new colonial official, José de Gálvez, came to New Spain and established new laws that caused a boom in silver mining activity in the 1770s. After the Apache faced heightened resistance to raiding from the Spanish in Chihuahuan, they moved down to the Sierra Madre in 1794. By 1800, raiding had essentially ended.


Mexican Sierra Madre

After leaving San Carlos in the fall of 1881, Geronimo and other Apache moved to the mountains, and became known as the ''Nednai'', sometimes referred to as the "Pinery Apache" or "Bronco Apache". From there they raided Sonora and the surrounding land until General George Crook entered the mountains in 1883 to discuss Geronimo's return. Geronimo eventually surrendered in 1886. Pancho Villa fled to the mountains in 1894, becoming a bandit.


19th century

Railroads came to the area starting in the 1880s and 1890s, which allowed many old mines in the region to reopen at a profit. Since most of the railroads were American, the foreign influence led to unrest among the people living in the mountains, causing the Tomochic rebellion in 1892. In addition to the railroads, canals were constructed in the 1890s in the Yaqui and Mayo river valleys. These canal projects failed, however, owing to the resistance that the natives of the valleys put up against the projects. Loggers began arriving in the mountains in the late 1800s. In response to the new industry, the Tarahumara moved further into the canyons.


20th century

The Mexican Revolution, 1910 revolution began in Chihuahua and spread over the mountains throughout the winter of 1910–1911. Silver mines were forced to make payments to the rebels, but were allowed to continue operating. General John J. Pershing began to follow Pancho Villa in 1916 and entered the mountains; however, he received no information from the local population. The raids subsided by 1919, and Villa returned peacefully to the foothills. In order to construct irrigation projects in the lowlands below the valleys, irrigation projects were never completed in the Sonoran hills; instead, the Yaqui River was dammed in the 1930s. Dams continued to be constructed in the 1940s and 1950s on the Yaqui River and its tributaries with the largest reservoir, behind the Álvaro Obregón Dam completed in 1952. Dams were also constructed on the Mayo river. Because of the dams, soil condition deteriorated, and more work was required to improve soil quality. The mountain range was crossed by the Ferrocarril Chihuahua al Pacifico Rail transport, railroad, completed in 1961. The railroad went up for sale in 1996, but no transaction was ever completed.


See also

* List of birds of the Sierra Madre Occidental * Sierra Madre (disambiguation), Sierra Madre * Sierra Madre Occidental pine-oak forests *
Sierra Madre Oriental The Sierra Madre Oriental () is a mountain range in northeastern Mexico. The Sierra Madre Oriental is part of the American Cordillera, a chain of mountain ranges (cordillera) that consists of an almost continuous sequence of mountain ranges that f ...


References


External links

* {{Authority control Sierra Madre Occidental, Landforms of Aguascalientes Landforms of Chihuahua (state) Landforms of Durango Landforms of Guanajuato Landforms of Jalisco Landforms of Nayarit Landforms of Sinaloa Landforms of Zacatecas Mountain ranges of Mexico, Madre Occidental Mountain ranges of Sonora Mountain ranges of the Sonoran Desert North American Cordillera Pacific Coast of Mexico Physiographic provinces Physiographic regions of Mexico Volcanism of Mexico