Misplaced Pages

#245754

88-718: The river flows from the Sierra Madre Occidental headwaters confluence generally westwards and down into the Gulf of California of the Pacific Ocean. This article about a location in the Mexican state of Sinaloa is a stub . You can help Misplaced Pages by expanding it . This article related to a river in Mexico is a stub . You can help Misplaced Pages by expanding it . Sierra Madre Occidental The Sierra Madre Occidental

176-622: A marine basin 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 basalts with pillow breccias , tuffs, and shales underlying a group of pelagic limestones , oozes , and turbidites . Covering the southern basement are sedimentary and metamorphosed sedimentary rocks containing argillite , limestone, volcanic schist , slate , and greywacke which were exposed in

264-416: A source of water , in an otherwise arid environment from the increased precipitation from the mountain range. As such, rivers that have headwaters in the mountains provide water for irrigation 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,

352-495: A " chubasco " can cause significant damage to shorelines, despite their brevity. The depth of the water helps to determine its temperature. For example, shallow depths are directly influenced by the local temperature of the air, while deeper waters are less susceptible to changes in air temperature. The temperature of the water in the gulf generally experiences lows of 16 °C (61 °F) in winter and highs of 24 °C (75 °F) in summer. But temperatures can vary greatly in

440-448: 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 to live, until Spanish settlers with associated mestizos came into the area to found towns for the silver mines in the area. The major industries in the area now are agriculture and forestry, which have become contentious because of land degradation and

528-500: A few towns of note, including Creel, Chihuahua , with 5,000 inhabitants; it serves as a stop on the train line. South of Copper Canyon is the town of El Salto, Durango , situated along highway 40. To the west is Copala, Sinaloa . 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 valley of Jalisco

616-506: A mean depth of 818.08 m (2,684.0 ft), and a volume of 145,000 km (35,000 cu mi). The Gulf of California is divided into three faunal regions: Northern, Central, and Southern. One recognized transition zone is termed the Southwestern Baja California peninsula. Transition zones exist between faunal regions, and they usually vary for each individual species. (Faunal regions are distinguishable based on

704-416: A number of negative estuaries , that is, ones in which the evaporation of seawater is relatively greater than that of the fresh water input. The salinities of these inlets are higher than that of the ocean. The temperatures, poikilothermal , of these negative estuaries also are higher than the general temperature of the gulf. It is possible that at one time these estuaries were positive, that is, ones in which

792-617: A series of Paleozoic 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 . In some areas, distinct sedimentary rocks can be identified by shallow-water Silurian and Mississippian sedimentary rocks underlying deep-water Pennsylvanian and Permian , which are divided by Mississippian rhyolite . The Permian clastics contain some detrital rock that sit alongside low-grade metamorphosed sedimentary and volcanic rocks with serpentinite. South of

880-611: A series of folds, thrust , and left 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

968-567: A smaller scale, mineral deposits are distributed in formations of the Sierra Madre, although the 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 intrusions into

SECTION 10

#1733085732246

1056-435: A summer monsoon , and two dry seasons each year. 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,

1144-407: 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 . 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

1232-599: A whole were enacted as "Area Reserve and Migratory Bird Refuge and Wildlife" on August 2, 1978. In June 2000, the islands were designated a flora and fauna protection area . In addition to this effort by the Mexican government, for its importance and recognition worldwide, all islands in the gulf are also part of the international program "Man and Biosphere" (MAB) and are part of the World Reserve Network UNESCO Biosphere as Special Biosphere Reserve. Because of

1320-409: Is a high plateau of volcanic rock that is eroded in areas to reveal a basement composed of plutonic and sedimentary rocks underlying the two groups of extrusive volcanics. The lower of these groups is a series of volcanic rocks formed by lava flows . The surface of the plateau is made up of a second series of volcanic ignimbrites , covered mostly by clay rich organic soils . Some intrusions in

1408-735: Is a major mountain range system of the North American Cordillera , that runs northwest–southeast through northwestern and western Mexico, and along the Gulf of California . The Sierra Madre is part of the American Cordillera , a chain of mountain ranges (cordillera) that consist of an almost continuous sequence that form the western "sounds" of North America , Central America , South America , and West Antarctica . The Spanish name sierra madre means "mother mountain range" in English, and occidental means "western", these thus being

1496-423: Is also a belt of iron deposits further east. Most soil in the mountains is covered by an organic -rich layer over layers rich in clay . Soils are commonly phaeozems that are up to 100 centimetres (39 in). Some soils are cambisols that are less than 2 metres (6.6 ft) deep and well- drained . Due to the high clay content, which blocks water from being absorbed into the soil, larger rock particles in

1584-553: 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

1672-456: 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 andesites occur along faults and in grabens. Beginning in the early Miocene and continuing into

1760-627: Is often referred to as the Gulf of California Rift Zone . The Gulf would extend as far as Indio, California , except for the tremendous delta created by the Colorado River . This delta blocks the sea from flooding the Mexicali and Imperial Valleys . Volcanism dominates the East Pacific Rise . The island of Isla Tortuga is one example of this ongoing volcanic activity. Furthermore, hydrothermal vents due to extension tectonic regime, related to

1848-645: 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 , Sonora and La Junta, Chihuahua. In the mountains, the La Entrada al Pacifico Corridor is an incomplete road intended to connect Los Mochis , Sinaloa and Chihuahua. Durango and Mazatlán are connected by highway 40 , around 24 degrees north latitude. The Sierra Madre Occidental

SECTION 20

#1733085732246

1936-480: Is responsible for 56 islands located off the coast of the state. These are grouped into four archipelagos: San Luis Gonzaga or Enchanted, Guardian Angel, Bahía de los Ángeles and San Lorenzo. The three general types of shores found in the gulf include rocky shore , sandy beach, and tidal flat. Some of the rich biodiversity and high endemism that characterize the gulf and make it such a hotspot for fishing can be attributed to seemingly insignificant factors, such as

2024-832: The Aguamilpa Dam begun in 1991 and the El Cajón Dam 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 from the elimination of the river as a source of soil. Due to the continued logging in the area, erosion on the slopes of hillsides has increased. 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

2112-652: The Grand Canyon . This plateau has an average elevation of 2,250 m (7,380 ft) 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 , located at 25°57′N 107°03′W  /  25.950°N 107.050°W  / 25.950; -107.050 . Estimates for

2200-438: The Gulf of Mexico . 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 300 mm (12 in) 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

2288-722: The Nazas River and Aguanaval River 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 which drains into the Rio Grande . Along many rivers the arid conditions have caused courses to be dammed 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

2376-628: The Sea of Cortés ( Mar de Cortés ) or Sea of Cortez , or less commonly as the Vermilion Sea ( Mar Vermejo ), is a marginal sea of the Pacific Ocean that separates the Baja California peninsula from the Mexican mainland. It is bordered by the states of Baja California , Baja California Sur , Sonora , and Sinaloa with a coastline of approximately 4,000 km (2,500 mi). Rivers that flow into

2464-596: The Sierra Madre del Sur and the Eje Volcánico Transversal (Transverse Volcanic Axis) of central Mexico after crossing 1,250 km (780 mi). The mountains range from 300 km (190 mi) from the Gulf of California in the north, but begin to approach within 50 km (30 mi) of the Pacific in the south. These mountains are generally considered to be part of the much larger American cordillera ,

2552-507: The United States Fish Commission visited the area. The International Hydrographic Organization defines the southern limit of the gulf as: "A line joining Piaxtla Point (latitude 23°38'N) on the west coast of the mainland of Mexico, and the southern extreme of Lower California". The gulf is 1,126 km (700 mi) long and 48–241 km (30–150 mi) wide, with an area of 177,000 km (68,000 sq mi),

2640-616: The Yaqui River , which drains that area, is an important source of irrigation in the state of Sonora. The Yaqui drains into the Gulf of California , as do the Fuerte River in Sinaloa and the Humaya River further south. The Río Grande de Santiago drains 100,000 km (39,000 sq mi) from the southern slopes of the Sierra Madre. Along the more arid eastern slopes of the mountains,

2728-428: 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

Culiacán River - Misplaced Pages Continue

2816-447: The seawater component is diluted; therefore, the water is brackish , with salinity less than that of the ocean. However, because of human settlement around the gulf and water diversion for municipal and agricultural use in an area of comparatively low rainfall, there are no longer many rivers that freely empty into the gulf. The upper Colorado River Delta is one example of a historically major estuary and wetlands ecosystem, that since

2904-787: The "Western mother mountain range". To the east, from the Spanish oriental meaning "eastern" in English, the Sierra Madre Oriental range or "Eastern mother mountain range" runs generally parallel to the Sierra Madre Occidental along eastern Mexico and the Gulf of Mexico . The range extends from northern Sonora , a state near the Mexico–U.S. border at Arizona , southeast towards to the Trans-Mexican Volcanic Belt and Sierra Madre del Sur ranges. The high plateau that

2992-495: The 20th century construction of upriver dams and diversion aqueducts on the Colorado River, is now a small ephemeral remnant estuary. The remaining gulf inlets still are important to several species of fishes, crustaceans, and shellfish that are commercially harvested. Even though the shores of the gulf are generally sheltered from the continuous wave shock that is experienced by most other North American shores, storms known as

3080-576: 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,

3168-544: The Gulf of California are a UNESCO World Heritage Site . The marine expeditions of Fortún Ximénez , Hernán Cortés , Juan Rodríguez Cabrillo , Francisco de Ulloa , Hernando de Alarcón , Captain Francisco de Lucenilla, and Sebastián Vizcaíno document its earliest record. Juan de Oñate reached the gulf overland in 1605 by following the Colorado River . In the 19th century Duflot de Mofras of France and C.H. Gilbert of

3256-527: The Gulf of California include the Colorado , Fuerte , Mayo , Sinaloa , Sonora , and the Yaqui . The surface of the gulf is about 160,000 km (62,000 sq mi). Maximum depths exceed 3,000 meters (9,800 ft) because of the complex geology, linked to plate tectonics . The gulf is thought to be one of the most diverse seas on Earth and is home to more than 5,000 species of micro-invertebrates. Parts of

3344-638: The North, and a number of different accreted terranes , which are mostly covered by Cenozoic 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 . Some of this area has

3432-707: The Pacific. In addition to gold and silver and their related deposits, tin , iron , and 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 hydrothermal deposits To

3520-483: 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 fish compete with

3608-405: 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

Culiacán River - Misplaced Pages Continue

3696-449: The Sierra Madre from the central Mexican Plateau . The more southern one is the north–south Aguascalientes fault extending 150 kilometres (93 mi) 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

3784-600: The Southern Cordilleran Basaltic Andesite Suite. The tuffs 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 . During the Miocene, three periods of volcanism marked separate events in the Sierras. Each period

3872-403: The activity of magmatism 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 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

3960-490: The animal may have been extirpated; the black bear population is small, and the Mexican grizzly bear that once resided here is confirmed extinct. Jaguars and ocelots are also now rare. On the other hand, 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

4048-539: The area and surroundings. The Tarahumara frog lives in the oak and pine stands preferring moving water to pools. The southern extent of the 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 migratory path and others as native species . The migratory birds often use

4136-450: The area have deposited ore veins that are commercially viable. The landscape was shaped after rock placement. Rivers cut 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. The basement is thought to be Older North American basement, especially in

4224-442: 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 tropical species to use the mountain valleys for migration. Bird species endemic to

4312-421: 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

4400-422: 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

4488-400: 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. The mountains are often a corridor for species allowing more diversity in

SECTION 50

#1733085732246

4576-629: 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 13–18 °C (55–65 °F) above 1,800 metres (6,000 ft). Below-freezing temperatures can occur in

4664-577: The canyon of the Santiago River. Near these sediments late Oligocene to early Miocene granite and granodiorite intrusive bodies occur. A possible cause of this is that these bodies were roof pendants which were uplifted by plutons . Mesozoic limestone also occurs in northern portion of the mountains, mostly from the Cretaceous. Towards the end of the Cretaceous , the Laramide orogeny increased

4752-626: The early flows. Fissure-vein deposits have been divided into two groups of fissure 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 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 and replacement deposits along

4840-460: 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

4928-561: 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

5016-404: 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

5104-422: The formation of a soil crust , and soil acidification , which poses a risk to some grasslands as of 2002. 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

5192-483: The gulf, and the water is almost always warmer by the coast than the open ocean. For example, the waters surrounding La Paz reach 30 °C (86 °F) in August, while the waters in neighboring city Cabo San Lucas, only reach 26 °C (79 °F). Occasionally, the northern gulf will go through significantly cold winters. The water in the northern gulf can sometimes drop below 8 °C (46 °F), which can lead to

5280-609: The height of the mountain start around 3,040 m (9,970 ft) and go up to 3,300 m (10,800 ft). However, Cerro Barajas, at 26°24′N 106°5′W  /  26.400°N 106.083°W  / 26.400; -106.083 , may be as high as 3,300 m (10,800 ft) although other sources give 3,170 m (10,400 ft) as the elevation. Cerro Gordo, at 23°12′N 104°57′W  /  23.200°N 104.950°W  / 23.200; -104.950 , may have an elevation between 3,350 m (10,990 ft) and 3,340 m (10,960 ft). The southern end of

5368-420: The higher mountains, with 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 onshore flow is present. As the high pressure moves north, air is pulled off the Gulf of Mexico, bringing easterly winds aloft to

SECTION 60

#1733085732246

5456-465: The interior 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 depressions have formed in the southern Sierra Madre. The faulting decreases in the center of the range where the faults are mostly small normal faults , but increases once again on

5544-549: The middle, an arc of andesite was placed during the spreading of the Gulf of California . The basin and range-style faulting of the middle-late Miocene took place at the same time as the placement of alkali basalts , In the westernmost slopes mafic dikes formed. These events have also been linked to the subduction of the Farallon Plate . Episodes of volcanism continued into the Quaternary . The Sierras are believed to be

5632-523: The monsoon season. 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

5720-495: The mountains extending from Alaska down to these across western North America. 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 , larger and, in places, deeper than

5808-678: 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 , Sierra de Morones , Sierra Nochistlán, and Sierra Fría extending eastwards into Jalisco, Zacatecas, and Aguascalientes. The mountains act as

5896-417: 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

5984-620: The native population's opposition to these practices. 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 . The range runs parallel to the Pacific coast of Mexico, from just south of the Arizona-Sonora border southeast through eastern Sonora , western Chihuahua , Sinaloa , Durango , Zacatecas , Nayarit , Jalisco , Aguascalientes to Guanajuato , where it joins with

6072-527: The native species which has been a cause of concern among researchers, along with concerns about the effects of logging on these species. The Sonoran Desert is found in the northwestern foothills at 1,000–2,000 m (3,300–6,600 ft). 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

6160-524: The opening of the gulf, are found in the Bahía de Concepción, Baja California Sur. The gulf contains 37 major islands, the two largest being Isla Ángel de la Guarda and Isla Tiburón . Most of the islands are found on the west side of the gulf. In fact, many of the islands of the gulf are the result of volcanic eruptions that occurred during the early history of Baja California. The islands of Islas Marías , Islas San Francisco, and Isla Partida are thought to be

6248-401: 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 1,000 m (3,300 ft). 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

6336-514: The range contains none of the volcanism that is apparent in the northern range. These formations ended in the Paleocene . Eocene volcanism formed a series of andesitic and rhyolitic formations in the area, with spatial and temporal variations throughout. Most of the gold and silver 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

6424-522: 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 −22 °C (−8 °F) in the south of the range, and −24 and −26 °C (−11 and −15 °F) in the north in May. In June, dew points begin to increase from the May levels up to −20 °C (−4 °F) in the north and −16 °C (3 °F) in the south. By July these dew points are at −14 °C (7 °F) throughout

6512-424: 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 endemic species, and for allowing some species to extend their range . The dominant plants vary across the range, and the habitat that they present varies from scattered woodland to both deciduous and coniferous forest. The elevation and latitude in

6600-442: 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, 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 grasslands on some mountain tops, surrounded by the forest that occur in those areas. Plants in

6688-405: The range. The range allows higher dew points throughout these periods than the surrounding low lands. This rise in humidity accompanies the monsoon. 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 1,500–3,000 m (4,900–9,800 ft) throughout

6776-427: The result of such eruptions. The formations of the islands, however, are not dependent on each other. They were each formed as a result of an individual structural occurrence. Several islands, including Isla Coronados , are home to volcanoes. The Colorado River Delta contains several islands, such as Isla Montague . The gulf has more than 900 islets and islands which together total about 420 hectares. All of them as

6864-415: The rock that is most visible to be ignimbrites with lava flow layers. The region has a general strike from just west of north to just south of east. 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

6952-435: The second series of high magmatism formations. The Mid-Tertiary ignimbrite flare-up 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 calderas identified in the province. Three of these calderas are in Copper Canyon. The lava has formed a series of mafic rocks that comprise

7040-416: The shore for a habitat to be stable. Additionally, the color of the rocks can affect the organisms living on a shore. For example, darker rocks will be significantly warmer than lighter ones, and can deter animals that do not have a high tolerance for heat. The northern gulf experiences tidal ranges of up to 5 m (16 ft). Mixed semidiurnal tides are the norm throughout most of the Gulf. There are

7128-465: 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 , due to increased rainfall. Acidic soils may have lower calcium content, leading to lower plant soil quality . Soils along

7216-527: The specific types of animals found there. ) Geologic evidence is widely interpreted by geologists as indicating the gulf came into being around 5.3 million years ago as tectonic forces rifted the Baja California peninsula off the North American Plate . As part of this process, the East Pacific Rise propagated up the middle of the Gulf along the seabed. This extension of the East Pacific Rise

7304-583: 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,

7392-439: The types of rocks that make up a shore. Beaches with softer, more porous rocks (such as coquina limestone, rhyolites , granite , or diorite ) generally have a higher species richness than those with harder, smoother rocks (such as basalt or diabase ). Porous rocks will naturally have more cracks and crevices in them, making them ideal living spaces for many animals. The rocks themselves, however, generally need to be stable on

7480-534: The vast expanse covered by this federal protected area, conservation and management is carried out through a system of four regional directorates (one per state bordering the Gulf of California). The work of direct and indirect conservation done in the islands is governed by a single management program, published in 2000, which is complemented by local and specific management programs. The Directorate of Protection Area Wildlife California Gulf Islands in Baja California

7568-531: The west and southwest. These lower elevations are usually graded into by a stand of 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 savanna . Gulf of California The Gulf of California ( Spanish : Golfo de California ), also known as

7656-602: 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 reconstructions of the opening of the Gulf of California, as of 2003. On

7744-410: 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 erupt from the surface, and so there may be some association between the ignimbrite occurrence and faults; this can be used to find out information about different kinds of basement rock present. There are two faults dividing

#245754