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Location of Arizona in the United States.
The South Rim of the Grand Canyon.

Arizona is a landlocked state situated in the southwestern region of the United States of America. Arizona shares land borders with Utah to the north, the Mexican state of Sonora the south, New Mexico to the east, and Nevada to the west. Arizona shares water borders with California and the Mexican state of Baja California to the west along the Colorado River. Arizona is also one of the Four Corners states, at which Arizona touches Colorado.

Arizona has an area of 113,998 square miles (295,253 km2) square miles, making it the sixth largest U.S. state.[1] Of Arizona's total area, 0.32% consists of water, which makes Arizona the state with the second lowest percentage of water area (New Mexico is the lowest at 0.19%).[1] Arizona spans about 335 miles (539 km) at its widest, and 390 miles (628 km) miles at its longest, and has an average elevation of about 4,000 feet (1,200 m).[2] The geographic center of Arizona is located in Yavapai County, 55 miles (89 km) east-southeast of Prescott.


Political geography

Map of Arizona with its counties outlined.

Arizona is divided into 15 counties, and has 90 incorporated cities and towns. Approximately 65 percent of Arizona residents live in Maricopa County, which had a population of 3,880,181 as of the 2000 Census. Maricopa County ranks fourth among the nation's counties in terms of population, and is more populated than 24 of the U.S. states. The county seat of Maricopa County is Phoenix, which is Arizona's largest city and capital. The next most populous county is Pima County, which had a 2000 population of 843,746. The county seat of Pima County is Tucson, where nearly all of the population is concentrated. Combined, appromixately 80 percent of Arizona residents live in either Maricopa County or Pima County, even though the two counties make up 16% of Arizona's total area. Because of the high population of Maricopa County and Pima County, both counties are dominant in state politics.

Approximately 15% of Arizona is privately owned, the remaining land consisting primarily of public forest and park land, Native American reservations, military institutions, and swaths of wilderness held by the Bureau of Land Management. Arizona is home to 21 federally recognized tribes, which are each semi-autonomous. The large majority are part of the Navajo Nation, which is the largest Native American reservation in terms of population and size. The Navajo Reservation covers all of northeastern Arizona along with portions of New Mexico and Utah, and had a population of 180,462 as of the 2000 census.


Due to the state's large area and range of elevation, there is a variety of localized climate conditions. Overall, most of Arizona receives little precipitation, and is classified as having either an arid or semi-arid climate. The northern parts of the state and the mountainous areas tend to have cooler climates, while the southern parts of the state tend to be warm year round.

Average precipitation of Arizona.


Precipitation in Arizona is governed by elevation and the season of year. the peak periods of rainfall are during the early winter, when storm systems from the Pacific Ocean cross the state, and during the summer, when moisture-bearing winds sweep into Arizona from the southeast, which obtain moisture from the Gulf of Mexico. Summer rains tend to occur in the form of thunderstorms, which result from excessive heating of the ground and the lifting of moisture-laden air along mountain ranges. These thunderstorms can cause strong winds, brief periods of blowing dust, and infrequently cause hail. The heaviest precipitation is found in the mountain ranges of central and southeastern Arizona, while the driest conditions are found in the arid regions of southwestern Arizona.

The amount of days with measurable precipitation can vary from around 70 in the Flagstaff area to 15 in the Yuma area.[3] The highest elevations of Arizona receive between 25 and 30 inches (63 to 76 cm) of precipitation annually, and the lower elevations receive between 7 and 20 inches (18 to 51 cm). The driest part of the state is the southwestern region, which receives under 3 inches (8 cm) of rain a year.[4] Annual average humidity values vary from 55% in Flagstaff to 33% in Yuma. Due to the high temperatures, low humidity, and occurrence of sunshine, Arizona has high rates of evaporation. Average annual lake evaporation varies from about 80 inches (200 cm) inches in the southwestern part of the state to about 50 inches (130 cm) in the northeast.[5]


While the desert parts of Arizona are renowned for their warm climates, snow is not uncommon to portions of Arizona. From November through March, when storm systems from the Pacific Ocean cross the state, heavy snow can accumulate in the mountains of central and northern Arizona. Moderate snow can occur as far south as Nogales, Arizona, which is located on the southern border with Mexico, since it experiences below-freezing nighttime temperatures during the winter.

The rims of the Grand Canyon experience snow during the winter due to their high altitudes. The South Rim of the Grand Canyon, located at an altitude averaging 7000 feet (2134 m), receives 60 inches (132 cm) of snow annually, and the North Rim of the Grand Canyon, located at an altitude over 8000 feet (2438 m) receives 144 inches (317 cm) of snow.[6]


Because of the dry climate and sparse cloud cover throughout the state, temperatures can vary dramatically, from day to night, and from season to season. Parts of Arizona located in the Sonoran Desert have warm daytime temperatures year round, while other parts of the state experience seasonal coldness regularly. The average daily temperatures of Yuma, which is located near Arizona's southwestern corner, range from 43° to 67°F (6° to 19°C) in January, and from 81° to 106°F (27° to 41°C) in July. In Flagstaff, located in the state's central interior, the average daily temperatures range from 14° to 41°F (–10° to 5°C) during January, and from 50° to 81°F (10° to 27°C) in July.[4] The record high temperature for Arizona was 128°F (53°C), measured in Lake Havasu City on June 29, 1994. The record low temperature for Arizona was -40°F (-40°C), measured at Hawley Lake on January 7, 1971.[7]

Monthly Normal High and Low Temperatures (°F) For Various Arizona Cities
City Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Phoenix[8] 67/45 71/48 76/51 85/58 94/67 104/75 107/81 105/80 99/75 88/63 75/50 70/44
Tucson[9] 66/42 70/45 75/49 82/54 91/63 100/72 101/77 99/75 95/71 85/60 74/48 66/42
Yuma[10] 70/46 75/49 80/53 87/58 95/65 104/73 107/81 106/81 101/75 90/64 77/52 69/46
Flagstaff[11] 43/16 46/19 50/23 58/27 68/34 79/41 82/50 80/49 74/42 63/31 51/22 44/17
Prescott[12] 51/23 54/26 58/30 65/35 74/43 85/51 88/58 86/57 81/50 71/39 60/29 52/23
Lake Havasu City[13] 65/43 71/47 76/52 85/59 93/68 103/77 108/83 106/81 100/75 88/63 74/50 65/43
Sierra Vista[14] 62/34 65/36 70/41 77/46 85/53 93/62 93/66 90/64 87/60 79/50 69/40 62/34
Show Low[15] 47/23 52/26 58/31 66/37 74/45 85/53 87/59 84/58 79/51 69/40 56/30 48/23
Page[16] 43/26 50/30 59/37 69/44 78/53 90/62 95/68 92/66 84/58 70/47 54/35 44/27

Physiographic regions

Map of the physiographic regions of Arizona.
Shaded relief map of Arizona.

Arizona can be divided into two major physiographic regions: the Colorado Plateau and the Basin and Range Province, and one intermittent zone between the two called the Transition Zone.

Colorado Plateau

The Colorado Plateau is a semi-arid, mostly flat-lying region ranging from 5,000 to 8,000 feet (1524 m to 2438 m) in elevation,[2] centered on the Four Corners region. The Colorado Plateau encompasses an area of approximately 140,000 square miles (360,000 km2).[17] It consists of northern Arizona, except for a small portion of northwestern Arizona. The Plateau ends with the step rock wall of the Mogollon Rim, which defines the southern edge of the plateau. The Colorado Plateau has the nickname "Red Rock Country" because of its brightly colored sedimentary rock left visible by dryness and erosion, and protected from deformation. The geology of the Colorado Plateau is exhibited by the canyons of the Colorado River, and the Grand Canyon exposes one of the most unique rock sequences in the world. The area hosts many distinctive natural features unique to Arizona, including the Grand Canyon, Antelope Canyon, Meteor Crater, Painted Desert, and the Petrified Forest.

Transition Zone

The Transition Zone is a northwest-trending escarpment of mountainous terrain in central Arizona shaped by the intersection of the higher-level Colorado Plateau with the lower-level Basin and Range Province. The area is termed the Transition Zone because it is transitional between the two regions, with characteristics from both. The area consists of a series of rugged mountain ranges and valleys. Many of the mountains of the Transition Zone are part of the Mogollon Rim, a cliff which extends 115 miles (190 km) from northern Yavapai County eastward to near the border with New Mexico.[18] The mountain ranges of the Transition Zone include the Mazatzal, Santa Maria, Sierra Ancha, and White mountain ranges. Because of the range of elevation within the Transition Zone, climatic conditions can vary widely over small areas. The Transition Zone tends to be one of the areas of Arizona to receive heavier rainfall due to its mountainous terrain, and experiences a variation in temperature by altitude.

Basin and Range Province

The Basin and Range Province is a region occupying the southern part of Arizona, along with a strip of land consisting of the western part of the state. It is also part of a much larger region encompassing southwestern New Mexico, western Utah, and virtually all of Nevada, and extending into northwestern Mexico. The Basin and Range is characterized by steep, linear mountain ranges alternating with lengthy deserts. The mountain ranges, which poke through the lengthy desert plains surrounding them, can rise above 9,000 feet (2,700 m), and create biological islands inhabited by cool-climate plants and animals.[2] The geology of the Basin and Range is the result of crustal extension of the North American plate. Due to the crustal extension, the area of the crust underneath the region is some of the thinnest in the world. The Basin and Range supplies nearly all of the copper mined in Arizona, and contains other minerals such as gold, silver, and barite.


The major rivers of Arizona are the Colorado River, and one of its main tributaries, the Gila River. Nearly all of Arizona is drained by either the Colorado River or one of its tributaries.

Colorado River

The Colorado River is vital to Arizona because of the perennial dryness of the region. The river is famous because of its role in the creation of the Grand Canyon, which was created over a period of six million years. Several irrigation systems divert water from the Colorado River, of which the one most vital to Arizona is the Central Arizona Project. The Central Arizona Project, which is 336 miles (541 km) long, diverts 1.5 million acre-feet (1.85 km3) of water from Lake Havasu City into central and southern Arizona.[19] The river is also utilized for hydroelectric power through various dams along the river. The dams on the Colorado River, going downstream, are the Glen Canyon Dam, Hoover Dam, Davis Dam, Parker Dam, Imperial Dam, Laguna Dam, and the Morelos Dam.

Gila River

The Gila River is 650 miles (1,050 km) long, and extends from southwestern New Mexico to its confluence with the Colorado River near Yuma. While the upper Gila River is free-flowing, the portion of the river below the Phoenix area is usually either a trickle of completely dry because of the diversion of water for irrigation. The only major dam on the Gila River is Coolidge Dam, located 31 miles (50 km) southeast of Globe, Arizona.


Sonoran Desert 35 miles (56 km) west of Maricopa, Arizona

Sonoran Desert

The Sonoran Desert covers the southwestern area of Arizona, including the cities of Phoenix, Tucson, and Yuma. The Sonoran Desert is bounded on the north by the The Sonoran Desert is one of the hottest deserts of the United States, and maintains warm temperatures year round. Despite the sparse amounts of precipitation during the year, the desert is home to a diverse population of flora and fauna because it has two rainy seasons a year. Several plant populations thrive because of their specialized adaptions to the climate, and various species of cactus can be found in the wild. The Sonoran Desert is the only place in the world where the saguaro cactus grows in the wild, and the fishhook, prickly pear, and organ pipe are among other types of cactus found in the Sonoran Desert.

Mojave Desert

Northwestern Arizona contains part of the Mojave Desert, which is at a higher altitude than the Sonoran Desert. The boundaries of the Mojave Desert can be determined by the presence of Yucca brevifolia (Yucca palm), which is endemic to the desert. Unlike the Sonoran Desert, the Mojave Desert has few trees, both in number and diversity.

Painted Desert

The Painted Desert is a broad area of badlands located on the Colorado Plateau in Northern Arizona. It covers at least 146 square miles (380 km2) acres, and stretches from 30 miles (48 km) north of Cameron, near the Grand Canyon, ending just beyond the Petrified Forest.[20] The Painted Desert derives its name from the multitude of colored sediments and bentonite clay seen from its Chinle rock formation, left exposed by erosion. In the southern portion of the desert the remains of a Triassic Era coniferous forest have fossilized over millions of years. Most of the Painted Desert is located within the Najavo Nation, and is only accessible by foot.

Chihuahuan Desert

A small portion of southeastern Arizona is part of the Chihuahuan Desert. Because of its higher elevation in comparison to the Sonoran Desert, it tends to have milder temperatures during the summer.


  1. ^ a b Summary of 2000 Census Table 17
  2. ^ a b c Weir, Bill. The Land,
  3. ^ Arizona Weather & When to Go,
  4. ^ a b Arizona - Climate
  5. ^ CLIMATE OF ARIZONA, Desert Research Institute Western Regional Climate Center.
  6. ^ Grand Canyon National Park Weather, Grand Canyon National Park.
  7. ^ U.S. Extreme Record Temperatures & Differences, Golden Gate Weather Services.
  8. ^ Phoenix, Arizona, Weather Channel.
  9. ^ Tucson, Arizona, Weather Channel.
  10. ^ Yuma, Arizona, Weather Channel.
  11. ^ Flagstaff, Arizona, Weather Channel.
  12. ^ Prescott, Arizona, Weather Channel.
  13. ^ Lake Havasu City, Arizona, Weather Channel.
  14. ^ Sierra Vista, Arizona, Weather Channel.
  15. ^ Show Low, Arizona, Weather Channel.
  16. ^ Page, Arizona, Weather Channel.
  17. ^ Geology of the Colorado Plateau, National Park Service.
  18. ^ Mogollon Rim, USGS GNIS.
  19. ^ Central Arizona Project
  20. ^ Painted Desert Arizona, Arizona Leisure.

External links


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