Editing Southwestern United States (section)

==Regional geography==
[[File:ISS View of the Southwestern USA.JPG|thumb|Panoramic view of the southwestern United States]]
The geography of the region is mainly made up of four features: the [[Mojave Desert|Mojave]], [[Sonoran Desert|Sonoran]], and [[Chihuahuan Desert]]s, and the [[Colorado Plateau]]; although there are other geographical features as well, such as a portion of the [[Great Basin Desert]]. The deserts dominate the southern and western reaches of the area, while the plateau (which is largely made up of high desert) is the main feature north of the [[Mogollon Rim]].<ref name=ASW1>{{cite web | url=http://www.americansouthwest.net/deserts.html | publisher=The American Southwest | title=Deserts of Southwest USA | access-date=July 6, 2015}}</ref> The two major rivers of the region are the [[Colorado River]], running in the northern and western areas, and the [[Rio Grande]], running in the east, north to south.
[[File:Chihuahuan Desert from South Rim BIBE.jpg|left|thumb|The Chihuahuan desert terrain mainly consists of [[Drainage basin|basins]] broken by numerous small [[mountain range]]s.]]
Formed approximately 8000 years ago, the Chihuahuan Desert is a relatively dry desert,<ref name=NMSU /> although it is slightly wetter than the Sonoran Desert to the west.<ref name=ASW1 /> The Chihuahuan Desert spreads across the southeastern portion of the region, covering from southeastern Arizona, across southern and central New Mexico, and the portion of western Texas included in the Southwest.<ref name=NMSU>{{cite web | url=http://ddl.nmsu.edu/chihuahua.html | publisher=New Mexico State University | title=The Chihuahuan Desert | access-date=July 6, 2015 | url-status=dead | archive-url=https://web.archive.org/web/20121227092714/http://ddl.nmsu.edu/chihuahua.html | archive-date=December 27, 2012 | df=mdy-all }}</ref> While it is the second largest desert in the United States,<ref name=ASW1 /> only a third of the desert is within the United States, with the rest in Mexico.<ref name=NPSCD /> El Paso and Albuquerque are the major US cities in this desert, with other smaller cities being [[Las Cruces, New Mexico|Las Cruces]] and [[Roswell, New Mexico|Roswell]] in New Mexico and [[Willcox, Arizona|Willcox]] in Arizona.<ref name=ASW1 />

The elevation in the Chihuahuan Desert varies from about {{convert|1,750|to|6,000|ft|m|abbr=off|sp=us|-2}}, as well as several larger mountain ranges within or bordering this desert including the [[Black Range]], [[Organ Mountains]], [[Capitan Mountains]], [[Manzano Mountains]], [[Sacramento Mountains (New Mexico)|Sacramento Mountains]], [[Sandia Mountains]], [[Magdalena Mountains]], and [[Chiracahua Mountains]], plus many smaller mountain ranges contained in the area, namely the [[Animas Mountains|Animas]], [[San Andres Mountains|San Andres]], [[Guadalupe Mountains]], and [[Doña Ana Mountains]] in New Mexico; and the [[Franklin Mountains (Texas)|Franklin]], [[Hueco Mountains|Hueco]], and [[Davis Mountains]] in Texas. It also reaches up into the foothills of the higher ranges such as the [[Black Range]] and [[Oscura Mountains]] in New Mexico. High above the desert, these forest-covered and sometimes snow-capped mountains form [[sky island]]s, with radically different flora and fauna than the surrounding desert below. The sky islands also supply the surrounding desert foothills with flowing water during the spring runoff and after the summer storms of the [[New Mexican Monsoon|New Mexican monsoon season]]. The Chihuahuan is a "rain shadow" desert, formed between two mountain ranges (the Sierra Madre Occidental on the west and the Sierra Madre Oriental on the east) which block oceanic precipitation from reaching the area.<ref name=NMSU /> The Chihuahuan Desert is considered the "most biologically diverse desert in the Western Hemisphere and one of the most diverse in the world," and includes more species of cacti than any other desert in the world.<ref name=NPSCD>{{cite web | url=http://www.nps.gov/cave/learn/nature/deserts.htm | publisher=National Park Service | title=Chihuahuan Desert | access-date=July 6, 2015}}</ref> The most prolific plants in this region are [[agave]], [[yucca]] and [[creosote bush]]es,<ref name=ASW1 /> in addition to the ubiquitous presence of various cacti species.

[[File:AguaFriaNM (cropped).jpeg|thumb|upright|Saguaro cactus in the Sonoran Desert.]]
When people think of the desert southwest, the landscape of the Sonoran Desert is what mostly comes to mind.<ref name=ASW1/> The Sonoran Desert makes up the southwestern portion of the Southwest; most of the desert lies in Mexico, but its United States component lies on the southeastern border of California, and the western 2/3 of southern Arizona. Rainfall averages between {{convert|4|and|12|in|mm|abbr=on}} per year, and the desert's most widely known inhabitant is the [[saguaro cactus]], which is unique to the desert.<ref name=WWF>{{cite web | url=http://www.worldwildlife.org/ecoregions/na1310 | publisher=World Wildlife Fund | title=Southern North America: Southwestern United States into northwestern Mexico | access-date=July 6, 2015}}</ref><ref name=LP>{{cite web | url=http://www.questconnect.org/sw_american_southwest.htm | publisher=Lonely Planet | title=The American Southwest; Footsteps of the Ancients Expedition | date= October 1, 2001 | last=Green | first=Kim & Don | access-date=July 6, 2015}}</ref> It is bounded on the northwest by the Mojave Desert, to the north by the Colorado Plateau and to the east by the [[Arizona Mountains forests]] and the Chihuahuan Desert.<ref>{{cite web | url=http://www.desertmuseum.org/books/nhsd_geologic_origin.php | publisher=Arizona-Sonora Desert Museum | title=The Geologic Origin of the Sonoran Desert | access-date=July 6, 2015}}</ref> Aside from the trademark saguaro, the desert has the most diverse plant life of any desert in the world,<ref name=WWF /> and includes many other species of cacti, including the organ-pipe, senita, prickly pear, barrel, fishhook, hedgehog, cholla, silver dollar, and jojoba.<ref name=WWF /><ref name=LP /> The portion of the Sonora Desert which lies in the Southwestern United States is the most populated area within the region. Six of the top ten major population centers of the region are found within its borders: Phoenix, [[Tucson, Arizona|Tucson]], [[Mesa, Arizona|Mesa]], [[Chandler, Arizona|Chandler]], [[Glendale, Arizona|Glendale]], and [[Scottsdale, Arizona|Scottsdale]], all in Arizona. Also within its borders are [[Yuma, Arizona|Yuma]] and [[Prescott, Arizona]].<ref name=ASW1 />

The most northwest portion of the American Southwest is covered by the Mojave Desert. Bordered on the south by the Sonoran Desert and the east by the Colorado Plateau, its range within the region makes up the southeast tip of Nevada, the southwestern corner of Utah and the northwestern corner of Arizona.<ref name=LP /> In terms of topography, the Mojave is very similar to the Great Basin Desert, which lies just to its north.<ref name=ASW1/> Within the region, Las Vegas is the most populous city; other significant population centers include [[Laughlin, Nevada|Laughlin]] and [[Pahrump, Nevada|Pahrump]] in Nevada, [[St. George, Utah|St. George]] and [[Hurricane, Utah|Hurricane]] in Utah, and [[Lake Havasu City, Arizona|Lake Havasu City]], [[Kingman, Arizona|Kingman]], and [[Bullhead City, Arizona|Bullhead City]] in Arizona. The Mojave is the smallest, driest and hottest desert within the United States.<ref name=LP /> The Mojave gets less than {{convert|6|in|mm|abbr=on|-1}} of rain annually, and its elevation ranges from {{convert|3000|to|6000|ft|m|abbr=off|sp=us|-2}} above sea level.<ref name=DD1>{{cite web | url=http://mojavedesert.net/description.html | publisher=Digital-Desert | title=What & Where is the Mojave Desert? | access-date=July 6, 2015}}</ref> The most prolific vegetation is the tall [[Joshua tree]], which grow as tall as {{convert|40|ft|m|abbr=on}}, and are thought to live almost 1000 years.<ref name=LP /> Other major vegetation includes the Parry saltbush and the Mojave sage, both only found in the Mojave, as well as the creosote bush.<ref>{{cite web | url=http://www.nps.gov/jotr/learn/nature/mojave.htm | publisher=National Park Service | title=Mojave Desert | access-date=July 6, 2015}}</ref>

[[File:Delicate arch sunset.jpg|thumb|left|The Delicate Arch at [[Arches National Park]]]]
The [[Colorado Plateau]] varies from the large stands of forests in the west, including the largest stand of [[ponderosa pine]] trees in the world, to the Mesas to the east.<ref>{{cite web | url=http://www.ncsu.edu/project/wildfire/Arizona/prescott/prescott.html | publisher=North Carolina State University | title=Community Responses to Wildland Fire Threats in Arizona | access-date=July 2, 2015}}</ref> Although not called a desert, the Colorado Plateau is mostly made up of high desert. Within the Southwest U.S. region, the Colorado is bordered to the south by the Mogollon Rim and the Sonoran Desert, to the west by the Mojave Desert, and to the east by the [[Rocky Mountains]], the [[Rio Grande Rift]] valley, and the [[Llano Estacado]].<ref name=LP /> The Plateau is characterized by a series of plateaus and mesas, interspersed with canyons.<ref name=LP/> The most dramatic example is the [[Grand Canyon]].<ref>{{cite web | url=http://arizonaexperience.org/land/colorado-plateau | archive-url=https://web.archive.org/web/20130130090823/http://arizonaexperience.org/land/colorado-plateau | url-status=usurped | archive-date=January 30, 2013 | publisher=The Arizona Experience | title=Colorado Plateau | access-date=July 6, 2015}}</ref> But that is one of many dramatic vistas included within the Plateau, which includes spectacular lava formations, "painted" deserts, sand dunes, and badlands.<ref>{{cite web | url=http://www.cpluhna.nau.edu/Places/coloplateau4.htm | publisher=Northern Arizona University | title=The Colorado Plateau Region (page 4 of 4) | last=Wheeler | first=Ray | access-date=July 6, 2015 | archive-url=https://web.archive.org/web/20150516101657/http://www.cpluhna.nau.edu/Places/coloplateau4.htm | archive-date=May 16, 2015 | url-status=dead | df=mdy-all }}</ref> One of the most distinctive features of the Plateau is its longevity, having come into existence at least 500 million years ago.<ref>{{cite web | url=http://www.cpluhna.nau.edu/Places/places.htm | publisher=Northern Arizona University | title=The Colorado Plateau Region (page 1 of 4) | last=Wheeler | first=Ray | access-date=July 6, 2015 | archive-url=https://web.archive.org/web/20150429134451/http://cpluhna.nau.edu/Places/places.htm | archive-date=April 29, 2015 | url-status=dead | df=mdy-all }}</ref> The Plateau can be divided into six sections, three of which fall into the Southwest region. Beginning with the Navajo section forming the northern boundary of the Southwestern United States, which has shallower canyons than those in the Canyonlands section just to its north; the Navajo section is bordered to the south by the Grand Canyon section, which of course is dominated by the Grand Canyon; and the southeasternmost portion of the Plateau is the Datil section, consisting of valleys, mesas, and volcanic formations.<ref name=EBCP>{{cite web | url=http://www.britannica.com/place/Colorado-Plateau | publisher=Encyclopædia Britannica | title=Colorado Plateau | access-date=July 6, 2015}}</ref> Albuquerque is the most populous city often considered at the edge of this portion contained in the Southwest region, but Santa Fe, New Mexico and Flagstaff, Arizona, are also significant population centers.

[[File:Four Corners Monument (1).jpg|thumb|[[Four Corners Monument]]]]
[[Phoenix, Arizona|Phoenix]], Tucson, and [[Las Vegas]] dominate the westernmost metropolitan areas in the Southwest, while [[Albuquerque]]-[[Santa Fe, New Mexico|Santa Fe]] and [[El Paso, Texas|El Paso]]-[[Las Cruces, New Mexico|Las Cruces]] dominate the easternmost metropolitan areas.<ref>''Meinig'', pp. 123–136</ref>