The San Bernardino Valley of Arizona is a northeast-by-southwest trending valley in extreme southeast

Cochise County Cochise County () is a county in the southeastern corner of the U.S. state of Arizona. It is named after the Native American chief Cochise. The population was 125,447 at the 2020 census. The county seat is Bisbee and the most populous city is ...

, Arizona. The north end of the valley merges into the northwest-by-southeast trending

San Simon Valley The San Simon Valley is a broad valley east of the Chiricahua Mountains, in the northeast corner of Cochise County, Arizona and southeastern Graham County, Arizona, Graham County, with a small portion near Antelope Pass in Hidalgo County, New Mex ...

; both merge in western perimeter Hidaldgo County, New Mexico. The valley is an asymmetric

graben In geology, a graben () is a depressed block of the crust of a planet or moon, bordered by parallel normal faults. Etymology ''Graben'' is a loan word from German, meaning 'ditch' or 'trench'. The word was first used in the geologic contex ...

. Valleys border all flanks of the Chiricahua Mountains

massif In geology, a massif ( or ) is a section of a planet's crust that is demarcated by faults or flexures. In the movement of the crust, a massif tends to retain its internal structure while being displaced as a whole. The term also refers to a ...

(and some attached sub-ranges); The San Bernardino Valley borders the southeast of the

Chiricahua Mountains The Chiricahua Mountains massif is a large mountain range in southeastern Arizona which is part of the Basin and Range province of the west and southwestern United States and northwest Mexico; the range is part of the Coronado National Forest. ...

; the San Simon Valley borders the northeast. San Bernardino Valley abuts the Peloncillo Mountains of

New Mexico ) , population_demonym = New Mexican ( es, Neomexicano, Neomejicano, Nuevo Mexicano) , seat = Santa Fe , LargestCity = Albuquerque , LargestMetro = Tiguex , OfficialLang = None , Languages = English, Spanish ( New Mexican), Navajo, Ker ...

on the east, and the smaller adjoining range to its south, the

Guadalupe Mountains The Guadalupe Mountains ( es, Sierra de Guadalupe) are a mountain range located in West Texas and southeastern New Mexico. The range includes the highest summit in Texas, Guadalupe Peak, , and the "signature peak" of West Texas, El Capitan, both ...

. To the south, the valley borders

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 ...

Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...

and the north regions of the

Sierra del Tigre Sierra del Tigre is a mountain range in northeastern Sonora, Mexico at the northern region of the Sierra Madre Occidental. The region contains sky island mountain ranges, called the Madrean Sky Islands, some separated from the Sierra Madre Occid ...

range, of Mexico. At the northern end of the Sierra del Tigre, the Rio San Bernardino joins the

Bavispe River The Rio Bavispe or Bavispe River is a river in Mexico which flows briefly north then mainly south by southwest until it joins with the Aros River to become the Yaqui River, eventually joining the Gulf of California. History Historically, the Rio ...

, then heads south to Mexico. To the northwest and west, the San Bernardino Valley abuts the Chiricahuas, Pedregosa, and Perilla Mountains. At the very south of the valley, north of

Douglas, Arizona Douglas is a city in Cochise County, Arizona, United States that lies in the north-west to south-east running Sulpher Springs Valley. Douglas has a border crossing with Mexico at Agua Prieta and a history of mining. The population was 16,531 in ...

–

Agua Prieta Agua Prieta (English: ''Dark Water'', Opata: ''Bachicuy'') is a town in Agua Prieta Municipality in the northeastern corner of the Mexican state of Sonora. It stands on the Mexico–U.S. border, adjacent to the town of Douglas, Arizona. The mun ...

, Mexico lies the

San Bernardino National Wildlife Refuge The San Bernardino National Wildlife Refuge is located on the U.S.-Mexico border in Cochise County, Arizona. Situated at elevation in the bottom of a wide valley, the refuge encompasses a portion of the headwaters of the Yaqui River, which dra ...

. The refuge, grasslands, and wetlands are part of the south and southwest-flowing

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 ...

of Mexico that reaches the northeast region 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 ...

Geronimo–San Bernardino volcanic field

The San Bernardino Valley floor is covered by

basalt Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial ...

lava 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 ...

dating from 0.27 to 1.0 Ma (million years ago). The Geronimo–San Bernardino volcanic field is part of the larger

Boot Heel volcanic field The Boot Heel volcanic field is located in the Bootheel region of southwest New Mexico, adjacent areas of southeastern Arizona, and northwest Mexico. The field covers an area of more than 24,000 km2.Baldridge, W. Scott, ''Geology of the Ame ...

. The field covers some 850 km² and consists of

olivine 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 ...

flows,

tuff ring Phreatomagmatic eruptions are volcanic eruptions resulting from interaction between magma and water. They differ from exclusively magmatic eruptions and phreatic eruptions. Unlike phreatic eruptions, the products of phreatomagmatic eruptions cont ...

s and

maar A maar is a broad, low-relief volcanic crater caused by a phreatomagmatic eruption (an explosion which occurs when groundwater comes into contact with hot lava or magma). A maar characteristically fills with water to form a relatively shallow ...

s with 130 identified

volcanic vent A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plates are ...

areas and

cinder cone A cinder cone (or scoria cone) is a steep conical hill of loose pyroclastic fragments, such as volcanic clinkers, volcanic ash, or scoria that has been built around a volcanic vent. The pyroclastic fragments are formed by explosive eruptions o ...

s.Evans, Stanley H. and W. P. Nash, ''Petrogenesis of xenolith-bearing basalts from southeastern Arizona,'' American Mineralogist, Volume 64, pp. 249–267, 1979
/ref>

References

External links

*

* ttp://www.cuencalosojos.org/ Cuenca Los Ojos Foundation
Paramore Crater (coordinates), (Topoquest)
Valleys of Arizona Chiricahua Mountains Landforms of Cochise County, Arizona Landforms of Hidalgo County, New Mexico Volcanic fields of New Mexico Volcanism of Mexico