The Navajo Section is a physiographic section of the larger

Colorado Plateau The Colorado Plateau is a physiographic and desert region of the Intermontane Plateaus, roughly centered on the Four Corners region of the Southwestern United States. This plateau covers an area of 336,700 km2 (130,000 mi2) within w ...

s Province, which in turn is part of the larger

Intermontane Plateaus In the context of physical geography, the Intermontane Plateaus is one of eight physiographic regions of the contiguous United States. The region consists mostly of plateaus and mountain ranges lying between the Rocky Mountains on the east and ...

physiographic Division.

Geography

The Navajo Section is located in northeastern

Arizona Arizona is a U.S. state, state in the Southwestern United States, Southwestern region of the United States, sharing the Four Corners region of the western United States with Colorado, New Mexico, and Utah. It also borders Nevada to the nort ...

and northwestern

New Mexico New Mexico is a state in the Southwestern United States, Southwestern region of the United States. It is one of the Mountain States of the southern Rocky Mountains, sharing the Four Corners region with Utah, Colorado, and Arizona. It also ...

. It is named for the

Navajo Nation The Navajo Nation (), also known as Navajoland, is an Indian reservation of Navajo people in the United States. It occupies portions of northeastern Arizona, northwestern New Mexico, and southeastern Utah. The seat of government is located in ...

, with about half of the area of the section on the Navajo Reservation. The section is characterized by broad rolling plains on easily eroded and carved rocks, with

cuesta A cuesta () is a hill or ridge with a gentle slope on one side, and a steep slope on the other. In geology, the term is more specifically applied to a ridge where a harder sedimentary rock overlies a softer layer, the whole being tilted somew ...

s (ridges) and tablelands capped by gently dipping resistant

sandstone Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...

beds. One of the most prominent landform features of the Navajo Section is

Shiprock Shiprock (, "rock with wings" or "winged rock") is a monadnock rising nearly above the high-desert plain of the Navajo Nation in San Juan County, New Mexico, United States. Its peak elevation is above sea level. It is southwest of the town ...

, a

monadnock An inselberg or monadnock ( ) is an isolated rock hill, knob, ridge, or small mountain that rises abruptly from a gently sloping or virtually level surrounding plain. In Southern Africa, a similar formation of granite is known as a koppie, an ...

formation near the town of Shiprock, New Mexico.

Elevations

The lowest point in the Navajo Section is about , near the

Four Corners Four Corners is a region of the Southwestern United States consisting of the southwestern corner of Colorado, southeastern corner of Utah, northeastern corner of Arizona, and northwestern corner of New Mexico. Most of the Four Corners regio ...

area. The boundary between this section and the Canyon Lands Section is nearby, in the San Juan River basin. The highest point of the Navajo Section is at Chromo Mountain on the

Continental Divide A continental divide is a drainage divide on a continent such that the drainage basin on one side of the divide feeds into one ocean or sea, and the basin on the other side either feeds into a different ocean or sea, or else is endorheic, not ...

near Chama, New Mexico.

Adjacent

Adjacent to the Navajo Section are the: # Canyon Lands Section to the north. #

Rio Grande rift The Rio Grande rift is a north-trending continental rift zone. It separates the Colorado Plateau in the west from the interior of the North American craton on the east. The rift extends from central Colorado in the north to the state of Chihuah ...

of the

Basin and Range Province The Basin and Range Province is a vast United States physiographic region, physiographic region covering much of the inland Western United States and Northern Mexico, northwestern Mexico. It is defined by unique basin and range topography, charac ...

to the east. # Acoma-Zuni Section to the south. # Grand Canyon Section to the west

Geology and physiography

The area is predominantly generally horizontal

beds with some

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of Clay mineral, clay minerals (hydrous aluminium phyllosilicates, e.g., Kaolinite, kaolin, aluminium, Al2Silicon, Si2Oxygen, O5(hydroxide, OH)4) and tiny f ...

sequences of late

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...

and early

Cenozoic The Cenozoic Era ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterized by the dominance of mammals, insects, birds and angiosperms (flowering plants). It is the latest of three g ...

age. A few areas of the section also have abundant volcanic necks and

buttes In geomorphology, a butte ( ) is an isolated hill with steep, often vertical sides and a small, relatively flat top; buttes are smaller landforms than mesas, plateaus, and tablelands. The word ''butte'' comes from the French word , meaning 'k ...

, but due to the arid weather and soft sandstone, many of the rock formations of the area have eroded to form distinctive features of long

s, shallow canyons and valleys, narrow fan terraces, undulating plateaus, isolated

mesas A mesa is an isolated, flat-topped elevation, ridge, or hill, bounded from all sides by steep escarpments and standing distinctly above a surrounding plain. Mesas consist of flat-lying soft sedimentary rocks, such as shales, capped by a r ...

, steep hills, and some shale

badlands Badlands are a type of dry terrain where softer sedimentary rocks and clay-rich soils have been extensively eroded."Badlands" in '' Chambers's Encyclopædia''. London: George Newnes, 1961, Vol. 2, p. 47. They are characterized by steep slopes, ...

. ;San Juan Basin Near the Four Corners area is a steeply tilted

monocline A monocline (or, rarely, a monoform) is a step-like fold in rock strata consisting of a zone of steeper dip within an otherwise horizontal or gently dipping sequence. Formation Monoclines may be formed in several different ways (see diagram) ...

known as The Hogback, which trends southwestward from where the San Juan River enters the area. Here the San Juan River flows into an area known as the

San Juan Basin The San Juan Basin is a geologic structural basin located near the Four Corners region of the Southwestern United States. The basin covers 7,500 square miles and resides in northwestern New Mexico, southwestern Colorado, and parts of Utah a ...

, where the western San Juan Basin is typified by exposures of the Fruitland and Menefee Formations. A stepped sequence of high stream terraces, present above the San Juan River and its tributaries, represents abandoned

Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...

flood plains.

References

External links