In structural geology

Structural geology

Structural geology is the study of the three-dimensional distribution of rock units with respect to their deformational histories. The primary goal of structural geology is to use measurements of present-day rock geometries to uncover information about the history of deformation in the rocks, and...

, a uniclinal structure, homoclinal structure, unicline or homocline (from old  = same, cline = inclination) is a sedimentary rock

Sedimentary rock

Sedimentary rock are types of rock that are formed by the deposition of material at the Earth's surface and within bodies of water. Sedimentation is the collective name for processes that cause mineral and/or organic particles to settle and accumulate or minerals to precipitate from a solution....

 unit, which may also be associated with a stratigraphic landform

Landform

A landform or physical feature in the earth sciences and geology sub-fields, comprises a geomorphological unit, and is largely defined by its surface form and location in the landscape, as part of the terrain, and as such, is typically an element of topography...

, where the underlying strata

Stratum

In geology and related fields, a stratum is a layer of sedimentary rock or soil with internally consistent characteristics that distinguish it from other layers...

 are tilted in the same direction, especially with near uniform dip angle

Strike and dip

Strike and dip refer to the orientation or attitude of a geologic feature. The strike line of a bed, fault, or other planar feature is a line representing the intersection of that feature with a horizontal plane. On a geologic map, this is represented with a short straight line segment oriented...

. A homocline may be formed by uplift

Tectonic uplift

Tectonic uplift is a geological process most often caused by plate tectonics which increases elevation. The opposite of uplift is subsidence, which results in a decrease in elevation. Uplift may be orogenic or isostatic.-Orogenic uplift:...

 of coastal plain

Coastal plain

A coastal plain is an area of flat, low-lying land adjacent to a seacoast and separated from the interior by other features. One of the world's longest coastal plains is located in eastern South America. The southwestern coastal plain of North America is notable for its species diversity...

 sediments, or as a limb of a large dome

Dome (geology)

In structural geology, a dome is a deformational feature consisting of symmetrically-dipping anticlines; their general outline on a geologic map is circular or oval...

 or fold

Fold (geology)

The term fold is used in geology when one or a stack of originally flat and planar surfaces, such as sedimentary strata, are bent or curved as a result of permanent deformation. Synsedimentary folds are those due to slumping of sedimentary material before it is lithified. Folds in rocks vary in...

. On a topographic map

Topographic map

A topographic map is a type of map characterized by large-scale detail and quantitative representation of relief, usually using contour lines in modern mapping, but historically using a variety of methods. Traditional definitions require a topographic map to show both natural and man-made features...

, homoclines exhibit nearly parallel elevation

Elevation

The elevation of a geographic location is its height above a fixed reference point, most commonly a reference geoid, a mathematical model of the Earth's sea level as an equipotential gravitational surface ....

 contour lines that show a steady change in elevation in a given direction.

A homoclinal ridge, or strike ridge, is a stratigraphic landform typically characterized by a steep escarpment

Escarpment

An escarpment is a steep slope or long cliff that occurs from erosion or faulting and separates two relatively level areas of differing elevations.-Description and variants:...

 or scarp slope (also known as a strike slope or antidip slope) on the side that cuts across the strata, and a more gentle dip slope

Dip slope

A dip slope is a geological formation often created by erosion of tilted strata. Dip slopes are found on homoclinal ridges with one side that is steep and irregular and another side, the dip slope, that is generally planar with a dip parallel to the bedding...

 on the side of the ridge

Ridge

A ridge is a geological feature consisting of a chain of mountains or hills that form a continuous elevated crest for some distance. Ridges are usually termed hills or mountains as well, depending on size. There are several main types of ridges:...

 that follows the dip. A homoclinal ridge forms when tilted strata with dissimilar erosional resistance erode

Erosion

Erosion is when materials are removed from the surface and changed into something else. It only works by hydraulic actions and transport of solids in the natural environment, and leads to the deposition of these materials elsewhere...

 at different rates. The more durable erosion resistant materials are the slope-former

Slope-former

The term slope-former is a geologic term indicating that a unit of bedrock is less resistant to erosion than overlying or underlying units and consequently outcrops have low slope angles. It may be contrasted with cliff-former. Typical slope formers include shales, and limestones in humid...

s found on the typically shallower back slope, while more easily eroded layers are the cliff-former

Cliff-former

The term cliff-former is a geologic term indicating that a unit of bedrock is more resistant to erosion than overlying or underlying units and consequently outcrops have high slope angles. It is more or less equivalent to ridge-former, and may be contrasted with slope-former. In humid...

s. These ridges are well formed when harder sandstones and limestones are interbedded with softer shales, siltstones, and mudstones in tilted exposed strata, resulting in differential erosion. Ridges associated with homoclines having steeply tilted strata, and exhibiting nearly symmetrical cross-section, are also known as hogback ridges

Hogback (geology)

A hogback is a homoclinal ridge, formed from a monocline, composed of steeply tilted strata of rock protruding from the surrounding area. The name comes from the ridge resembling the high, knobby spine between the shoulders of a hog. In most cases, the two strata that compose a hogback are...

; those with gently tilting strata, with highly asymmetric profiles, are known as cuesta

Cuesta

In structural geology and geomorphology, a cuesta is a ridge formed by gently tilted sedimentary rock strata in a homoclinal structure. Cuestas have a steep slope, where the rock layers are exposed on their edges, called an escarpment or, if more steep, a cliff...

s.
Homoclinal ridges differ from synclinal

Syncline

In structural geology, a syncline is a fold, with younger layers closer to the center of the structure. A synclinorium is a large syncline with superimposed smaller folds. Synclines are typically a downward fold, termed a synformal syncline In structural geology, a syncline is a fold, with younger...

 or anticlinal

Anticline

In structural geology, an anticline is a fold that is convex up and has its oldest beds at its core. The term is not to be confused with antiform, which is a purely descriptive term for any fold that is convex up. Therefore if age relationships In structural geology, an anticline is a fold that is...

 ridges, in that they have strata dipping in only one direction. Most of the stratigraphic ridges in the Ridge-and-Valley Appalachians

Ridge-and-valley Appalachians

The Ridge-and-Valley Appalachians, also called the Ridge and Valley Province or the Valley and Ridge Appalachians, are a physiographic province of the larger Appalachian division and are also a belt within the Appalachian Mountains extending from southeastern New York through northwestern New...

 of the eastern United States

Eastern United States

The Eastern United States, the American East, or simply the East is traditionally defined as the states east of the Mississippi River. The first two tiers of states west of the Mississippi have traditionally been considered part of the West, but can be included in the East today; usually in...

 are homoclinal ridges.

Etymology

Homocline was introduced as a new term at the 1915 meeting of the Geological Society of America

Geological Society of America

The Geological Society of America is a nonprofit organization dedicated to the advancement of the geosciences. The society was founded in New York in 1888 by Alexander Winchell, John J. Stevenson, Charles H. Hitchcock, John R. Proctor and Edward Orton and has been headquartered at 3300 Penrose...

, but its precise definition and usage have been inconsistent, as was the case with the term monocline before then. Both terms have been used to describe "beds dipping in one direction" and a "one-limbed flexure", with different authors making incompatible distinctions. Henry Darwin Rogers

Henry Darwin Rogers

Henry Darwin Rogers FRS FRSE was an American geologist.-Biography:Rogers was born at Philadelphia. His middle name was given him in honor of Erasmus Darwin, of whose poem “The Botanic Garden” his father was a great admirer...

introduced the term monoclinal in 1842, and it supplanted the previously used term uniclinal, but is now considered obsolete.