A cliff-former is a geological unit of

bedrock In geology, bedrock is solid Rock (geology), rock that lies under loose material (regolith) within the crust (geology), crust of Earth or another terrestrial planet. Definition Bedrock is the solid rock that underlies looser surface mater ...

that is more resistant to

erosion Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is distin ...

than overlying or underlying

strata In geology and related fields, a stratum ( : strata) is a layer of rock or sediment characterized by certain lithologic properties or attributes that distinguish it from adjacent layers from which it is separated by visible surfaces known as ei ...

and consequently produces

outcrop An outcrop or rocky outcrop is a visible exposure of bedrock or ancient superficial deposits on the surface of the Earth. Features Outcrops do not cover the majority of the Earth's land surface because in most places the bedrock or superficial ...

s with high slope angles. It is more or less equivalent to ''ridge-former'', and may be contrasted with

slope-former A slope-former is a unit of bedrock which is less resistant to erosion than overlying or underlying units and consequently results in outcrops with low relative slope angles. It may be contrasted with cliff-former. Typical slope forming litholo ...

. In humid environments,

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates) ...

s are typically cliff-formers. In arid environments,

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...

s are often cliff-formers also. Recent

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 ...

s may be cliff-formers as well. In the

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 ...

of the eastern

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...

the major ridge-formers are the

Tuscarora Tuscarora may refer to the following: First nations and Native American people and culture * Tuscarora people **''Federal Power Commission v. Tuscarora Indian Nation'' (1960) * Tuscarora language, an Iroquoian language of the Tuscarora people * ...

, Pocono, and

Pottsville Pottsville usually refers to the city of Pottsville, Pennsylvania, in the United States. Pottsville may also refer to: Other communities *Pottsville, New South Wales, Australia *Pottsville, Arkansas, United States *Pottsville, Kentucky, United ...

Formations.

References

{{geomorph-stub Erosion landforms Geomorphology