Escarpment

From Fiswiki

Niagara Escarpment is a long escarpment, in the United States and Canada that runs westward from New York State, through Ontario, Michigan, Wisconsin and Illinois. It is composed of the Lockport geological formation of Silurian age, and is similar to the Onondaga geological formation, which runs parallel to it and just to the south, through the western portion of New York and southern Ontario. The escarpment is most famous as the cliff over which the Niagara River plunges to form Niagara Falls, for which it is named.

Escarpment is a steep slope or long cliff that results from erosion or faulting and separates two relatively level areas of differing elevations.

Usually escarpment is used interchangeably with scarp (from the Italian scarpa, shoe).

But some sources differentiate the two terms, where escarpment refers to the margin between two landforms, while scarp is synonymous with a cliff or steep slope. The surface of the steep slope is called a scarp face. Scarps are generally formed by one of two processes: either by differential erosion of sedimentary rocks, or by vertical movement of the Earth's crust along a fault (faulting).

Schematic cross section of a cuesta, dipslopes facing left, and harder rocklayers in darker colors than softer ones. Most commonly, an escarpment is a transition from one series of sedimentary rocks to another series of a different age and composition.

When sedimentary beds are tilted and exposed to the surface, erosion and weathering may occur differentially based on the composition. Less resistant rocks will erode faster, retreating until the point they are overlain by more resistant rock (see cross section schematic). When the dip of the bedding is gentle, a cuesta is formed.

Steeper dips (greater than 30-40°) form hogbacks.