A fall line (or fall zone ) is the area where an upland region and a coastal plain meet and is noticeable especially where rivers cross it, with resulting rapids or waterfalls . The uplands are relatively hard crystalline basement rock , and the coastal plain is softer sedimentary rock . A fall line often will recede upstream as a river cuts out the uphill dense material, forming "c"-shaped waterfalls and exposing bedrock shoals . Because of these features, riverboats typically cannot travel any farther inland without portaging , unless locks are built. The rapid change of elevation of the water and resulting energy release make the fall line a good location for water mills , grist mills , and sawmills . Seeking a head of navigation with a ready supply of water power, people have long made settlements where rivers cross a fall line.
14-402: The slope of rivers crossing fall zones affected settlement patterns. For example, the fall line represents the inland limit of navigation of many rivers. As such, many cities along a fall line grew as a result of demand for transferring people and goods between land-based and water-based transportation at that place. Download coordinates as: The Atlantic Seaboard Fall Line , or Fall Zone ,
28-460: A fault displaces the ground surface so that one side is higher than the other, a fault scarp is created. This can occur in dip-slip faults , or when a strike-slip fault brings a piece of high ground adjacent to an area of lower ground. Earth is not the only planet where escarpments occur. They are believed to occur on other planets when the crust contracts , as a result of cooling. On other Solar System bodies such as Mercury , Mars , and
42-576: Is a 1,400-kilometre (900-mile) escarpment where the Piedmont and Atlantic Coastal Plain meet in the eastern United States . Much of the Atlantic Seaboard fall line passes through areas where no evidence of faulting is present. The fall line marks the geologic boundary of hard metamorphosed terrain—- the product of the Taconic orogeny —- and the sandy, relatively flat outwash plain of
56-579: The Great Lakes–St. Lawrence Lowlands . Along this line numerous rivers have carved falls and canyons (listed east to west): The River Jacques-Cartier and River Saint-Maurice lack such noticeable feature because they cross the scarp through U-shaped valleys . The falls of the lower Saint-Maurice (as well as those of the River Beauport, in Quebec City ) are due to the fluvial terraces of
70-577: The Moon , the Latin term rupes is used for an escarpment. When sedimentary beds are tilted and exposed to the surface, erosion and weathering may occur. Escarpments erode gradually and over geological time . The mélange tendencies of escarpments results in varying contacts between a multitude of rock types. These different rock types weather at different speeds, according to Goldich dissolution series so different stages of deformation can often be seen in
84-548: The Saint Lawrence river rather than the Laurentian Scarp. Escarpment An escarpment is a steep slope or long cliff that forms as a result of faulting or erosion and separates two relatively level areas having different elevations . The terms scarp and scarp face are often used interchangeably with escarpment . Some sources differentiate the two terms, with escarpment referring to
98-460: The plateau . Scarps are generally formed by one of two processes: either by differential erosion of sedimentary rocks , or by movement of the Earth's crust at a geologic fault . The first process is the more common type: the escarpment is a transition from one series of sedimentary rocks to another series of a different age and composition. Escarpments are also frequently formed by faults. When
112-570: The fall line was often the head of navigation of rivers due to rapids and waterfalls, such as the Little Falls of the Potomac River . Numerous cities were founded at the intersection of rivers and the fall line. U.S. Route 1 links many of the fall line cities. In the USA, Mid-Atlantic and Southern fall line cities include: The Laurentian Upland forms a long scarp line where it meets
126-493: The fault scarp is very prone to erosion. This is especially true if the material being uplifted consists of unconsolidated sediment. Weathering, mass wasting, and water runoff can soon wear down these bluffs, sometimes resulting in V-shaped valleys along runoff channels. Adjacent V-shaped valley formations give the remaining fault spurs a very triangular shape. This formation is known as a triangular facet ; however, this landform
140-425: The fault. Differential movement and erosion may occur either along older inactive geologic faults, or recent active faults . Fault scarps often involve zones of highly fractured rock and discontinuities of hard and weak consistencies of rock. Bluffs can form from upthrown blocks and can be very steep, as in the case of Pakistan's coastal cliffs. The height of the scarp formation tends to be defined in terms of
154-411: The layers where the escarpments have been exposed to the elements. Fault scarp A fault scarp is a small step-like offset of the ground surface in which one side of a fault has shifted vertically in relation to the other. The topographic expression of fault scarps results from the differential erosion of rocks of contrasting resistance and the displacement of land surface by movement along
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#1732765624944168-405: The margin between two landforms , and scarp referring to a cliff or a steep slope. In this usage an escarpment is a ridge which has a gentle slope on one side and a steep scarp on the other side. More loosely, the term scarp also describes a zone between a coastal lowland and a continental plateau which shows a marked, abrupt change in elevation caused by coastal erosion at the base of
182-784: The upper continental shelf, formed of unconsolidated Cretaceous and Tertiary sediments . Examples of the Fall Zone include the Potomac River's Little Falls and the rapids in Richmond, Virginia , where the James River falls across a series of rapids down to the tidal estuary of the James River. Columbia, South Carolina , is similar as well with the Congaree River . Before navigation improvements such as locks,
196-431: The vertical displacement along the fault. Active scarp faults may reflect rapid tectonic displacement and can be caused by any type of fault including strike-slip faults . Vertical displacement of ten meters may occur in fault scarps in volcanic bedrock, but is usually the result of multiple episodic movements of 5 to 10 meters per tectonic event. Due to the dramatic uplift along the fault, which exposes its surface,
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