Editing Niagara Escarpment (section)

==Formation==
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[[File:Niagara-Escarpment-Winter-IMG 0626.JPG|right|thumb|275px|Niagara Escarpment in [[Grimsby, Ontario]] from about 1060 metres (3,500 feet) above sea level]]
[[File:Bruce-Trail-bmountain.jpg|thumb|right|275px|A section of escarpment cliff, seen from the Bruce Trail in Ontario]]
[[File:NiagaraEscarpmentOutcroppings LakeMichiganShore.jpg|thumb|right|275px|[[Outcrop]]ping of the escarpment in [[Door County, Wisconsin]] approximately 10 feet (3&nbsp;m) from [[Lake Michigan]]]]
[[File:Niagara Escarpment from above Rattlesnake Point, Milton, Ontario.jpg|thumb|275px|Niagara Escarpment from above Rattlesnake Point, Milton, Ontario]]
[[File:Niagara-Escarpment-Dodge-Co.jpg|thumb|right|275px|alt=Exposure at Dodge County Ledge Park, Wi|Exposure of the escarpment at Dodge County Ledge Park, [[Dodge County, Wisconsin]].]]

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Study of rock exposures and drillholes demonstrates that no displacement of the rock layers occurs at the escarpment, which is not a [[Fault (geology)|fault line]] but the result of unequal [[erosion]]. The escarpment's [[caprock]] is [[Dolomite (mineral)|dolomitic]] [[limestone]], also known as [[Dolomite (rock)|dolostone]], which is more resistant and overlies weaker, more easily eroded [[shale]] as a [[weathering]]-resistant "cap". The escarpment formed over millions of years through a process of differential erosion of these rocks of different hardnesses. Through time the soft rocks weather away or erode by the action of streams. The gradual removal of the soft rocks undercuts the resistant caprock, leaving a cliff or escarpment. The erosional process is most readily seen at [[Niagara Falls]], where the river has quickened the process. It can also be seen at the three [[Genesee River|waterfalls of the Genesee River]] at [[Rochester, New York|Rochester]] (additional resistant rock layers make more than one escarpment in some places). Also, in some places thick glacial deposits, such as the [[Oak Ridges Moraine]], conceal the Niagara Escarpment, such as north of [[Georgetown, Ontario]], where it actually continues under [[glacial till]] and reappears farther north.{{Cn|date=September 2021}}

The dolomite cap was laid down as sediment on the floor of a marine environment. In Michigan, behind (south of) the escarpment, the ''cuesta'' capstone slopes gently to form a [[Michigan Basin|wide basin]], the floor of an [[Ordovician]]-Silurian-age tropical sea. (The escarpment is essentially the remnant shoreline of that sea.) There the constant deposition of minute shells and fragments of biologically-generated [[calcium carbonate]], mixed with sediment washed in by erosion of the virtually lifeless landmasses, eventually formed a limestone layer. During the Silurian period, some magnesium substituted for some of the calcium in the carbonates, slowly forming harder [[Dolomite (rock)|dolomite]] layers in the same fashion. This dolomite basin contains Lakes Michigan, Huron, and Erie. Worldwide sea levels were at their all-time maximum in the Ordovician; as the sea retreated, erosion inevitably began.<ref>{{cite web|url=http://www.uwgb.edu/dutchs/GeologyWisconsin/niagesc.htm|title=The Niagara Escarpment|work=uwgb.edu|access-date=2010-09-07|archive-url=https://web.archive.org/web/20100604132605/http://www.uwgb.edu/dutchs/GeologyWisconsin/niagesc.htm|archive-date=2010-06-04|url-status=dead}}</ref>