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TheNiagara Escarpment is an approximately 1,050-kilometre-long (650-mile) discontinuous, arc-shaped but generally northward-facingescarpment, orcuesta, inCanada and theUnited States. Theescarpment begins south of Lake Ontario and circumscribes the top of theGreat Lakes Basin running fromNew York throughOntario,Michigan, andWisconsin. The escarpment is the cliff over which theNiagara River plunges atNiagara Falls, for which it is named.
The escarpment is aUNESCO WorldBiosphere Reserve. The reserve has the oldest forest ecosystem and trees in eastern North America.[1]
The escarpment is not afault line but the result of unequalerosion. The cliff-forming rock exposed along the escarpment is a belt of limestone and dolomite of theLockport Formation ofSilurian age. The Niagara Escarpment is the most prominent of several escarpments formed in the bedrock of theGreat Lakes Basin. For example, theOnondaga Formation, which runs in a parallel outcrop belt just to the south of the Lockport Formation throughwestern New York andsouthern Ontario, forms a separate escarpment. The Niagara Escarpment traces, and in part shapes, the individual basins and landforms ofLake Ontario,Lake Huron, andLake Michigan.
InRochester, New York, theGenesee River flows through the city in three waterfalls over the scarp face. The escarpment thence runs westward to the Niagara River, forming a deep gorge north of Niagara Falls, which itself cascades over the scarp face. InSouthern Ontario, it spans theNiagara Peninsula, closely following the Lake Ontario shore through the cities ofSt. Catharines andHamilton, where it takes a sharp turn north in the town ofMilton towardGeorgian Bay. It then follows the Georgian Bay shore northwestwards to form the spine of theBruce Peninsula andManitoulin Island, as well as several smaller islands in northern Lake Huron, where it turns westwards into theUpper Peninsula of northern Michigan, south ofSault Ste. Marie. It extends down theGarden Peninsula andPotawatomi Islands into Wisconsin following theDoor Peninsula and then continues more inland from the western coast of Lake Michigan until ending in the southeastern corner ofDodge County.[2]
Study of rock exposures and drillholes demonstrates that no displacement of the rock layers occurs at the escarpment, which is not afault line but the result of unequalerosion. The escarpment'scaprock isdolomiticlimestone, also known asdolostone, which is more resistant and overlies weaker, more easily erodedshale as aweathering-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 atNiagara Falls, where the river has quickened the process. It can also be seen at the threewaterfalls of the Genesee River atRochester (additional resistant rock layers make more than one escarpment in some places). Also, in some places thick glacial deposits, such as theOak Ridges Moraine, conceal the Niagara Escarpment, such as north ofGeorgetown, Ontario, where it actually continues underglacial till and reappears farther north.[citation needed]
The dolomite cap was laid down as sediment on the floor of a marine environment. In Michigan, behind (south of) the escarpment, thecuesta capstone slopes gently to form awide basin, the floor of anOrdovician-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-generatedcalcium 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 harderdolomite 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.[3]
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The escarpment was a major obstacle in the construction of theErie Canal in New York and was traversed by a series of locks; the community which grew up at the site thus became known asLockport, New York.[4]
TheWelland Canal allows ships to traverse the escarpment betweenLake Erie and Lake Ontario on the Niagara Peninsula of Ontario.[5] The canal also allowedSea Lamprey, an invasive species native to Northern Atlantic Ocean, to enter Lake Erie and became a concern for the lake's ecosystem.[6]
In southern Ontario, theBruce Trail runs the length of the escarpment fromQueenston on the Niagara River toTobermory on the Bruce Peninsula.Highway 401, Canada's busiest, also crosses the Niagara Escarpment, beginning its long descent through rolling hills, farmland, and towns west of Milton. Rock exposed on the face of the escarpment can be seen alongHighway 26 fromOwen Sound eastwards towardsMeaford, Ontario.
Hamilton, Ontario is on the escarpment in such a way that the north end of the city is below and the south part above. Commonly referred to as "The Mountain" by its residents, many roads or "mountain accesses" join the urban core below with the suburban expansion above. From 1892 to 1936, theHamilton Incline Railway transported people up and down "The Mountain."
High Cliff State Park in Wisconsin shows how modern and prehistoric humans used the escarpment for not only cultural reasons, but economic gains, as well. A number of different animal and geometriceffigy mounds and the remains of an early 20th-century limestone quarry and kiln are within the park.
Therelief and exposed edge are used by severalwind farms stretching fromPipe toBrownsville in Wisconsin. Wind speeds average 18 mph (about 29 km/h) along this stretch.
The Niagara Escarpment is a prominent Wisconsin feature in Dodge County, southwest of Fond du Lac, Wisconsin; it is known there as "The Ledge" and is in Ledge County Park between Horicon and Mayville, Wisconsin.[7] Some local organizations take their name from it, including The Ledgers, the sports teams atSt. Mary's Springs Academy, which is perched on the side of the escarpment.
Many resorts andski areas in Ontario, Michigan, Wisconsin, and New York are along the escarpment.
Niagara County, New York, near the eastern end of the escarpment, is the site of the 18,000 acres (7,284 ha)Niagara Escarpment AVA (American Viticultural Area).[8] Wines produced in this region include traditionalgrape varieties such asMerlot,Cabernet Franc,Cabernet Sauvignon,Chardonnay, andRiesling, andfruit wines.
Ontario'sNiagara Peninsula is the site of the largestwine-producingappellation (region) in Canada. Cool-climate varieties such as Riesling, Chardonnay, Gamay Noir, Pinot Noir, and Cabernet Franc are among the more than 30varietals produced across 13,600 hectares (33,606 acres). Three subappellations lie along thebenchlands of the Niagara Escarpment:Short Hills Bench,Twenty Mile Bench, andBeamsville Bench.[9]
Northeastern Wisconsin, at the western end of the escarpment, is the site of the 3,800 sq mi (9,800 km2)Wisconsin Ledge AVA.[10] Most of the region's vineyards lie upon the escarpment's eastern-facing slope that rises gently upward from the shores of Lake Michigan to the top of the Ledge, before dropping sharply off into Green Bay, and benefit greatly from constant air movement from Lake Michigan, which stores warmth during the summer. The presence of the lake produces a vacuum of sorts during the growing season: warm air over the lake rises, sucking colder air off the land and creating offshore breezes. Cold air cannot settle over the vineyards and a constant flow of warmer air makes the growing season here longer than in other parts of the state. The escarpment's glacial soils are made up of gravel, sand, and clay over limestone bedrock. Anaquifer provides mineral-rich ground water to the vines, encouraging deep root growth.[11][12]
In February 1990, the Niagara Escarpment was a designated WorldBiosphere Reserve byUNESCO, making it one of 12 in Canada. Development and land use on and adjacent to the escarpment is regulated by theNiagara Escarpment Commission, an agency of the Ontario government.[13]
Cliffs along the scarp face have the oldest forest ecosystem in eastern North America.[14] The oldest tree in Ontario is an eastern white cedar from 688 C.E.[15] The oldest known tree in Wisconsin, a 1,300 year-old eastern white cedar, was found in Brown County.[16]
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