Niagara Escarpment
Description
The Niagara Escarpment is a landform called a cuesta, where a gently-sloping layer of rock forms a ridge. One side of the ridge has a gentle slope, a so-called dip slope that is essentially the surface of the rock layer. The other side is a steep bluff.
The Niagara Escarpment begins in Watertown New York, USA and continues westerly along the Manitoulin Island in the Province of Ontario, Canada. It continues through Wisconsin and Illinios. It is 1,609 kilometers in length and is the weathered edge of a very ancient sea bottom. Throughout its length from Hamilton, Ontario to Watertown, New York the escarpment ranges from 183 meters (600 feet) above sea level to 189 meters (620 feet) above sea level.
The Niagara Escarpment contains natural communities and rare plants/animals that are restricted to or strongly associated with the near vertical or horizontal exposures of the Escarpment. Numerous migratory birds use the Escarpment in some way during their spring and fall migrations due to the highly visible shoreline and cliff faces. The portion of the Escarpment occurring in Ontario Canada has been designated as a World Biosphere Reserve by the United Nations Education, Scientific and Cultural Organization (UNESCO).
How It Was Formed
The escarpment formed over millions of years through a process of differential erosion of 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. Also, in some places thick glacial deposits conceal the Niagara Escarpment, such as north of Georgetown, Ontario, where it actually continues under glacial till and reappears farther north.
The dolostone cap was laid down as sediment on the floor of a marine environment. In Michigan, behind the escarpment, the cuesta capstone slopes gently to form a wide basin, the floor of an Ordovician-Silurian tropical sea. There the constant depositing of minute shells and fragments of biologically-generated calcium-carbonate, mixed with sediment washing in by erosion of the virtually lifeless landmasses eventually formed a limestone layer. In the Silurian some magnesium substituted for some of the calcium in the carbonates, slowly forming harder sedimentary strata in the same fashion. Worldwide sea levels were at their all-time maximum in the Ordovician; as the sea retreated, erosion began. A dolostone basin contains Lakes Michigan, Huron and Erie. The geological formations under Lakes Superior and Ontario were formed from volcanic rifts.