North America’s strongest waterfall is three falls in one
Niagara Falls joins Horseshoe Falls on the Ontario–New York line with American Falls and Bridal Veil Falls wholly in New York. Together they hold North America’s highest waterfall flow rate and the world’s seventh-largest, pouring more than 168,000 cubic metres per minute over the crest in peak tourist hours.
Horseshoe Falls, the Canadian side of the trio, drops about 57 metres across a crest roughly 790 metres wide, while the 320-metre-wide American Falls plunges only 21 to 30 metres because huge boulders pile at its foot. Goat Island divides Horseshoe from Bridal Veil, and Luna Island parts Bridal Veil from the American Falls. Flow averages 2,400 cubic metres a second and once peaked at 6,370; under a 1950 treaty, water is diverted to hydroelectric plants so that the flow is halved at night and in winter. The vivid green colour comes from some 60 tonnes of dissolved salts and rock flour carried over every minute.
The falls date from the retreat of the last ice sheet about 10,000 years ago, when the new Great Lakes spilled across the Niagara Escarpment. A hard cap of Lockport limestone and dolomite sits above soft Rochester shale; as the river scoured out the shale, blocks of caprock broke away. Roughly 10,900 years ago the brink stood near Queenston and Lewiston, and it has since retreated about 10.9 kilometres south. Erosion that once averaged a metre or more a year has been slowed by engineering to about 30 centimetres, a rate that would bring the falls to Lake Erie, 32 kilometres off, in about 50,000 years.
The river's reluctance to freeze and its place on migration routes draw around 100,000 wintering gulls, with 20,000 to 30,000 seen daily between November and January.
In the 1870s visitors often paid just to glimpse the water, and industry eyed Goat Island. The Free Niagara campaign, led by painter Frederic Church and landscape designer Frederick Law Olmsted, pushed New York to create the Niagara Reservation, its first state park, on 30 April 1885; Ontario opened Queen Victoria Niagara Falls Park that same year. Name theories range from Ongiara, 'thundering water', to Mohawk onyara, 'the neck' of land between the lakes.
Source: Niagara Falls
