Niagara Falls – USA, North America
The Niagara Falls, located on the Niagara River draining Lake Erie into Lake Ontario, is the collective name for the Horseshoe Falls and the adjacent American Falls along with the comparatively small Bridal Veil Falls, which combined form the highest flow rate of any waterfalls in the world and has a vertical drop of more than 165 feet (50 m). Horseshoe Falls is the most powerful waterfalls (vertical height along with flow rate) in North America. Niagara Falls forms the international border between the Canadian province of Ontario and the U.S. state of New York, also forming the southern end of the Niagara Gorge. The falls are located 17 miles (27 km) north-northwest of Buffalo, New York and 75 miles (121 km) south-southeast of Toronto, between the twin cities of Niagara Falls, Ontario, and Niagara Falls, New York.
Niagara Falls are composed of two major sections, separated by Goat Island: the Horseshoe Falls on the Canadian side and the American Falls on the American side. The smaller Bridal Veil Falls are also located on the American side, separated from the main falls by Luna Island. The international boundary line was originally drawn through Horseshoe Falls in 1819, but the boundary has long been in dispute due to natural erosion and construction.
Niagara Falls were formed when glaciers receded at the end of the Wisconsin glaciation (the last ice age), and water from the newly formed Great Lakes carved a path through the Niagara Escarpment en route to the Atlantic Ocean. While not exceptionally high, the Niagara Falls are very wide. More than 6 million cubic feet (168,000 m3) of water falls over the crest line every minute in high flow, and almost 4 million cubic feet (110,000 m3) on average.
The Niagara Falls are renowned both for their beauty and as a valuable source of hydroelectric power. Managing the balance between recreational, commercial, and industrial uses has been a challenge for the stewards of the falls since the 19th century.
The Horseshoe Falls drop about 173 feet (53 m), while the height of the American Falls varies between 70–100 feet (21–30 m) because of the presence of giant boulders at its base. The larger Horseshoe Falls are about 2,600 feet (790 m) wide, while the American Falls are 1,060 feet (320 m) wide. The distance between the American extremity of the Niagara Falls and the Canadian extremity is 3,409 feet (1,039 m).
The volume of water approaching the falls during peak flow season may sometimes be as much as 202,000 cubic feet (5,700 m3, 5.7 million liters) per second. Since the flow is a direct function of the Lake Erie water elevation, it typically peaks in late spring or early summer. During the summer months, 100,000 cubic feet (2,800 m3) per second of water actually traverses the falls, some 90% of which goes over the Horseshoe Falls, while the balance is diverted to hydroelectric facilities. This is accomplished by employing a weir with movable gates upstream from the Horseshoe Falls. The falls flow is further halved at night, and during the low tourist season in the winter, remains a flat 50,000 cubic feet (1,400 m3) per second. Water diversion is regulated by the 1950 Niagara Treaty and is administered by the International Niagara Board of Control (IJC).
The verdant green colour of the water flowing over the Niagara Falls is a byproduct of the estimated 60 tonnes/minute of dissolved salts and “rock flour” (very finely ground rock) generated by the erosive force of the Niagara River itself. The current rate of erosion is approximately 1 foot (0.30 m) per year down from a historical average of 3 feet (0.91 m) per year. However, it is estimated that 50,000 years from now, even at this reduced rate of erosion, the remaining 20 miles (32 km) to Lake Erie will have been undermined and the falls will cease to exist.
The features that became Niagara Falls were created by the Wisconsin glaciation about 10,000 years ago. The same forces also created the North American Great Lakes and the Niagara River. All were dug by a continental ice sheet that drove through the area, deepening some river channels to form lakes, and damming others with debris. Scientists argue that there is an old valley, buried by glacial drift, at the approximate location of the present Welland Canal.
When the ice melted, the upper Great Lakes emptied into the Niagara river, which followed the rearranged topography across the Niagara Escarpment. In time, the river cut a gorge through the north facing cliff, or cuesta. Because of the interactions of three major rock formations, the rocky bed did not erode evenly. The top rock formation was composed of erosion-resistant limestone and Lockport dolostone. That hard layer of stone eroded more slowly than the underlying materials. The aerial photo on the right clearly shows the hard caprock, the Lockport Formation (Middle Silurian), which underlies the rapids above the falls, and approximately the upper third of the high gorge wall.
Immediately below the hard-rock formation, comprising about two thirds of the cliff, lay the weaker, softer, sloping Rochester Formation (Lower Silurian). This formation was composed mainly of shale, though it has some thin limestone layers. It also contains ancient fossils. In time, the river eroded the soft layer that supported the hard layers, undercutting the hard caprock, which gave way in great chunks. This process repeated countless times, eventually carving out the falls.
Submerged in the river in the lower valley, hidden from view, is the Queenston Formation (Upper Ordovician), which is composed of shales and fine sandstones. All three formations were laid down in an ancient sea, their differences of character deriving from changing conditions within that sea.
About 10,900 years ago, the Niagara Falls was located between present-day Queenston, Ontario, and Lewiston, New York, but erosion of their crest has caused the waterfalls to retreat approximately 6.8 miles (10.9 km) southward. The Horseshoe Falls, which are approximately 2,600 feet (790 m) wide, have also changed their shape through the process of erosion; evolving from a small arch, to a horseshoe bend, to the present day gigantic inverted V. Just upstream from the falls’ current location, Goat Island splits the course of the Niagara River, resulting in the separation of the Canadian Horseshoe Falls to the west from the American and Bridal Veil Falls to the east. Engineering has slowed erosion and recession.
Ships can bypass Niagara Falls by means of the Welland Canal, which was improved and incorporated into the Saint Lawrence Seaway in the middle 1950s. While the seaway diverted water traffic from nearby Buffalo and led to the demise of its steel and grain mills, other industries in the Niagara River valley flourished with the help of the electric power produced by the river. However, since the 1970s the region has declined economically.
The cities of Niagara Falls, Ontario, Canada and Niagara Falls, New York, U.S.A. are connected by two international bridges. The Rainbow Bridge, just downriver from the falls, affords the closest view of the falls and is open to non-commercial vehicle traffic and pedestrians. The Whirlpool Rapids Bridge lies one mile (1.6 km) north of the Rainbow Bridge and the oldest bridge over the Niagara River. Nearby Niagara Falls International Airport and Buffalo Niagara International Airport were named after the waterfall, as were Niagara University, countless local businesses, and even an asteroid.
Peak numbers of visitors occur in the summertime, when Niagara Falls are both a daytime and evening attraction. From the Canadian side, floodlights illuminate both sides of the falls for several hours after dark (until midnight). The number of visitors in 2007 was expected to total 20 million and by 2009, the annual rate was expected to top 28 million tourists per year.
The oldest and best known tourist attraction at Niagara Falls is the Maid of the Mist boat cruise, named for an ancient Ongiara Indian mythical character, which has carried passengers into the rapids immediately below the falls since 1846. Cruise boats operate from boat docks on both sides of the falls.