Minggu, 23 Januari 2011

niagara falls

From Wikipedia, the free encyclopedia


The Niagara Falls are voluminous waterfalls on the Niagara River, straddling the international border between the Canadian province of Ontario and the U.S. state of New York. The falls are 17 miles (27 km) north-northwest of Buffalo, New York and 75 miles (121 km) south-southeast of Toronto, Ontario, between the twin cities of Niagara Falls, Ontario, and Niagara Falls, New York.

Niagara Falls is composed of two major sections separated by Goat Island: the Horseshoe Falls, which today is entirely on the Canadian side of the border,[1] 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.

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,[2] and almost 4 million cubic feet (110,000 m³) on average. It is the most powerful waterfall in North America.[3]

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.
Contents
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* 1 Characteristics
* 2 Geology
* 3 History
* 4 Impact on industry and commerce
o 4.1 Power
o 4.2 Transport
* 5 Preservation efforts
* 6 In entertainment and popular culture
o 6.1 Over The Falls
o 6.2 Movies and television
o 6.3 Music
o 6.4 Literature
* 7 Tourism
o 7.1 American side
o 7.2 Canadian side
* 8 See also
* 9 References
* 10 Footnotes
* 11 External links
o 11.1 Fiction
o 11.2 Non-Fiction


Characteristics

Niagara Falls is divided into the Horseshoe Falls and the American Falls. The Horseshoe Falls drop about 173 feet (53 m), and 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 volume of water approaching the falls during peak flow season may sometimes be as much as 202,000 cubic feet (5,700 m3) per second.[4] 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).[5] Viewpoints on the American shore generally are astride or behind the falls. The falls face directly toward the Canadian shore.
Geology

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.[6] Scientists believe 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 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.
Aerial view of Niagara Falls, showing parts of Canada and the United States

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.

The Niagara Falls at one time in history 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.[7] 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.[8]
History
1837 woodcut of Falls, from États Unis d'Amérique by Roux de Rochelle.

There are differing theories as to the origin of the name of the falls. According to Iroquoian scholar Bruce Trigger, "Niagara" is derived from the name given to a branch of the locally residing native Neutral Confederacy, who are described as being called the "Niagagarega" people on several late 17th century French maps of the area.[9] According to George R. Stewart, it comes from the name of an Iroquois town called "Ongniaahra", meaning "point of land cut in two".[10]

A number of figures have been suggested as first circulating an eyewitness description of Niagara Falls. Frenchman Samuel de Champlain visited the area as early as 1604 during his exploration of Canada, and members of his party reported to him the spectacular waterfalls, which he described in his journals. Finnish-Swedish naturalist Pehr Kalm explored the area in the early 18th century and wrote of the experience. The consensus honoree is Belgian Father Louis Hennepin, who observed and described the falls in 1677, earlier than Kalm, after traveling with explorer René Robert Cavelier, Sieur de la Salle, thus bringing the falls to the attention of Europeans. Further complicating matters, there is credible evidence that French Jesuit Reverend Paul Ragueneau visited the falls some 35 years before Hennepin's visit, while working among the Huron First Nation in Canada. Jean de Brébeuf also may have visited the falls, while spending time with the Neutral Nation.[11]
Man and woman on Canadian side of Niagara Falls, circa 1858
Maria Spelterini crossing the Niagara gorge on a tightrope on July 4, 1876

During the 18th century, tourism became popular, and by mid-century, it was the area's main industry. Napoleon Bonaparte's brother Jérôme visited with his bride in the early 19th century.[12] In 1837 during the Caroline affair a rebel supply ship, the Caroline, was burned and sent over the falls. In 1848, the falls actually went dry; no water (or at best a trickle) fell for as much as 40 hours. Waterwheels stopped, mills and factories simply shut down for having no power.[13] Later that year demand for passage over the Niagara River led to the building of a footbridge and then Charles Ellet's Niagara Suspension Bridge. This was supplanted by German-born John Augustus Roebling's Niagara Falls Suspension Bridge in 1855. After the American Civil War, the New York Central railroad publicized Niagara Falls as a focus of pleasure and honeymoon visits. With increased railroad traffic, in 1886, Leffert Buck replaced Roebling's wood and stone bridge with the predominantly steel bridge that still carries trains over the Niagara River today. The first steel archway bridge near the falls was completed in 1897. Known today as the Whirlpool Rapids Bridge, it carries vehicles, trains, and pedestrians between Canada (through Canadian Customs Border Control) and the U.S.A. just below the falls. In 1941 the Niagara Falls Bridge Commission completed the third current crossing in the immediate area of Niagara Falls with the Rainbow Bridge, carrying both pedestrian and vehicular traffic between the two countries and Canadian and U.S. customs for each country.


After the First World War, tourism boomed again as automobiles made getting to the falls much easier. The story of Niagara Falls in the 20th century is largely that of efforts to harness the energy of the falls for hydroelectric power, and to control the development on both sides that threaten the area's natural beauty.

A team from the U.S. Army Corp of Engineers dammed the falls in June 1969 in order to clear rock from the base of the falls. Rockslides had caused a significant buildup of rock at the bottom of the American side of the falls, and the engineers were to clean up the rock and repair some faults to prevent eventual erosion of the American side of the waterfall. A temporary dam was constructed to divert the flow of water to the Canadian side; the dam measured 600 feet (180 m) across and was made of nearly 30,000 tons of rock. The engineers cleared the rock debris and tested for safety, finishing the project in November of that year. The temporary dam was blown up to restore water flow.[14]

Before the late 20th century the northeastern end of the Horseshoe Falls was in the United States, flowing around the Terrapin Rocks, which was once connected to Goat Island by a series of bridges. In 1955 the area between the rocks and Goat Island was filled in, creating Terrapin Point.[15] In the early 1980s the United States Army Corps of Engineers filled in more land and built diversion dams and retaining walls to force the water away from Terrapin Point. Altogether 400 feet (120 m) of the Horseshoe Falls was eliminated, including 100 feet (30 m) on the Canadian side. As a result, the Horseshoe Falls is now entirely in Canada.[1]
Impact on industry and commerce
American Falls (large waterfall on the left) and Bridal Veil Falls (smaller waterfall on the right)
Power

The enormous energy of Niagara Falls has long been recognized as a potential source of power. The first known effort to harness the waters was in 1759, when Daniel Joncaire built a small canal above the falls to power his sawmill. Augustus and Peter Porter purchased this area and all of American Falls in 1805 from the New York state government, and enlarged the original canal to provide hydraulic power for their gristmill and tannery. In 1853, the Niagara Falls Hydraulic Power and Mining Company was chartered, which eventually constructed the canals which would be used to generate electricity. In 1881, under the leadership of Jacob Schoellkopf, Niagara River's first hydroelectric generating station was built. The water fell 86 feet (26 m) and generated direct current electricity, which ran the machinery of local mills and lit up some of the village streets.
Canadian Horseshoe falls as viewed from Skylon Tower.

The Niagara Falls Power Company, a descendant of Schoellkopf's firm, formed the Cataract Company headed by Edward Dean Adams,[16] with the intent of expanding Niagara Falls power capacity. In 1890, a five-member International Niagara Commission headed by Sir William Thomson among other distinguished scientists deliberated on the expansion of Niagara hydroelectric capacity based on seventeen proposals, but could not select any as the best combined project for hydraulic development and distribution. When Nikola Tesla, for whom a memorial was later built at Niagara Falls, New York (USA), invented the three-phase system of alternating current power transmission, distant transfer of electricity became possible, as Westinghouse and Tesla had built the AC-power Ames Hydroelectric Generating Plant and proved it effective. In 1893, Westinghouse Electric was hired to design a system to generate alternating current on Niagara Falls, and three years after that, the world's first large AC power system was created, activated on August 26, 1895.[17] The Adams Power Plant Transformer House remains as a landmark of the original system.

By 1896, with financing from moguls like J.P. Morgan, John Jacob Astor IV, and the Vanderbilts, they had constructed giant underground conduits leading to turbines generating upwards of 100,000 horsepower (75 MW), and were sending power as far as Buffalo, 20 miles (32 km) away. Some of the original designs for the power transmission plants were created by the Swiss firm Faesch & Piccard, which also constructed the original 5,000HP waterwheels.

Private companies on the Canadian side also began to harness the energy of the falls. The Government of the province of Ontario, Canada eventually brought power transmission operations under public control in 1906, distributing Niagara's energy to various parts of the Canadian province.

Other hydropower plants were also being built along the Niagara River. But in 1956, disaster struck when the region's largest hydropower station was partially destroyed in a landslide. The landslide drastically reduced power production and tens of thousands of manufacturing jobs were at stake. In 1957, Congress passed the Niagara Redevelopment Act, which granted the New York Power Authority the right to fully develop the United States' share of the Niagara River's hydroelectric potential.[18]

In 1961, when the Niagara Falls hydroelectric project first went on line, it was the largest hydropower facility in the Western world. Today, Niagara is still the largest electricity producer in New York State, with a generating capacity of 2.4 gigawatts (million kilowatts). Up to 375,000 US gallons (1,420 m3) of water a second is diverted from the Niagara River through conduits under the City of Niagara Falls to the Lewiston and Robert Moses power plants. Currently between 50% and 75% of the Niagara River's flow is diverted via four huge tunnels that arise far upstream from the waterfalls. The water then passes through hydroelectric turbines that supply power to nearby areas of Canada and the United States before returning to the river well past the falls.[19] This water spins turbines that power generators, converting mechanical energy into electrical energy. When electricity demand is low, the Lewiston units can operate as pumps to transport water from the lower bay back up to the plant's reservoir, allowing this water to be used again during the daytime when electricity use peaks. During peak electrical demand, the same Lewiston pumps are reversed and actually become generators, similar to those at the Moses plant.[18]


During tourist season, water usage by the power plant is limited by a treaty signed by the U.S. and Canada in 1950 to preserve this natural attraction. On average the Niagara river delivers 1,500,000 US gallons (5,700 m3) of water per second, half of which must flow over the falls during daylight hours from April through October. During other times the power plant may use up to three fourths of the total available water. During winter the Power Authority of New York works with Ontario Power Generation, to prevent ice on the Niagara River from interfering with power production or causing flooding of shoreline property. One of their joint efforts is an 8,800-foot (2,700 m)–long ice boom, which prevents the buildup of ice, yet allows water to continue flowing downstream.[18]

The most powerful hydroelectric stations on the Niagara River are the Sir Adam Beck 1 and 2 on the Canadian side and the Robert Moses Niagara Power Plant and the Lewiston Pump Generating Plant on the American side. Together, Niagara's generating stations can produce about 4.4 GW of power.

In August 2005 Ontario Power Generation, which is responsible for the Sir Adam Beck stations, announced plans to build a new 6.5 miles (10.5 km) tunnel to tap water from farther up the Niagara river than is possible with the existing arrangement. The project is expected to be completed in 2009, and will increase Sir Adam Beck's output by about 182 MW (4.2%).
Panoramic view of American and Horseshoe Fall

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