USA Tourist Attractions (Niagara Falls)

 Top-Rated Tourist Attractions in the USA

The United States is home to some of the most spectacular scenery in the world and some of the most recognizable icons on the planet. Many of the top attractions in the United States are bucket list destinations, drawing visitors from around the world.

Niagara Falls

Niagara Falls is a group of three waterfalls at the southern end of Niagara Gorge, spanning the border between the province of Ontario in Canada and the state of New York in the United States. The largest of the three is Horseshoe Falls, which straddles the international border of the two countries. It is also known as the Canadian Falls. The smaller American Falls and Bridal Veil Falls lie within the United States. Bridal Veil Falls is separated from Horseshoe Falls by Goat Island and American Falls by Luna Island, with both islands in New York.

Formed by the Niagara River, which drains Lake Erie into Lake Ontario before flowing out to the Atlantic Ocean by the Gulf of Saint Lawrence, the combined falls have the highest flow rate of any waterfall in North America that has a vertical drop of more than 50 m (160 ft). During peak daytime tourist hours, more than 168,000 m3 (5.9 million cu ft) of water goes over the crest of the falls every minute. Horseshoe Falls is the most powerful waterfall in North America, as measured by flow rate. Niagara Falls is famed for its beauty and is a valuable source of hydroelectric power. Balancing recreational, commercial, and industrial uses has been a challenge for the stewards of the falls since the 19th century.

Niagara Falls is 27 km (17 mi) northwest of Buffalo, New York, and 69 km (43 mi) southeast of Toronto, between the twin cities of Niagara Falls, Ontario, and Niagara Falls, New York. Niagara Falls was 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 over and through the Niagara Escarpment on the way to the Atlantic Ocean.

Characteristics
Horseshoe Falls is about 57 m (187 ft) high,[5] while the height of the American Falls varies between 21 and 30 m (69 and 98 ft) because of the presence of giant boulders at its base. The larger Horseshoe Falls is about 790 m (2,590 ft) wide, while the American Falls is 320 m (1,050 ft) wide. The distance between the American extremity of Niagara Falls and the Canadian extremity is 1,039 m (3,409 ft).

The peak flow over Horseshoe Falls was recorded at 6,370 m3 (225,000 cu ft) per second.[6] The average annual flow rate is 2,400 m3 (85,000 cu ft) 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, at least 2,800 m3 (99,000 cu ft) per second of water traverse the falls, some 90% of which goes over Horseshoe Falls, while the balance is diverted to hydroelectric facilities and then on to American Falls and Bridal Veil Falls. This is accomplished by employing a weir – the International Control Dam – with movable gates upstream from Horseshoe Falls.
The water flow is halved at night and during the low tourist season winter months and only attains a minimum flow of 1,400 cubic meters (49,000 cu ft) per second. Water diversion is regulated by the 1950 Niagara Treaty and is administered by the International Niagara Board of Control. The verdant green color of the water flowing over 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.

The Niagara River is an Important Bird Area due to its impact on Bonaparte's gulls, ring-billed gulls, and herring gulls. Several thousand birds migrate and winter in the surrounding area.

Geology
The features that became Niagara Falls were created by the Wisconsin glaciation about 10,000 years ago. The retreat of the ice sheet left behind a large amount of meltwater (see Lake Algonquin, Lake Chicago, Glacial Lake Iroquois, and Champlain Sea) that filled up the basins that the glaciers had carved, thus creating the Great Lakes as we know them today. Scientists posit there is an old valley, St David's Buried Gorge, buried by glacial drift, at the approximate location of the present Welland Canal.


Niagara Escarpment (in red). Niagara Falls is center-right between Lake Ontario and Lake Erie.
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 caprock formation is composed of hard, erosion-resistant limestone and dolomite of the Lockport Formation (Middle Silurian). That hard layer of stone eroded more slowly than the underlying materials. Immediately below the caprock lies the weaker, softer, sloping Rochester Formation (Lower Silurian). This formation is 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, Niagara Falls was between present-day Queenstown, Ontario, and Lewiston, New York, but erosion of the crest caused the falls to retreat approximately 6.8 miles (10.9 km) southward. The shape of Horseshoe Falls has changed through the process of erosion, evolving from a small arch to a horseshoe bend to the present-day V-shape. Just upstream from the falls' current location, Goat Island splits the course of the Niagara River, resulting in the separation of Horseshoe Falls to the west from the American and Bridal Veil Falls to the east. Engineering has slowed erosion and recession.
(Wikipedia)